The research, led by Jinfeng Qi and Jianqiang Wu of the Kunming Institute of Botany at the Chinese Academy of Sciences, addresses a stubborn bottleneck in plant functional genomics. Terpene synthases, or TPSs, are the enzymes that convert linear prenyl diphosphate substrates into the enormous diversity of terpenoid structures found across the plant kingdom. The traditional approach to determining what a given TPS produces involves expressing the gene in bacteria such as Escherichia coli and analyzing the products. But bacterial systems come with well-known liabilities: they cannot perform the eukaryotic post-translational modifications that may be essential for enzyme activity, high-level expression often drives misfolded proteins into insoluble inclusion bodies, and the prokaryotic cellular environment lacks the chaperones and folding machinery needed to keep some plant enzymes soluble and active. Generating stable transgenic maize lines to bypass these problems is expensive and slow, given the crop’s recalcitrance to transformation.

Protoplasts—plant cells stripped of their walls by enzymatic digestion—offer an attractive alternative. Exogenous DNA can be delivered into protoplasts by polyethylene glycol-mediated transfection, driving transient expression of genes of interest within 24 to 48 hours. Maize protoplasts have already proven useful for promoter analysis, protein interaction studies, and investigating nonvolatile defensive metabolites such as benzoxazinoids. But nobody had shown whether they could support the study of volatile terpene biosynthesis, which poses a distinct analytical challenge: the products evaporate, making detection and quantification far more delicate than measuring water-soluble compounds. The new work demonstrates that, with the right combination of growth conditions, culture parameters, and extraction chemistry, maize protoplasts can indeed become miniature terpene factories whose output is readily captured and measured.

The first obstacle the team faced was a genuine biological paradox. Protocols for isolating stable maize protoplasts typically call for etiolated seedlings grown in complete darkness, because the large central vacuoles characteristic of skotomorphogenic cells maintain high turgor pressure and help the naked cells survive the mechanical stresses of centrifugation and pipetting. However, light is a critical environmental cue for terpenoid metabolism: it drives plastid development and the accumulation of farnesyl diphosphate, the C15 precursor of sesquiterpenes. When the researchers compared seedlings grown in darkness with those given one, two, three, or eight days of dim light at 4.25 micromoles per square meter per second, they found that the partially greened seedlings accumulated dramatically more precursor and product. After methyl jasmonate treatment, the greenish seedlings released 2.7-fold more (E)-α-bergamotene and 3.8-fold more (E)-β-farnesene than etiolated controls, and farnesyl diphosphate levels rose up to 5.9-fold with eight days of light exposure. The compromise—eight days of dim light—balanced cellular robustness with metabolic competence, resolving what the authors call the light paradox.

Leaf anatomy added a second layer of optimization. The maize leaf is a developmental gradient running from the division-active basal meristem to the fully mature tip. Protoplasts isolated from the base and middle of the second leaf showed excellent integrity and transfection efficiencies above 90 percent with an enhanced green fluorescent protein reporter, but a substantial fraction of protoplasts from the leaf tips ruptured after transfection. The likely explanation lies in cellular architecture: in mature tip cells, the central vacuole has fragmented into smaller vacuoles and the cytoplasm is packed with chloroplasts, undermining osmotic stability and mechanical strength. The base and middle regions of greenish seedling leaves were therefore selected for all subsequent experiments, underscoring how developmental stage alone can make or break a protoplast protocol.

Detecting the volatile products required its own series of refinements. The team compared direct overnight headspace adsorption with solid-phase microextraction against a strategy in which protoplasts are first lysed and extracted with an organic solvent. Extraction with n-hexane or n-pentane vastly outperformed direct adsorption, and n-pentane was chosen for its lower toxicity and greater volatility. The final workflow concentrates the extract, heats it to 65 degrees Celsius to drive volatiles into the headspace, and captures them on a polydimethylsiloxane solid-phase microextraction fiber before gas chromatographic analysis on a Shimadzu GC-2014 system. Culture conditions mattered as well: a nutrient-rich medium supplemented with sucrose, glucose, and Murashige and Skoog salts supported higher terpene accumulation than the standard W5 solution, sealed containers and darkness outperformed light and open vessels, and larger culture volumes helped—in 50-milliliter headspace tubes, (E)-β-farnesene levels ran 60 percent higher than in 2-milliliter tubes.

Promoter choice and cofactor supply further sharpened the system’s sensitivity. When the maize gene ZmTPS10 was expressed from the maize ubiquitin promoter, protoplasts accumulated more (E)-α-bergamotene and (E)-β-farnesene than when the cauliflower mosaic virus 35S promoter drove the same gene. Spraying the mother plants with methyl jasmonate eight hours before protoplast isolation—an approach the authors describe as in planta priming—boosted terpene accumulation in subsequently transfected protoplasts more than tenfold compared with untreated controls, exploiting the intact plant’s metabolic machinery to enrich precursors rather than adding expensive, hydrolysis-prone farnesyl diphosphate directly to the medium. Because all terpene synthases carry a conserved DDxxD domain that binds magnesium, the researchers also tested whether adding 10 millimolar magnesium ions to the culture medium would help. It did: bergamotene rose 2.7-fold and farnesene 2.0-fold, confirming that cofactor availability limits ZmTPS10 activity inside the transfected cells.

To show that the platform extends beyond single-enzyme biochemistry, the team used it to interrogate transcriptional regulation. A previous study had identified ZmMYC2a, a basic helix-loop-helix transcription factor in the jasmonate signaling pathway, as a positive regulator of (E)-α-bergamotene and (E)-β-farnesene biosynthesis. Overexpressing ZmMYC2a in maize protoplasts significantly elevated both volatiles relative to a green fluorescent protein control, demonstrating that the system can resolve regulatory layers as well as catalytic function. The authors argue that the high efficiency of multi-plasmid co-transfection opens the door to reconstructing entire defense signaling cascades—receptor to kinase to transcription factor to structural gene—inside a single batch of cells. Because maize protoplasts provide a homologous cellular environment with the correct cofactors, membranes, and post-translational modification machinery, the resulting data should carry higher physiological fidelity than results from heterologous bacterial or yeast systems.

The implications reach well beyond one crop. Graminaceous staples such as wheat and sorghum share maize’s stubborn resistance to genetic transformation, and a rapid protoplast-based assay could serve as an efficient shortcut for functional gene studies across these species, with potential extension to other non-model plants through optimization of osmotic regulators, enzyme cocktails, and ionic conditions. Ecologically, the stakes are considerable: maize terpene volatