The two species at the center of the work, Linum austriacum and Linum alpinum, are recognized as some of the richest natural sources of arylnaphthalene lignans. L. austriacum is among the most productive justicidin B-accumulating species known, while L. alpinum, a rare alpine endemic of European mountain regions, has recently emerged as an additional promising source of the same bioactive lignan. Because harvesting wild plants is constrained by the limited range of these species and the low natural abundance of justicidin B, the research team turned to in vitro root cultures, which combine genetic and biochemical stability with rapid growth and the capacity to maintain specialized metabolic pathways under fully controlled conditions. Root cultures are established from aseptically germinated seedlings and maintained on modified Murashige and Skoog medium supplemented with defined auxins and, in the case of L. alpinum, kinetin and casein hydrolysate, subcultured every 30 days to keep biomass development and metabolic state uniform before each experiment.

Understanding why vitexin was chosen requires a look at the architecture of the phenylpropanoid pathway itself. This central metabolic network originates from phenylalanine and proceeds through cinnamic acid, p-coumaric acid, caffeic acid, ferulic acid, and coniferyl alcohol before the sequential formation of pinoresinol, lariciresinol, and secoisolariciresinol, ultimately yielding arylnaphthalene lignans including justicidin B. Crucially, the same pathway also gives rise to flavonoids and numerous other phenolic compounds, so the relative activity of competing branches plays a decisive role in determining which end products accumulate. Flavonoids have traditionally been regarded as terminal products of phenylpropanoid metabolism, but increasing evidence suggests they also participate in metabolic crosstalk and signaling within the network. Vitexin, a naturally occurring C-glycosyl flavone, is a characteristic specialized metabolite of Linum species: it and related mono- and di-C-glycosyl flavones have been identified in the aerial tissues of cultivated flax, and high-resolution mass spectrometry profiling of other Linum species has revealed vitexin among the major detected compounds. Prior work showing that stress-induced accumulation of phenolics, flavonoids including vitexin, and lignans occurs together in Linum cell cultures further supported the close metabolic relationship between the two branches.

Before any supplementation, the researchers first mapped the endogenous accumulation of justicidin B in untreated root cultures of both species over a 30-day cultivation period, quantifying the compound by liquid chromatography coupled with high-resolution electrospray ionization mass spectrometry using an external calibration curve prepared from purified justicidin B. The two species told strikingly different stories. In L. alpinum root cultures, justicidin B was consistently detected and rose gradually from 0.07 micrograms per milligram dry weight on day 5 to a maximum of 0.12 micrograms per milligram dry weight on day 30, with no early accumulation maximum, indicating a slow and progressive trend. In L. austriacum, justicidin B was already present at relatively high levels during early culture development, reaching 1.19 micrograms per milligram dry weight on day 5, then declined to 0.75 on day 20 and bottomed out at 0.58 on day 25, a dip the authors associate with increased biomass development, before partially recovering to 0.72 by day 30. This profile established that justicidin B accumulation in L. austriacum varies with culture age rather than progressing steadily, and it identified day 25 as a suitable intervention point, a phase of reduced endogenous production where the effect of an external supplement could be cleanly evaluated.

The first supplementation experiment applied vitexin at final concentrations of 1, 3, and 5 micromolar to root cultures of both species on cultivation day 25, with harvest after 5 days of treatment on day 30. Each treatment was performed in triplicate, and ethanol-treated cultures were included as solvent controls to distinguish the effects of vitexin from those of the solvent, since stock solutions were prepared in absolute ethanol and diluted with sterile distilled water immediately before use. The ethanol control proved statistically inert in every comparison, confirming that any changes in justicidin B content could be attributed to the flavonoid itself. The results were species-specific in a way that defied a simple concentration-response curve. In L. alpinum, 1 micromolar vitexin produced the highest justicidin B accumulation at 0.14 micrograms per milligram dry weight, roughly a 1.2-fold increase over the untreated control, while higher concentrations of 3 and 5 micromolar yielded contents comparable to controls, indicating that increasing the dose beyond 1 micromolar did not further enhance accumulation in this species.

L. austriacum responded far more dramatically. Supplementation with 1 micromolar vitexin increased justicidin B content to 0.93 micrograms per milligram dry weight, a tendency that fell just short of statistical significance, and 3 micromolar produced 0.86, but the strongest response came at 5 micromolar, where justicidin B reached 1.30 micrograms per milligram dry weight, an approximately 1.8-fold increase over the untreated control that was highly significant. Notably, 3 micromolar did not produce an intermediate response between 1 and 5 micromolar, so vitexin did not induce a simple dose-dependent pattern across the tested range. The authors interpret this as evidence that the effect depends on the metabolic capacity and physiological state of each root culture system, consistent with the known influence of genotype, culture conditions, and treatment optimization on secondary metabolite production in plant in vitro systems.

Because L. austriacum had shown the stronger response, the team extended the work with a prolonged supplementation experiment using higher concentrations and later cultivation stages. Independent sets of cultures were supplemented with 5 or 10 micromolar vitexin on day 30 and harvested on day 35, or supplemented on day 35 and harvested on day 40, again following 5 days of treatment. On day 35, 10 micromolar vitexin significantly increased justicidin B accumulation to 1.45 micrograms per milligram dry weight, approximately 2.4-fold above the untreated control, the strongest effect recorded anywhere in the study. On day 40, however, the picture reversed: 5 micromolar vitexin left justicidin B levels comparable to controls at 1.24 micrograms per milligram dry weight, and 10 micromolar actually produced a slight reduction to 1.01, lower than both the untreated and ethanol-treated controls. This shift demonstrates that the optimal vitexin concentration changes during culture development and that the response is tightly linked to the physiological state of the cultures, with the same dose that strongly supports accumulation at one stage potentially inhibiting the phenylpropanoid pathway at a later one.

The mechanistic hypothesis the authors propose is what makes the study conceptually novel. Vitexin is not a direct biosynthetic precursor of justicidin B, so the observed increases cannot be explained by precursor feeding in the classical sense. Instead, the external supply of vitexin may act through feedback-related modulation of the flavonoid branch of the phenylpropanoid pathway: flooding the cultures with a flavonoid end product may suppress or partially block further metabolic activity toward flavonoid biosynthesis, allowing shared phenylpropanoid intermediates such as coniferyl alcohol to be preferentially directed toward the lignan branch and ultimately toward arylnaphthalene lignan production. In effect, inhibiting a competitive metabolic pathway promotes justicidin B accumulation, exactly as the study’s title suggests. The cultivation-stage-dependent response in L. austriacum further indicates that this redirection is influenced by the physiological state of the cultures and by the applied concentration, emphasizing the importance of optimizing both treatment timing and dose.

The authors are careful to stress that this mechanism remains hypothetical. Future experiments should include targeted metabolomic profiling of flavonoid and lignan intermediates, expression analysis of key genes involved in both branches, and enzyme activity assays for relevant phenylpropanoid pathway enzymes to clarify whether the increased justicidin B accumulation truly results from redirected metabolic activity toward arylnaphthalene lignan biosynthesis. Such analyses would confirm whether exogenous flavonoid supplementation suppresses flavonoid biosynthesis and promotes justicidin B production at the molecular and enzymatic levels, converting a promising correlation into a demonstrated regulatory interaction.

Even with that caveat, the practical implications are considerable. To the best of current knowledge, this is the first study demonstrating that exogenous supplementation with the flavonoid vitexin can influence justicidin B accumulation in Linum root cultures, introducing a novel strategy for enhancing arylnaphthalene lignan production through flavonoid-mediated regulation of the phenylpropanoid pathway. The findings highlight the importance of species-specific metabolic capacity, vitexin concentration, and treatment timing, with L. austriacum root cultures treated with 10 micromolar vitexin on day 30 delivering the highest fold increase in the study. For a compound with such pronounced pharmacological potential and such limited natural availability, a controlled in vitro system that can be steered toward higher lignan output by a single well-timed flavonoid supplement represents a meaningful step toward sustainable biotechnological production, and it opens a new line of inquiry into how the competing branches of one of plant biology’s central metabolic networks can be manipulated by the very molecules they produce.

Subject of Research: Flavonoid-mediated metabolic rerouting enhances anticancer lignan production in Linum root cultures

Article Title: Inhibition of competitive metabolic pathways promotes lignan accumulation in Linum in vitro root cultures

Article References: Zarev, Y., Nedelcheva, R., & Ionkova, I. (2026). Inhibition of competitive metabolic pathways promotes lignan accumulation in Linum in vitro root cultures. Pharmacia, 73, Article e206408. https://doi.org/10.3897/pharmacia.73.e206408

Image Credits: AI Generated

DOI: 10.3897/pharmacia.73.e206408

Keywords: lignans, justicidin B, Linum, vitexin, phenylpropanoid pathway, plant biotechnology, in vitro root cultures, secondary metabolites, Inhibition, competitive, metabolic, pathways

Fusarium wilt, caused by the soilborne fungus Fusarium oxysporum, is among the most economically damaging diseases of tomato. The pathogen invades the plant’s vascular system, blocking water transport and causing wilting, stunting, and often plant death. Conventional control relies heavily on fungicides, resistant cultivars, and crop rotation, but these approaches face mounting challenges from pathogen adaptability, environmental concerns, and the loss of effective chemical tools. Biological control using beneficial soil microorganisms has emerged as a promising alternative, yet the precise mechanisms by which root-associated bacteria confer systemic resistance have remained incompletely understood, particularly with respect to the metabolic reprogramming that occurs throughout the whole plant.

The research team, led by Zhaoxia Jin, constructed a synthetic bacterial consortium composed of three soil-derived strains: Bacillus velezensis YY13, Bacillus subtilis JN1, and Pseudomonas chlororaphis JN72. These species are well-known root colonizers frequently isolated from disease-suppressive soils. Rather than testing each strain individually, the researchers deliberately assembled them into a synthetic community, or SynCom, and introduced the mixture to tomato roots before challenging the plants with the Fusarium wilt pathogen. This design allowed the team to evaluate how a defined microbial community, rather than a single isolate, influences plant immunity across multiple levels of biological organization.

The results were striking. Plants whose rhizosphere soil had been colonized by the SynCom exhibited a 33.49 percent reduction in disease severity compared with untreated controls, along with significantly enhanced biomass. These agronomic improvements were accompanied by profound shifts in the plant’s secondary metabolism, the branch of biochemistry responsible for producing specialized compounds such as flavonoids, phenylpropanoids, and other defense-related molecules. Using untargeted metabolomics, a technique that profiles thousands of metabolites simultaneously without bias toward known compounds, the researchers discovered that the bacterial consortium triggered distinct metabolic alterations in different plant tissues.

In the roots, the most notable change was a 2.1-fold elevation of feruloyltyramine glycosides, a class of phenylpropanoid conjugates known for their antifungal properties and their role in reinforcing cell walls against pathogen attack. In the leaves, the researchers observed a 1.8-fold accumulation of quercetin-O-rutinoside, a flavonoid glycoside with antioxidant and antimicrobial activities. Perhaps most intriguingly, the team found evidence that the bacterial consortium redirected carbon flux within the phenylpropanoid pathway, shifting resources away from lignin precursors, which are primarily structural, and toward antifungal metabolites that directly inhibit pathogen growth. This metabolic rerouting represents a sophisticated form of resource allocation in which the plant prioritizes chemical defense over structural reinforcement when guided by its bacterial partners.

To understand how these metabolic shifts were orchestrated, the researchers performed transcriptional profiling across different tissues and time points. They found that the reprogramming of gene expression was spatiotemporally specific, meaning that particular genes were activated in particular tissues at particular stages of the interaction. In the roots, genes encoding key enzymes of the phenylpropanoid and flavonoid biosynthesis pathways, including phenylalanine ammonia-lyase (PAL), 4-coumarate-CoA ligase (4CL), and chalcone synthase (CHS), were upregulated early in the response. These enzymes catalyze the initial steps that channel carbon from phenylalanine into the phenylpropanoid network, setting the stage for the production of diverse defense compounds.

Notably, the activation of flavanone 3-hydroxylase (F3H), an enzyme that directs flux toward flavonoid production, occurred later and preferentially in the leaves rather than the roots. This temporal and spatial coordination suggests that the plant first establishes a root-based chemical barrier and then extends its defensive chemistry to aerial tissues, creating a systemic state of heightened alertness. The transcriptional changes were synchronized with the induction of pathogenesis-related (PR) genes mediated by the jasmonic acid and ethylene signaling pathways, two hormone systems that are centrally involved in plant defense against necrotrophic pathogens such as Fusarium. The coupling of secondary metabolism with hormone signaling indicates that the bacterial consortium does not merely stimulate random metabolic activity but instead coordinates a coherent, multi-layered immune response.

One of the most remarkable discoveries of the study concerns the role of root-exuded flavonoids in shaping the rhizosphere microbiome. The researchers found that the SynCom-treated plants released elevated levels of the flavonoids naringenin and quercetin into the surrounding soil. These compounds acted as signaling molecules that reshaped the composition of the rhizosphere microbial community, enriching for members of the phylum Actinobacteria, which accounted for 27 percent of the community, and recruiting plant-protective bacterial genera including Bacillus and Pseudomonas. This finding reveals a self-reinforcing loop in which the initial bacterial inoculum triggers plant metabolic changes that, in turn, attract additional beneficial microbes from the soil, amplifying the defense priming signal through positive feedback involving the jasmonic acid, ethylene, and PR gene pathways.

The authors describe this mechanism as a tripartite defense system operating at three interconnected levels. First, the microbial consortium reprograms phenylpropanoid channeling to prioritize defensive metabolites over structural polymers, effectively reallocating the plant’s biochemical resources toward active chemical warfare against the pathogen. Second, it elicits tissue-specific immune transcription that coordinates root and leaf responses in a temporally precise manner. Third, it sustains resistance over time through flavonoid-mediated microbiome recruitment, ensuring that the protective community is continuously replenished and reinforced. The researchers refer to this self-amplifying cycle as a phyto-microbial loop, a paradigm that extends the concept of ecological feedback loops into the realm of plant immunity and offers a framework for designing more effective synthetic microbial communities for agriculture.

The implications of this work extend well beyond tomato and Fusarium wilt. By demonstrating that a defined three-member bacterial consortium can systemically rewire plant secondary metabolism, redirect metabolic flux, coordinate hormone signaling, and reshape the rhizosphere microbiome, the study provides a blueprint for engineering plant microbiomes that enhance disease resistance across diverse crop systems. As agriculture faces increasing pressure to reduce chemical inputs and adopt sustainable practices, understanding the molecular dialogue between roots, microbes, and soil communities becomes ever more critical. This research not only deepens our fundamental knowledge of plant-microbe interactions but also points toward practical applications in which synthetic communities, informed by the principles of metabolic reprogramming and microbiome feedback, could become powerful tools in the fight against soilborne diseases.

Subject of Research: How a synthetic soil bacterial consortium induces systemic metabolic and immune reprogramming in tomato to enhance resistance against Fusarium wilt

Article Title: Soil-derived bacterial root commensals induce systemic alterations of defence-related secondary metabolism and response in tomato whole plants for favoring resistance against Fusarium wilt

Article References: Jin, Z., Liu, X., Li, B., Gao, X., Chen, L., Chen, X., & Guo, Y. (2026). Soil-derived bacterial root commensals induce systemic alterations of defence-related secondary metabolism and response in tomato whole plants for favoring resistance against Fusarium wilt. Plant and Soil. https://doi.org/10.1007/s11104-026-09138-7

Image Credits: AI Generated

DOI: 10.1007/s11104-026-09138-7

Keywords: Fusarium wilt, tomato, synthetic bacterial consortium, rhizosphere microbiome, phenylpropanoid pathway, flavonoids, defense priming, systemic resistance, jasmonic acid, ethylene, plant secondary metabolism, biological control

The central problem the authors confront is a classic growth–defence trade-off. Anthocyanins are built through the phenylpropanoid–flavonoid pathway, a branching metabolic network that draws on carbon skeletons, energy and chemical precursors that the plant could otherwise invest in grain filling, stem strength or stress resilience. When breeders select for ever-darker grains, they may inadvertently be diverting resources away from yield and quality. The review systematically evaluates whether relationships between anthocyanin content and grain yield, eating quality, processing quality and nutritional quality are synergistic, antagonistic or simply unresolved, and finds that the evidence base is far patchier than the enthusiasm for functional foods would suggest. Field studies of coloured rice under coupled water and nitrogen management have documented genuine trade-offs between grain yield and bioactive substance content, meaning that simply stacking pigment genes is not a free lunch.

To understand why, the authors dig into the molecular machinery. Anthocyanin biosynthesis in rice is orchestrated by the MYB–basic helix–loop–helix–WD40 (MBW) transcriptional complex, a three-part regulatory module whose components determine whether the pathway is switched on, where in the plant it operates and how strongly it runs. In black rice, the key players include the R2R3-MYB factor OsKala3 and its bHLH partner OsKala4, which together drive pigmentation in the pericarp, the outer layer of the grain. The WD40 protein OsTTG1 completes the complex and has been shown to promote anthocyanin accumulation while also feeding into cold-tolerance pathways through CBF transcription factors. Historical work tracing the birth of the black rice gene and its spread by introgression shows that this pigmentation trait arose once and was carried across rice populations, a reminder that the trait is both ancient and genetically fragile.

What makes the new review distinctive is its insistence on spatial precision. Anthocyanins in black rice accumulate predominantly in the outer caryopsis layers, and the authors argue that this spatial organisation is not an accident but a design principle worth exploiting. Rather than constitutive biofortification, in which the entire plant is pushed to produce pigment, they propose targeted biofortification: restricting anthocyanin synthesis to appropriate tissues, appropriate developmental windows and carbon-replete conditions. The logic is metabolic bookkeeping. If pigment production is confined to the grain pericarp during grain filling, when photoassimilate is abundant, the carbon and energy cost can be absorbed without competing with vegetative growth or stress defences. If it is activated indiscriminately across leaves, stems and roots, the burden compounds and yield suffers.

Achieving that precision, however, requires regulatory levers that rice science has not yet fully validated. The review catalogues candidate mechanisms drawn from across the plant kingdom, including epigenetic control through DNA methylation and histone modification, post-transcriptional regulation by microRNAs and long non-coding RNAs, vacuolar transport via glutathione S-transferases and ABC transporters that shuttle pigments to their storage compartment, and environmental signalling through light, temperature, sugar and hormone pathways. Studies in apple, peach, grape and populus have shown how blue-light photoreceptors, ethylene-responsive factors and WRKY transcription factors modulate anthocyanin accumulation in tissue-specific and temperature-dependent ways. But the authors are careful to separate direct rice-grain evidence from evidence obtained in other rice tissues and from cross-species or source–sink hypotheses. The quantitative contributions of auxiliary regulators, transport pathways and environmental signals in black-rice caryopses specifically remain incompletely validated, and both categories of inference require grain-specific causal testing and field validation before they can guide breeding.

This evidentiary discipline shapes the two breeding scenarios the review distinguishes. The first improves existing black-rice cultivars, which already possess endogenous, spatially organised pigmentation pathways. Here the task is fine-tuning: identifying alleles and regulatory variants that deepen pigmentation modestly without destabilising the pathway’s tissue specificity, using tools such as genome-wide association studies, quantitative trait loci mapping and introgression lines. The second, more ambitious scenario reconstructs grain-specific anthocyanin production in elite white-rice backgrounds. This has been demonstrated spectacularly in the case of purple endosperm rice, engineered by stacking transgenes to complete the pathway in the starchy interior of the grain. But the authors caution that such reconstruction may require coordinated pathway completion together with much tighter control of tissue specificity and metabolic burden, because a pathway that leaks into the wrong tissues or runs at the wrong time imposes costs the plant cannot hide.

Modern genome editing offers the toolkit for that control. Base editors and prime editors allow precise, knock-in-free modification of regulatory sequences, and CRISPR-based promoter editing enables fine-tuning of gene expression rather than simple gene knockouts. Synthetic promoter designs, built from comprehensive analyses of plant core promoters, could in principle drive anthocyanin genes only in the pericarp, only during grain filling and only when carbon is plentiful. Inducible regulatory systems could couple pigment synthesis to sugar signalling, so that the pathway activates when photoassimilate supply is high and idles when the plant is stressed. The review also highlights the role of spatial multi-omics, including single-cell and spatial transcriptomics, which can map where each biosynthetic and transport gene is active within the developing grain, replacing bulk measurements that average away the very spatial information breeders need.

Genetics alone, however, will not close the loop. The authors propose a Genotype × Environment × Management framework that treats pigmentation as an emergent property of the whole cropping system. Environmental factors such as light intensity, temperature, nitrogen and water availability are known to shift flavonoid metabolism, and management practices such as alternate wetting and drying irrigation, nitrogen and zinc application, and seed priming alter both yield and grain composition. Work on coloured rice has shown that coupled water and nitrogen conditions modulate the trade-off between grain yield and bioactive content, while integrated management approaches under water-saving irrigation can sustain yield and quality simultaneously. Precision agronomy, informed by rice-specific validation experiments, could therefore be used to steer crops into the carbon-replete conditions under which targeted pigment production is cheapest, effectively managing the metabolic budget from the field side as well as the gene side.

The stakes extend beyond a single specialty grain. Rice feeds billions, and most of those consumers eat polished white rice stripped of its bran and its pigments. Biofortification that delivers anthocyanins, or other health-relevant compounds, into staple grains without yield penalties could shift the nutritional economics of the world’s most important cereal, particularly as climate change intensifies heat, drought and flooding stress that already erode both yield and grain quality. The review’s contribution is less a single discovery than a disciplined roadmap: distinguish what is proven in black-rice grains from what is inferred elsewhere, validate candidate regulators causally in the caryopsis, edit with spatial and temporal precision, and embed the genetics in an agronomic system designed around the plant’s carbon economy. If the framework holds up under field validation, the dark grain of the future may be both more nutritious and more productive, not because breeders forced the plant to do more, but because they taught it to spend its resources exactly where it matters.

Subject of Research: Targeted anthocyanin biofortification and spatial metabolic control in black rice

Article Title: Targeted anthocyanin biofortification in black rice: a review of spatial metabolic control, growth–defence trade-offs and genotype–environment–management design

Article References: Chen, M., Wei, Q., Liu, K., Shi, S., Huang, L., Jin, Z., Zhang, Y., & Harrison, M. T. (2026). Targeted anthocyanin biofortification in black rice: a review of spatial metabolic control, growth–defence trade-offs and genotype–environment–management design. Theoretical and Applied Genetics, 139(11), Article 296. https://doi.org/10.1007/s00122-026-05401-8

Image Credits: AI Generated

DOI: 10.1007/s00122-026-05401-8

Keywords: black rice, anthocyanins, biofortification, MBW transcriptional complex, phenylpropanoid pathway, growth-defence trade-offs, genome editing, spatial multi-omics, genotype-environment-management, grain quality, rice breeding, precision agronomy

Brassinosteroids are steroidal plant hormones that regulate a broad spectrum of growth and stress responses, including cell elongation, photosynthesis, and immunity. Exogenous application of 24-epibrassinolide, often abbreviated EBR, has previously shown promise in reducing disease symptoms in a variety of crops, but the metabolic mechanisms underlying this effect in kiwifruit had remained poorly characterized. Because postharvest fruit cannot rely on the inducible immune systems of growing plants in the same way, and because chemical fungicides face increasing regulatory and consumer pressure, understanding how hormone priming reshapes the fruit’s own chemical arsenal is of considerable practical interest. The new study addresses this gap by treating harvested kiwifruit with EBR, challenging the fruit with B. cinerea, and then tracking the resulting metabolic changes at 24, 48, and 72 hours after infection.

The physiological outcome was clear: EBR treatment significantly reduced lesion development compared with untreated controls. This visible protection provided the starting point for the molecular analysis. The researchers employed an integrated physiological and metabolomic approach, profiling the full complement of differentially accumulated metabolites at each of the three time points. They identified 35 differentially accumulated metabolites at 24 hours, 64 at 48 hours, and 57 at 72 hours, a pattern that itself hints at the dynamics of the response: a modest early shift, a pronounced mid-stage surge, and a sustained but slightly attenuated late phase as the fruit begins to recover metabolically.

To make sense of these hundreds of changing compounds, the team performed KEGG pathway enrichment analysis, which maps individual metabolites onto known biochemical networks. Four core pathways emerged as the backbone of the EBR-induced response: phenylpropanoid and flavonoid biosynthesis, amino acid metabolism, purine and cytokinin signaling, and cuticular and lipid metabolism. Each of these pathways contributes a distinct layer of defense, and their coordinated activation suggests that EBR primes the fruit to deploy chemical barriers, physical barriers, and signaling molecules in a structured sequence rather than as a diffuse stress reaction.

The phenylpropanoid and flavonoid pathways are among the most intensively studied branches of plant chemical defense. They generate a diverse array of secondary metabolites, including lignin precursors, antimicrobial phenolics, and antioxidant flavonoids, many of which directly inhibit fungal growth or reinforce cell walls against penetration. Their enrichment in the EBR-treated fruit indicates that the hormone steers metabolic flux toward the production of antifungal compounds, effectively arming the fruit’s chemical frontline before and during fungal attack. Because B. cinerea is a necrotroph that feeds on dead tissue and exploits oxidative damage, the antioxidant dimension of flavonoid accumulation may be particularly significant, blunting the reactive oxygen bursts that the pathogen uses to kill host cells.

Amino acid metabolism formed the second pillar of the response. Changes in free amino acid pools can influence resistance in several ways: some amino acids serve as precursors for defensive secondary metabolites, others act as signaling molecules that modulate hormone crosstalk, and still others alter the nutritional environment presented to the pathogen. A pathogen attempting to colonize fruit encounters not only preformed and induced antimicrobials but also a host whose nitrogen economy has been rearranged, potentially limiting the availability of the nutrients the fungus needs to establish infection. The study’s finding that amino acid metabolism is a core enriched pathway suggests that EBR treatment extends beyond simple toxin production and touches the fundamental resource allocation of the fruit under siege.

The third pillar, purine and cytokinin signaling, points to the communication layer of the defense response. Purine metabolism underpins energy transfer and nucleotide availability, while cytokinins are hormones classically associated with cell division but increasingly implicated in stress signaling and defense regulation. Their involvement indicates that EBR-treated fruit are not merely accumulating defensive chemicals but actively reconfiguring their signaling networks, coordinating the timing and magnitude of the response across tissues. This signaling activation was most prominent at the mid-stage of the trajectory, consistent with the 48-hour time point showing the largest number of differentially accumulated metabolites.

The fourth pillar, cuticular and lipid metabolism, addresses the physical dimension of defense. The cuticle is the waxy outer layer of the fruit surface and constitutes the first barrier any pathogen must breach. Lipid metabolism also supplies the building blocks for cuticular components and for signaling lipids involved in stress responses. By enriching this pathway, EBR treatment appears to reinforce the fruit’s physical armor at the same time that it stocks the chemical arsenal within. The authors note that this combination of chemical and physical barriers, together with signaling activation and metabolic reallocation, constitutes a potential coordinated defense response rather than a collection of isolated effects.

Perhaps the most conceptually important contribution of the study is its temporal analysis, which uncovered a triphasic metabolic trajectory. In the first phase, at 24 hours, the fruit exhibits early chemical defense priming, laying down the initial metabolic groundwork for resistance. In the second phase, at 48 hours, defense amplification takes hold, with signaling activation and a broad surge in differentially accumulated metabolites corresponding to the peak of the response. In the third phase, at 72 hours, the fruit enters metabolic recovery, as the defensive buildup subsides and resources are presumably reallocated back toward maintaining fruit quality. This staged architecture mirrors the priming-and-amplification logic seen in systemic immunity in growing plants and demonstrates that harvested fruit retain a remarkable capacity for organized, time-dependent metabolic defense when appropriately stimulated.

The practical implications extend in two directions. Scientifically, the study provides a comprehensive metabolomic framework for understanding EBR-mediated resistance, giving researchers a map of the pathways and candidate metabolites that can be targeted in future breeding, treatment optimization, or mechanistic studies. Agriculturally and commercially, the identification of specific defense-related metabolites offers potential biomarkers for selecting or verifying resistant fruit, and supports the development of EBR-based treatments as a component of postharvest disease management in kiwifruit, an approach that could reduce reliance on synthetic fungicides during storage. The work was financially supported by the National Natural Science Foundation of China, the Natural Science Foundation of Chongqing, and postgraduate research innovation projects at Chongqing University of Arts and Sciences, with Zhexin Li and Guohua Liu serving as corresponding authors. As the kiwifruit industry continues to grapple with postharvest losses, this study suggests that the fruit’s own metabolism, when nudged in the right direction at the right time, can be recruited as a powerful ally against one of its most persistent enemies.

Subject of Research: Metabolomic mechanisms of 24-epibrassinolide-induced resistance to gray mold in postharvest kiwifruit

Article Title: EBR-induced metabolic reprogramming contributes to kiwifruit resistance against gray mold

Article References: Luo, J., Li, L., Zhang, D., Wang, X., Zeng, T., Zhong, H., Gong, Z., Zhao, X., Peng, J., Luo, Z., Li, Z., & Liu, G. (2026). EBR-induced metabolic reprogramming contributes to kiwifruit resistance against gray mold. BMC Plant Biology. https://doi.org/10.1186/s12870-026-10140-5

Image Credits: AI Generated

DOI: 10.1186/s12870-026-10140-5

Keywords: kiwifruit, Botrytis cinerea, 24-epibrassinolide, brassinosteroids, gray mold, metabolomics, postharvest disease, plant immunity, phenylpropanoid pathway, flavonoids, disease resistance, plant hormones

The strategic logic behind the approach is what makes it compelling. Rather than surveying genomes uniformly across the plant tree of life, the researchers concentrated their sampling on lineages that sit immediately on either side of key evolutionary forks in grass history. This technique, sometimes described as phylogenetic bracketing, allows investigators to infer the timing of a biochemical innovation by asking a simple comparative question: which organisms on one side of the branch possess the pathway, and which on the other side lack it? If a complete set of pathway genes appears in every descendant of one branch but in none of the closest relatives on the other, the origin of that pathway can be placed, with considerable confidence, in the interval between the two divergence events.

Applied to grasses, this logic yielded a dated origin for distinct starch metabolism. Starch is the dominant storage carbohydrate in plants and the principal caloric source for humanity, yet not all starch is built the same way. Grasses, which include the cereal crops that feed the bulk of the world’s population, assemble their storage and transitory starch with a characteristic suite of enzymes that differs in its composition and regulation from the starch systems of many other flowering plants. By mapping the presence of these enzyme sets onto the grass phylogeny, the study could show that the distinctive grass starch pathway arose in the ancestor of a specific branch of the grass family tree, and not earlier. The innovation, in other words, is not an ancient inheritance from the first flowering plants but a later acquisition that coincided with the diversification of the lineage that would eventually give rise to wheat, rice, maize, and their relatives.

The second gateway the study illuminated concerns lignin, the phenolic polymer that stiffens plant cell walls and enabled land plants to stand upright, conduct water under tension, and colonize dry terrestrial environments. Lignin is the product of the phenylpropanoid pathway, a metabolic assembly line that begins with the deamination of the aromatic amino acid phenylalanine by the enzyme phenylalanine ammonia lyase, universally abbreviated PAL. This reaction strips the amino group from phenylalanine and commits the carbon skeleton to the phenylpropanoid pipeline, from which lignin monomers, flavonoids, and thousands of specialized metabolites flow. PAL is therefore the gatekeeper of the entire pathway, the enzyme whose substrate preference determines which amino acids can enter the aromatic metabolism of the cell.

Here the study made its most mechanistically striking discovery. The genomic neighbourhood of ancestral PAL duplicates, examined across the sampled grass lineages, revealed that the PAL gene family had undergone duplication events whose timing could be anchored to the same phylogenetic framework used for the starch analysis. Duplicate genes are the raw material of metabolic evolution, because one copy can preserve the original function while the other accumulates mutations and explores new chemistry. But whether a duplicate actually acquires a new function depends on the specific amino acid changes that alter the shape and chemistry of the enzyme’s active site, and demonstrating this requires more than sequence comparison alone.

To close that gap, the researchers combined their genomic survey with structural and biochemical analysis of the ancestral and derived PAL enzymes. Structural modelling of the enzyme, informed by known PAL architectures, identified candidate positions where substitutions could plausibly change substrate handling. Biochemical characterization of the reconstructed enzymes then tested those predictions directly, measuring what each enzyme version could and could not do. The result was remarkably clean: two amino acid substitutions were sufficient to convert the substrate preference of the enzyme, opening a route by which tyrosine, rather than exclusively phenylalanine, could feed into phenylpropanoid metabolism.

This finding matters because the two aromatic amino acids are not interchangeable feedstocks. Phenylalanine and tyrosine sit at adjacent positions in the aromatic amino acid biosynthetic pathway, but they carry different side chains, and an ammonia lyase that accepts tyrosine produces a different immediate product, one that can be channeled toward particular classes of phenolic compounds. A tyrosine route into phenylpropanoid metabolism therefore represents a genuine expansion of the metabolic gateway, a new door into the pathway that did not exist in ancestors whose PAL enzymes were restricted to phenylalanine. In grasses, this expanded access has implications for the composition of lignin itself, since grass lignins are notable for incorporating substantial quantities of phenolic constituents derived through routes that other plants use only sparingly.

The evolutionary narrative that emerges from combining these strands is one of coordinated innovation. At a decisive branchpoint in grass ancestry, the lineage did not merely accumulate random sequence drift. It acquired a new starch metabolism with its own enzyme configuration, and it acquired an expanded aromatic gateway through PAL duplication and functional divergence. Both innovations would have reshaped the physiology of the plants that carried them. A distinctive starch metabolism alters how carbon is stored and mobilized across the day-night cycle and during development, while an enlarged phenylpropanoid input changes the raw material available for cell wall reinforcement and chemical defense. Together, these changes could have contributed to the ecological success of the grass lineage, which today covers roughly a third of the terrestrial land surface and supplies the majority of human caloric intake.

Methodologically, the study exemplifies a broader shift in how evolutionary metabolism is investigated. The classical approach, exemplified by landmark work on benzoxazinoid biosynthesis in grasses and by decades of comparative enzymology, identified pathways one at a time through careful biochemistry. The new approach inverts the logic: it starts from a well-resolved phylogeny, samples genomes strategically at branchpoints, identifies gene families whose duplication history coincides with metabolic transitions, and then moves into the laboratory to reconstruct and test the ancestral enzymes. Each step constrains the others. Phylogeny tells biochemistry where to look, and biochemistry confirms or refutes what the phylogeny suggests. The identification of two substitutions that opened the tyrosine route is a case study in how this iterative loop can convert a comparative pattern into a causal molecular mechanism.

The implications extend beyond evolutionary theory. Knowing when and how grasses acquired their distinctive starch and lignin systems provides a rational framework for crop improvement, because it identifies the enzymes and substitutions that define the grass-specific versions of these pathways. Engineers seeking to modify lignin for more efficient biofuel production, or to alter starch quality for food and industrial uses, can now consult an evolutionary record that indicates which enzyme versions are ancestral, which are derived, and which specific amino acid changes produced new functions. The branchpoints of grass evolution, once visible only as splits in a species tree, have thus become annotated waypoints on a metabolic map, marking the precise moments when the gateways of plant chemistry were opened, and pointing the way toward deliberate redesign of the pathways that feed and shelter the modern world.

Subject of Research: Evolutionary origins of grass starch and lignin metabolic pathways revealed through phylogenetic genome sampling and ancestral phenylalanine ammonia lyase enzyme analysis

Article Title: Branchpoints reveal metabolic gateways

Article References: Harding, E. A., Fernie, A. R., & Bulut, M. (2026). Branchpoints reveal metabolic gateways. Nature Plants. https://doi.org/10.1038/s41477-026-02434-1

Image Credits: AI Generated

DOI: 10.1038/s41477-026-02434-1

Keywords: grass evolution, starch metabolism, lignin, phenylpropanoid pathway, phenylalanine ammonia lyase, gene duplication, tyrosine, phylogenetic bracketing, plant metabolism, genome evolution, ancestral enzyme reconstruction, cell wall biosynthesis

The team began with classical plant anatomy, sectioning rhizomes at different ages to see exactly when and where the ring pattern emerges. Their analysis revealed that the rings are not laid down gradually throughout the plant’s life. Instead, they arise during a sharply defined critical period, from 126 to 139 days after germination, which falls in early autumn. During this window, the rhizome undergoes uneven secondary growth, the same kind of lateral thickening that widens tree trunks. Crucially, the growth is not uniform around the organ’s circumference. Localized patches of cork cambium, the meristematic tissue that produces protective periderm, become active in some regions while remaining dormant in others. The result is a segmented architecture in which swollen, lignified bands alternate with constricted zones.

The anatomical work also uncovered a second, more dramatic process: programmed cell death in the cortex, the outer tissue layer of the rhizome. As the secondary xylem, the water-conducting wood at the core, expands outward, it exerts mechanical pressure on the surrounding cortex. The cortical cells, already primed for destruction by the plant’s own genetic instructions, are compressed until they collapse, leaving hollow cavities inside the constriction zones. This combination of localized cork cambium activity, xylem-driven compression and cortical cell death produces the multilayered rings and internal voids that give the rhizome its silkworm appearance. In effect, the plant sculpts itself from the inside out, sacrificing its own cortical tissue to create a segmented, hollow-strengthened organ.

To understand what drives this sculpting at the molecular level, the researchers turned to metabolomics, profiling the full complement of small molecules in the developing rhizomes. The analysis revealed a pronounced shift in carbon allocation toward the phenylpropanoid pathway, the metabolic assembly line that plants use to build lignin, the tough polymer that reinforces cell walls. Lignin precursors such as coniferyl alcohol and its storage form coniferin accumulated substantially during the critical period, providing abundant substrate for secondary wall deposition and the lignification of the forming rings. At the same time, the team measured a decrease in core energy metabolites such as succinate, a key intermediate of the citric acid cycle. This pattern points to a metabolic trade-off: the plant is diverting carbon and energy away from general metabolism and toward structural reinforcement, much as a builder diverts materials from interior finishing to fortify a load-bearing wall.

The transcriptomic side of the study identified who is giving the orders. By sequencing the messenger RNA present in rhizomes across the developmental series, the researchers constructed a regulatory network and found a transcriptional hub composed of three families of transcription factors: NAC, ERF and bHLH. This NAC-ERF-bHLH module, active specifically in the root and rhizome tissue, appears to orchestrate the entire ring-forming process. It activates genes involved in phenylpropanoid and flavonoid biosynthesis as well as genes governing starch metabolism, thereby steering the plant’s carbon flux toward structural construction. In other words, a small set of master regulators coordinates the reallocation of sugars, the ramp-up of lignin synthesis and the mobilization of stored starch, all in service of building the segmented architecture.

The multi-omics integration also linked specific enzyme-coding genes to the visible anatomy. Genes encoding phenylpropanoid enzymes such as phenylalanine ammonia-lyase (PAL) and cinnamate 4-hydroxylase (C4H), the entry points of the lignin pathway, showed expression patterns strongly correlated with the timing of ring formation and the accumulation of lignin precursors. Genes encoding ABC transporters, membrane proteins that shuttle molecules across cell membranes, were likewise correlated with the anatomical and metabolic changes, suggesting a role in moving lignin precursors and other metabolites to the sites of wall deposition. This tight correlation between gene expression, metabolite abundance and tissue structure is what gives the study its persuasive power: three independent layers of evidence all point to the same underlying mechanism.

Why would a plant go to such elaborate lengths? The authors propose that the silkworm-like ring is the product of a carbon flow allocation strategy triggered by early autumn environmental signals. As days shorten and temperatures cool, these signals activate the plant’s phospholipid signaling system, which in turn switches on the NAC-ERF-bHLH transcriptional network. The redirected phenylpropanoid carbon flux leads to lignin precursor accumulation, which regulates both cork cambium activation and secondary xylem proliferation. The lignified rings that result improve the mechanical strength of the rhizome, allowing it to resist compression and maintain its shape in the soil. Meanwhile, the hollow cortex created by cell death may serve as an insulating layer that buffers the organ against heat stress, an adaptation that could matter in the exposed mountain habitats where N. incisum grows.

The compartmentalized structure may also serve the plant’s chemistry. N. incisum accumulates medicinal compounds in its rhizome, and the segmented architecture, with its alternating solid and hollow zones, could allow the plant to store these components in discrete compartments, separating them from the transport streams that move water and nutrients through the xylem. The study’s authors suggest that the combination of lignified rings and a buffered, hollow cortex together maintain organ stability while enabling this compartmentalized storage. If correct, the ring pattern is not merely an aesthetic curiosity but a functional adaptation that couples mechanical engineering with pharmaceutical chemistry in a single organ.

Beyond its evolutionary interest, the work has immediate practical value. Because the rings form during a narrow window in early autumn, growers now have a specific developmental target to aim for when managing cultivation. Understanding the environmental cues and signaling pathways that trigger ring formation could allow farmers to optimize planting schedules, soil conditions and harvest timing to produce rhizomes with the prized silkworm-like morphology. The identified NAC-ERF-bHLH hub and the key biosynthetic genes such as PAL and C4H also provide molecular markers that breeders could use to select lines with strong ring-forming capacity, accelerating the improvement of this rare and increasingly pressured medicinal species. All plant material in the study was cultivated at the team’s controlled experimental base in Tanchang County, Gansu Province, rather than collected from the wild, an approach consistent with conservation concerns for a species whose wild populations face harvesting pressure.

Scientifically, the study is a textbook example of what multi-omics integration can achieve in plant developmental biology. Neither the anatomy alone, nor the metabolite profiles, nor the gene expression data could have revealed the mechanism on their own; it is the convergence of all three that turns a morphological description into a causal model. The finding that a single transcriptional hub can coordinate carbon reallocation, secondary wall deposition and programmed cell death adds to a growing body of evidence that plant architecture is often governed by compact regulatory modules that respond to seasonal signals. For N. incisum, the message of the study is clear: the silkworm-like rings that have made this plant famous in apothecaries for centuries are the visible outcome of an autumn-triggered genetic program that trades energy for armor, hollowing the cortex and hardening the rings in a single coordinated sweep. The research, published open access in BMC Plant Biology, gives both scientists and cultivators a molecular handle on a trait that has been valued but never understood.

Subject of Research: Morphogenesis and molecular regulation of silkworm-like ring formation in Notopterygium incisum rhizomes

Article Title: Research on the morphogenesis of Notopterygium incisum rhizomes and its mechanism: multiomics integration analysis reveals the formation mechanism of silkworm-like rings

Article References: Zhao, W., Gao, J., Chen, H., Zhang, J., Lu, W., & Jin, L. (2026). Research on the morphogenesis of Notopterygium incisum rhizomes and its mechanism: multiomics integration analysis reveals the formation mechanism of silkworm-like rings. BMC Plant Biology. https://doi.org/10.1186/s12870-026-09983-9

Image Credits: AI Generated

DOI: 10.1186/s12870-026-09983-9

Keywords: Notopterygium incisum, rhizome, silkworm-like rings, plant morphogenesis, secondary growth, cork cambium, programmed cell death, lignin, phenylpropanoid pathway, multi-omics, transcription factors, medicinal plant

The study, published in Plant Cell Reports, combined physiology, transcriptomics, metabolomics, and enzyme assays to trace exactly how exogenous trehalose bolsters salt tolerance in tomato seedlings. The findings reveal that hydrogen sulfide acts as a central mediator in trehalose-induced protection, and that the downstream response funnels through two metabolic routes: the phenylpropanoid pathway, a workhorse of plant defense chemistry, and the less celebrated cyanoamino acid metabolism pathway, which processes cyanogenic compounds. The work offers a clearer mechanistic picture of how two stress-protective agents interact, and it hints at practical strategies for shielding crops from salinity.

Trehalose is no stranger to stress biology. This disaccharide, composed of two glucose units, accumulates in an astonishing range of organisms, from resurrection plants that survive near-total desiccation to yeast cells braving heat and dehydration. In plants, trehalose and its phosphorylated precursor trehalose-6-phosphate serve dual roles as osmoprotectants that stabilize proteins and membranes, and as sugar signals that rewire metabolism during stress. Previous studies had shown that spraying tomato seedlings with trehalose improves their performance under salt stress by modulating reactive oxygen species, photosynthesis, and osmolyte synthesis. Hydrogen sulfide, meanwhile, has shed its reputation as merely a toxic, rotten-egg-smelling gas. Over the past two decades, plant biologists have established that H2S functions as a genuine signaling molecule, regulating seed germination, stomatal closure, and a broad spectrum of abiotic stress responses, often through persulfidation, a chemical modification that alters the activity of target proteins.

What remained unknown was how these two protective agents relate to each other when deployed together. The Guangxi team, led by corresponding author Changxia Li with co-first authors Jin Qi and Zhang Zhang, designed a series of experiments to answer that question. They grew tomato seedlings under salt stress and treated them with trehalose alone, with sodium hydrosulfide (NaHS), a donor of hydrogen sulfide, alone, or with both compounds simultaneously. The physiological results were striking: both treatments significantly alleviated salt-induced growth inhibition, but the combined treatment produced the most pronounced protective effect, suggesting the two agents act in complementary or synergistic ways.

To dissect the direction of the relationship, the researchers turned to pharmacology. They applied validamycin A, an inhibitor of trehalose biosynthesis, and hypotaurine, a chemical scavenger that mops up hydrogen sulfide. The logic was simple but powerful: if removing hydrogen sulfide abolishes trehalose’s benefits, then trehalose must depend on the gas to work. The experiments delivered a clear verdict. The protective effect of trehalose was largely dependent on hydrogen sulfide, because scavenging the gas with hypotaurine substantially undermined trehalose-induced salt tolerance. In contrast, the efficacy of the NaHS donor was independent of trehalose, indicating a one-directional dependency: trehalose needs hydrogen sulfide, but hydrogen sulfide does not need trehalose. The authors are careful to note the limits of this interpretation. Their data mainly support a requirement for H2S in trehalose action rather than demonstrating that hydrogen sulfide alone is sufficient to reproduce the full trehalose response, and they call for further functional analyses to clarify the precise hierarchy between the two signals.

With the physiological dependency established, the team moved to the molecular level using RNA sequencing. The transcriptomic analysis showed that trehalose modulates the salt stress response of tomato seedlings at the transcriptional level via hydrogen sulfide, and it pinpointed phenylalanine biosynthesis as a core metabolic target. Phenylalanine is the gateway amino acid for the phenylpropanoid pathway, one of the most important specialized metabolic networks in plants. From phenylalanine, plants build an enormous arsenal of compounds, including lignin, which reinforces cell walls and forms apoplastic barriers against ion intrusion; flavonoids and anthocyanins, which act as antioxidants; and a variety of phenolic compounds that buffer oxidative damage. The second pathway flagged by the analysis was cyanoamino acid metabolism, the route that produces and processes cyanogenic glycosides, nitrogen-containing defense metabolites derived from amino acids.

The metabolomic data reinforced the transcriptomic picture. Compared with seedlings receiving salt plus trehalose, those that also received the hydrogen sulfide scavenger hypotaurine showed significantly reversed accumulation of protective metabolites. In the phenylpropanoid pathway, the compounds p-coumaryl alcohol and coniferyl alcohol, both monolignols that feed into lignin biosynthesis, accumulated in response to trehalose but dropped back when hydrogen sulfide was removed. In the cyanoamino acid pathway, the cyanogenic glycosides amygdalin and prunasin, compounds more famous for their roles in almond and stone fruit bitterness, followed the same pattern. This is a notable finding because it implicates a pathway usually discussed in the context of herbivore defense in abiotic stress tolerance, adding to a growing body of evidence that cyanogenic metabolism contributes to how plants cope with environmental challenges.

The enzymatic and gene expression data tied the whole story together. The salt plus trehalose treatment significantly elevated the activities of key enzymes in the phenylpropanoid biosynthesis pathway, including 4-coumarate-CoA ligase (4CL), caffeoyl-CoA O-methyltransferase (CCoAOMT), and peroxidase (POD), as well as enzymes in the cyanoamino acid metabolism pathway, namely mandelonitrile lyase (MDL) and beta-glucosidase (bglX). Consistent with these biochemical changes, the transcript levels of the corresponding encoding genes, including 4CL1, CCoAOMT, POD9, POD43, MDL3, and bglX1, were significantly upregulated. When hypotaurine was added to scavenge hydrogen sulfide, the trehalose-induced enhancement of both enzyme activities and gene expression was significantly reversed. At the molecular level, this confirms that hydrogen sulfide sits upstream of these metabolic changes, serving as a central mediator through which trehalose exerts its protective influence during salt stress.

Why does this matter beyond the laboratory? Salinity stress imposes a double burden on plants: excess sodium ions are toxic, and the osmotic stress they create makes it harder for roots to take up water. Plants respond with a suite of defenses, including osmolyte accumulation, ion homeostasis, and antioxidant systems that neutralize the reactive oxygen species generated under stress. The phenylpropanoid pathway sits at the heart of several of these defenses, supplying lignin for physical barriers and phenolic compounds for antioxidant protection. If trehalose triggers these defenses only through hydrogen sulfide, then breeding or engineering approaches might target the signaling relay itself, for instance by enhancing H2S production capacity or persulfidation of key regulatory proteins, to amplify a crop’s intrinsic stress response. Alternatively, combined field treatments of trehalose and hydrogen sulfide donors could be optimized to exploit the synergy observed in seedlings, though translating greenhouse pharmacology to open-field agriculture always demands careful validation.

The study also enriches a rapidly expanding literature on hydrogen sulfide as a master regulator of plant stress resilience. Recent work has shown that H2S promotes lateral root formation in peach through persulfidation of the SnRK1α kinase, balances hydrogen sulfide and hydrogen cyanide homeostasis in Arabidopsis under osmotic stress, and modulates phenolic metabolism to alleviate salt stress in tomato. The Guangxi findings slot neatly into this picture while adding a new layer: they position trehalose, a sugar signal, upstream of the gas, and they extend the downstream reach of the gas into cyanoamino acid metabolism, a pathway rarely invoked in salt tolerance research. The authors acknowledge that much remains to be resolved, particularly whether hydrogen sulfide alone can reproduce the complete trehalose response and what the precise hierarchical relationship between the two signals looks like under field conditions. But the core message is already compelling: in salt-stressed tomato seedlings, a protective sugar whispers its instructions through a stinky gas, and the plant listens by building stronger walls and richer chemistry. For a crop that feeds billions and a planet whose farmland grows saltier by the season, that conversation is worth every effort to understand and, ultimately, to harness.

Subject of Research: Hydrogen sulfide-dependent trehalose signaling that enhances salt tolerance in tomato seedlings through phenylpropanoid and cyanoamino acid metabolism

Article Title: H2S-dependent trehalose-induced salt tolerance in tomato involves phenylpropanoid and cyanoamino acid pathways

Article References: Qi, J., Zhang, Z., Li, S., Su, J., Tian, Y., Yu, W., & Li, C. (2026). H2S-dependent trehalose-induced salt tolerance in tomato involves phenylpropanoid and cyanoamino acid pathways. Plant Cell Reports, 45(10), Article 283. https://doi.org/10.1007/s00299-026-03969-5

Image Credits: AI Generated

DOI: 10.1007/s00299-026-03969-5

Keywords: trehalose, hydrogen sulfide, salt stress, tomato, phenylpropanoid pathway, cyanoamino acid metabolism, transcriptomics, plant stress signaling, sodium hydrosulfide, hypotaurine, antioxidant defense, Plant Cell Reports

Allelopathy, the phenomenon in which plants release biochemicals that suppress or stimulate their neighbors, has fascinated ecologists for decades and is increasingly viewed as a source of environmentally benign herbicides. Allelochemicals, which include phenolic acids, flavonoids and other secondary metabolites, interfere with germination, photosynthesis, respiration and nitrogen assimilation in susceptible species. What distinguishes the new study is its effort to connect the full chain of events, from the first burst of reactive oxygen species to the activities of specific enzymes of nitrogen metabolism and the phenylpropanoid pathway, in two weed species that had never previously been analyzed together under lupin allelopathy. The authors argue that this integrated view is essential if allelopathic plants are ever to be deployed deliberately as bioherbicides rather than admired as botanical curiosities.

The team grew seedlings of both weeds and treated them with aqueous leaf extract of Lupinus termis at a range of concentrations, then measured a battery of indicators spanning seed germination, oxidative stress markers, antioxidant defenses and metabolic enzyme activities. The earliest and most striking signal was oxidative. Levels of malondialdehyde, the standard fingerprint of lipid peroxidation, rose markedly in the leaves of both species, as did the concentrations of superoxide radicals and hydrogen peroxide. These reactive oxygen species are normal byproducts of a working metabolism, but when their production outpaces their removal they attack membranes, proteins and nucleic acids. The accumulation of all three markers after extract treatment indicated that the allelochemicals in lupin leaves had pushed the weeds’ cellular chemistry into a state of genuine oxidative stress rather than a transient, easily buffered fluctuation.

Plants are not defenseless against such assaults, and the study documented the weeds’ countermeasures in detail. Total phenolic and flavonoid contents increased pronouncedly in both species following exposure to the lupin extract, a defensive metabolic adjustment that reflects activation of the phenylpropanoid pathway, the assembly line that converts phenylalanine into a diverse arsenal of protective compounds. Phenolics can directly scavenge radicals, chelate metal catalysts of oxidation and reinforce cell walls, so their accumulation is a classic sign that a plant perceives chemical stress and is investing resources in containment. The researchers also tracked the four central enzymes of the antioxidant system: superoxide dismutase, which converts superoxide radicals into hydrogen peroxide; ascorbate peroxidase, which uses ascorbate to reduce that peroxide inside chloroplasts; catalase, which decomposes peroxide in peroxisomes; and glutathione reductase, which regenerates the reduced glutathione that feeds the ascorbate-glutathione cycle.

The behavior of these enzymes turned out to be sharply concentration-dependent, and this is where the study delivers its most instructive twist. At lower concentrations of the lupin extract, the activities of superoxide dismutase, ascorbate peroxidase, catalase and glutathione reductase were markedly stimulated in both weed species, suggesting an adaptive response to moderate oxidative stress in which the antioxidant machinery is upregulated to match the increased radical burden. At higher concentrations, however, the same enzymes were significantly suppressed, indicating direct inactivation or structural damage under excessive allelochemical pressure. In other words, a modest dose of lupin chemistry acts like a training exercise that the weeds can withstand, while a heavy dose disables the very enzymes that would otherwise save them. This biphasic pattern mirrors findings from other allelopathy systems and underscores why concentration control matters enormously in any practical application.

Photosynthetic pigments provided a second window into the damage. The study assessed chlorophylls and carotenoids in the treated leaves, following the established understanding that allelopathic phenolics can inhibit chlorophyll accumulation both by suppressing its synthesis and by accelerating its degradation through enzymes such as chlorophyllase. Pigment loss compounds the oxidative problem, because chloroplasts are simultaneously the main source of reactive oxygen species under stress and a primary victim of them. When the photosynthetic apparatus is compromised, energy interception becomes inefficient, excitation pressure builds in the light-harvesting complexes, and the resulting electron leakage generates still more superoxide. The combination of declining pigments and rising lipid peroxidation in the treated weeds paints a coherent picture of a photosynthetic system under escalating, self-amplifying stress.

Beyond the antioxidant story, the researchers extended their analysis to nitrogen metabolism, an angle that gives the work much of its originality. Nitrogen assimilation depends on a chain of enzymes including nitrate reductase, glutamine synthetase and glutamate synthase, which together convert soil nitrate into the amino acids from which proteins, nucleic acids and chlorophyll are built. Perturbing this chain starves a plant of the building blocks needed to repair stress damage, creating a second front of vulnerability. The study’s novelty, according to the authors, lies precisely in linking the concentration-dependent oxidative stress responses with alterations in nitrogen metabolism and in the enzymes of the phenylpropanoid pathway, thereby showing how a single allelochemical insult reverberates through several biochemical networks at once rather than hitting one target in isolation.

The implications for weed management are considerable. Synthetic herbicides face mounting problems of resistance, residues and regulatory restriction, and allelopathy is repeatedly proposed as a source of bioherbicides and of crop rotations that naturally suppress weeds. Lupinus termis is already cultivated as a grain and forage legume, so its residues are abundantly available as mulch, extract or soil amendment. If the concentration-dependent pattern observed here holds in field settings, lupin-derived preparations could be tuned to push target weeds past the threshold where their antioxidant defenses fail, while the same chemistry at lower intensity might even prime neighboring crops. The authors are careful to frame the work as a foundation: the study is the first to examine lupin leaf extract against these two species together, and translating the greenhouse biochemistry into agronomic practice will require dose calibration, soil chemistry considerations and validation against non-target organisms.

The research also contributes to a broader mechanistic debate about how allelochemicals actually work. Recent reviews have emphasized that perturbation of reactive oxygen species metabolism is a recurring element in the mode of action of many allelochemicals, and the lupin study fits that framework neatly while adding metabolic depth. The biphasic enzyme response suggests that hormesis, the phenomenon in which low doses of a stressor stimulate and high doses inhibit, may govern not only growth but the antioxidant apparatus itself. For biochemists, that makes the four antioxidant enzymes a sensitive dosimeter of allelochemical pressure; for agronomists, it means the difference between a stimulatory and a lethal application may be narrow and must be measured rather than assumed.

What remains to be seen is whether the same signatures appear under natural soil conditions, where microbial degradation, adsorption and leaching continuously reshape the effective dose of allelochemicals. The authors report that the underlying data are available from the corresponding author upon reasonable request, and they declare no competing interests and no external funding for the work. As a piece of basic plant physiology, however, the study stands on its own: it demonstrates that a common Mediterranean lupin carries leaf chemistry strong enough to flood two tenacious weeds with reactive oxygen species, provoke a costly phenolic counterattack, and ultimately break the enzymatic shield that keeps their metabolism running. In the quiet chemical warfare waged between plants, the lupin has just been shown to hold a formidable arsenal.

Subject of Research: Allelopathic effects of Lupinus termis leaf extract on oxidative stress, antioxidant defenses and metabolism of two weed species

Article Title: Allelopathic influence of Lupinus termis leaf extract on photosynthetic pigments, antioxidants and metabolic activities in Euphorbia helioscopia and Chenopodium murale

Article References: El-Shora, H. M., Tawfik, M. M., El-Hosary, E. G., El-Sayyad, G. S., Elkelish, A., & Abdulhakim, K. N. (2026). Allelopathic influence of Lupinus termis leaf extract on photosynthetic pigments, antioxidants and metabolic activities in Euphorbia helioscopia and Chenopodium murale. Plant Biosystems, 160(4), Article 233. https://doi.org/10.1007/s44473-026-00217-2

Image Credits: AI Generated

DOI: 10.1007/s44473-026-00217-2

Keywords: allelopathy, Lupinus termis, Euphorbia helioscopia, Chenopodium murale, oxidative stress, antioxidant enzymes, reactive oxygen species, malondialdehyde, phenylpropanoid pathway, nitrogen metabolism, bioherbicides, photosynthetic pigments

The story begins with an ambitious breeding program. Years earlier, the researchers had crossed mustard, Brassica juncea, with heading Chinese cabbage, Brassica rapa var. pekinensis, using distant hybridization to transfer a purple-leaf trait across species boundaries. That effort produced a germplasm line designated 18M-245, whose foliage carried an intense, uniform purple. The team then took the work a step further, introgressing the same purple trait into flowering Chinese cabbage, Brassica rapa var. parachinensis, through repeated hybridization and backcrossing. The result was a new line, 22M-699, a deep-purple flowering Chinese cabbage that represents both a horticultural achievement and, as it turned out, a powerful tool for dissecting the genetics of pigmentation.

With the purple germplasm in hand, the researchers set out to find its molecular basis. They sequenced a panel of genes known to regulate anthocyanin biosynthesis, comparing the purple line against green relatives. What emerged was a pattern of damage in an unexpected place: the promoter region of BrANL2, the regulatory DNA upstream of the gene that controls when and how strongly it is switched on. The purple line carried insertions and large-fragment structural variations in this promoter, and these alterations measurably impaired the promoter’s transcriptional activity. In practical terms, the mutations silenced the silencer. BrANL2 expression dropped in 22M-699, and with the repressor weakened, the anthocyanin pathway ran at full throttle, painting the leaves deep purple.

The correlation between BrANL2 activity and pigment levels was not a one-off observation tied to the mutation. Under low-temperature conditions, which are well known to stimulate anthocyanin accumulation in Brassica crops, the researchers tracked BrANL2 expression and found it moving in the opposite direction to pigment content. As anthocyanins rose, BrANL2 transcripts fell. This inverse relationship held across conditions, strengthening the case that BrANL2 functions as a genuine negative regulator rather than a coincidental bystander in the pigmentation process.

To establish causation, the team turned to two complementary techniques that map the physical contacts between a transcription factor and the genome. DAP-seq, or DNA affinity purification sequencing, allowed them to identify the genomic sites to which the BrANL2 protein binds. Dual-luciferase reporter assays then tested what happens to gene activity when BrANL2 attaches to those sites. The results were unambiguous. BrANL2 binds directly to the promoters of three genes: BrPAL, which encodes phenylalanine ammonia-lyase; BrC4H, which encodes cinnamate 4-hydroxylase; and Br4CL, which encodes 4-coumarate CoA ligase. In each case, binding repressed expression. These three enzymes sit at the gateway of the phenylpropanoid pathway, the metabolic highway from which anthocyanins, and many other flavonoid compounds, are ultimately derived. By throttling the very first steps of that highway, BrANL2 exerts control over the entire downstream pigment pipeline.

The choice of targets is what makes this discovery technically distinctive. Much of the classical literature on anthocyanin regulation focuses on transcription factors that control the later, committed steps of the pathway, often through the well-characterized MYB-bHLH-WD40 complex that activates genes such as dihydroflavonol reductase and leucoanthocyanidin dioxygenase. BrANL2, by contrast, reaches further upstream, clamping down on the entry point of phenylpropanoid metabolism itself. Repressing PAL, C4H, and 4CL does not merely dim the anthocyanin output; it restricts the flux of raw material into the whole family of phenylpropanoid products, from flavonols to lignin precursors. A regulator positioned at this choke point wields unusually broad influence over plant secondary metabolism.

Genetic validation sealed the argument. When the researchers overexpressed BrANL2 in the purple line 22M-699, the abundant repressor protein overwhelmed the weakened promoter’s deficit and reversed the phenotype: the deeply purple plants lost their pigmentation. Conversely, when BrANL2 was knocked out in a green line of flowering Chinese cabbage, the absence of the brake allowed anthocyanins to accumulate, and the plants turned purple. Gain of function removes the color; loss of function creates it. Few regulatory relationships demonstrate their logic so cleanly in both directions, and the reciprocal experiments rule out alternative explanations in which BrANL2 might merely be a downstream consequence of pigmentation rather than its cause.

The result carries a twist for those familiar with the ANL2 gene family. In Arabidopsis, the original ANTHOCYANINLESS2 gene was identified decades ago as a homeobox gene affecting anthocyanin distribution and root development, and mutations in it leave plants pale, implying a positive role in pigmentation. Recent work in strawberry has also implicated an ANL2-like factor, FaANL2, as a repressor acting through the MYB10 activator. The new study adds a third and more mechanistically distinct chapter: in Chinese cabbage, BrANL2 represses anthocyanin biosynthesis not by silencing another transcription factor but by binding directly to the promoters of structural enzymes at the top of the pathway. The authors note that this suppressive role contrasts with the previously reported positive functions of ANL2-like transcription factors, underscoring how the same gene family can be repurposed across species during evolution.

For breeders, the practical implications are considerable. Purple vegetables command premium prices and attract consumer interest because anthocyanins are associated with antioxidant activity and potential health benefits. Yet generating stable, uniformly purple cultivars has traditionally been slow, relying on chance mutations or laborious crosses. The 22M-699 line itself demonstrates the power of distant hybridization, but the identification of BrANL2 as a repressible switch offers something more precise: a single genetic target whose suppression, whether through promoter editing, knockout, or marker-assisted selection of naturally weakened alleles, could induce purple pigmentation in green cruciferous vegetables. Because the target acts upstream of the pathway, the authors suggest it provides a potential strategy for generating purple materials across cruciferous crops more broadly, from pak choi to broccoli relatives.

There are also broader lessons for plant biology. The study illustrates how structural variation in regulatory DNA, rather than changes in protein-coding sequence, can drive dramatic visible phenotypes. The promoter insertions and large rearrangements in BrANL2 did not alter the protein the gene encodes; they changed where, when, and how strongly the gene is expressed. Such cis-regulatory evolution is increasingly recognized as a major engine of crop diversity, and this work provides a textbook example: a silenced repressor producing one of the most visually dramatic traits in the vegetable aisle. As genome editing tools make it routine to rewrite regulatory DNA, understanding which brakes to release, and which to leave alone, will determine how quickly the next generation of colorful, nutrient-enhanced crops reaches the field.

Subject of Research: Negative regulation of anthocyanin biosynthesis by the BrANL2 transcription factor in purple flowering Chinese cabbage

Article Title: BrANL2 negatively regulates the anthocyanin biosynthesis by depressing BrPAL, BrC4H, and Br4CL in purple flowering Chinese cabbage (Brassica rapa var. parachinensis)

Article References: Yuge, L., Xiaoyun, X., Shuancang, Y., Peirong, L., Weihong, W., Yan, L., Xiuyun, Z., Yaowei, Z., Bin, Z., Jiao, W., Yangjun, Y., Fenglan, Z., Tongbing, S., & Deshuang, Z. (2026). BrANL2 negatively regulates the anthocyanin biosynthesis by depressing BrPAL, BrC4H, and Br4CL in purple flowering Chinese cabbage (Brassica rapa var. parachinensis). Theoretical and Applied Genetics, 139(10), Article 290. https://doi.org/10.1007/s00122-026-05384-6

Image Credits: AI Generated

DOI: 10.1007/s00122-026-05384-6

Keywords: anthocyanin, BrANL2, Brassica rapa, flowering Chinese cabbage, transcription factor, gene regulation, plant breeding, DAP-seq, promoter variation, purple vegetables, phenylpropanoid pathway, cruciferous crops

The research team, led by Marceli Pacan and Agnieszka Kuźniar of The John Paul II Catholic University of Lublin, set out to address a persistent puzzle in agricultural biotechnology: why microbial biostimulants often deliver inconsistent results in the field. Wheat is the world’s third most significant crop and accounts for roughly half of all cereal cultivation in the European Union, so even modest improvements in how beneficial microbes perform could have enormous consequences. The scientists compared two modern winter wheat cultivars, ‘Hondia’ and ‘Tytanika’, with ‘Rokosz’, an ancient spelt wheat valued for its higher protein and mineral content and its adaptation to low-input farming. Their central hypothesis was that the metabolic response to endophyte colonization would depend on the host genotype—a proposition the data dramatically confirmed.

The experimental design was meticulous. In laboratory tests, the researchers first optimized the bacterial cell density and temperature for inoculation, finding that 6.67 × 10⁴ cells per milliliter at 15 to 20 degrees Celsius produced the best seedling vigor. They also screened six biochar carriers made from pine or ash wood at different pyrolysis temperatures, ultimately selecting an ash-wood biochar designated J500, which supported normal seedling growth across all cultivars and proved compatible with commercial fungicide seed dressings. This compatibility matters because real-world farmers apply fungicides alongside seed treatments, and a biopreparation that fails under those conditions would be useless in practice.

The heart of the study was a 40-day greenhouse pot experiment in which inoculated and control seeds of all three cultivars were grown in non-sterilized soil, deliberately preserving the natural soil microbiota. Every five days, the researchers measured the activities of two key defense enzymes: peroxidase (POX), which drives cell wall cross-linking and reactive oxygen scavenging, and phenylalanine ammonia-lyase (PAL), the gateway enzyme of the phenylpropanoid pathway that produces phenolic acids, flavonoids, and lignin precursors. The patterns that emerged were anything but uniform. In ‘Hondia’, POX activity stayed suppressed for most of the experiment and then surged fifteen-fold within just five days at day 40, while PAL activity collapsed to an eleven-fold reduction below control levels. In ‘Rokosz’, the opposite occurred: PAL activity climbed to 11.81 IU per gram fresh weight at day 20—the highest value recorded across all treatments—and remained elevated through the end of the experiment, while POX stayed quietly low.

Untargeted metabolomics using liquid chromatography coupled to quadrupole time-of-flight mass spectrometry revealed the chemistry behind these enzymatic divergences. At day zero, just four days after inoculation, both cultivars shared a common set of exclusively induced metabolites pointing to rapid defense priming: oxidized glutathione, L-tryptophan, allantoin, the coumarin scopoletin, and 12-oxo-phytodienoic acid, a jasmonic acid precursor that functions as a stress-signaling molecule. This early signature demonstrates that the endophytes trigger metabolic activation almost immediately, before any visible growth differences appear. Yet even at this earliest stage, the genotypes differed in character. Spelt ‘Rokosz’ showed a balanced distribution of up- and down-regulated molecular features, whereas ‘Hondia’ displayed a pronounced wave of induction in its non-polar, lipid-rich fraction, with 980 differential features compared to 419 in ‘Rokosz’.

By day 40, the two crops had committed to fundamentally different strategies. Modern ‘Hondia’ accumulated wax esters at extraordinary levels—palmityl palmitate increased nearly forty-fold, and several other long-chain wax esters appeared exclusively in treated plants—suggesting reinforcement of the cuticle, the plant’s outer physical barrier. Alongside this, the cultivar showed extensive remodeling of membrane lipids, including galactolipids and sterol esters, broad accumulation of free amino acids such as tryptophan and N-γ-glutamyl-phenylalanine, and shifts in indole-related metabolism consistent with altered hormonal regulation. Meanwhile, several phenylpropanoid-derived flavonoids were strongly down-regulated, indicating that ‘Hondia’ had shifted away from chemical defense toward enzymatic oxidative management and structural reinforcement.

Ancient spelt ‘Rokosz’ told a different story. Treated plants showed significant enrichment of the phenylpropanoid pathway: p-coumaric acid rose 5.3-fold, trans-cinnamaldehyde 4.6-fold, and compounds such as chlorogenic acid, esculetin, and the flavonoid rutin appeared exclusively in biopreparation-treated samples. HPLC profiling confirmed that vanillic acid and total phenolic acid concentrations increased significantly in ‘Rokosz’ but not in ‘Hondia’. Remarkably, ‘Rokosz’ also accumulated ferulic acid in its leaves at levels comparable to its roots—an unusual pattern for cereals, where phenolics typically concentrate in roots and cell walls—potentially enhancing ultraviolet screening and photoprotection in photosynthetic tissue. The picture is of an ancient grain that channels the microbial partnership into building a dense chemical shield.

Perhaps the most striking statistical finding was convergence: biopreparation treatment reduced the metabolic differences between the two cultivars from 760 differential traits under control conditions to 423 after treatment, a 44.3 percent reduction. In other words, the same microbial inoculant pulled both genotypes toward a shared, microbially induced metabolic state, even as each retained its characteristic strategy. The researchers interpret this as evidence that subspecies-level genetic architecture determines whether endophyte colonization triggers metabolic enhancement, as in spelt, or metabolic moderation, as in modern bread wheat—a distinction consistent with prior work showing that endophytes from wild wheat ancestors can make drought-stressed plants metabolically resemble well-watered controls.

For agriculture, the implications are direct and potentially transformative. Microbial inoculants are increasingly promoted as environmentally friendly alternatives to synthetic fertilizers and pesticides, but their field performance is notoriously variable. This study suggests that much of that variability may stem from genotype-treatment interactions rather than product quality: the identical formulation can produce profoundly different metabolic outcomes depending on the crop’s genetic background. The authors argue for precision agrobiotechnology, in which microbial consortia are matched to individual cultivars and metabolic markers—phenylpropanoids, wax esters, and oxylipin signals such as 12-OPDA—are incorporated into breeding programs to select genotypes with enhanced microbial responsiveness. As climate pressures intensify and the need to reduce chemical inputs grows, understanding these hidden metabolic dialogues between crops and their endophytic partners may prove essential to feeding the world sustainably.

Subject of Research: Genotype-specific metabolic and enzymatic responses of wheat and spelt to an endophytic bacterial biopreparation

Article Title: Endophyte-induced metabolic divergence in wheat genotypes: implications for plant–soil interactions

Article References: Pacan, M., Romanyuk, N., Fornal, E., Sumara, A., Nikolaichuk, H., Kruczyńska, A., Goraj, W., & Kuźniar, A. (2026). Endophyte-induced metabolic divergence in wheat genotypes: implications for plant–soil interactions. Plant and Soil. https://doi.org/10.1007/s11104-026-09133-y

Image Credits: AI Generated

DOI: 10.1007/s11104-026-09133-y

Keywords: wheat, spelt, endophytes, metabolomics, plant–soil interactions, biostimulants, phenylpropanoid pathway, PAL, POX, biochar, Bacillus, sustainable agriculture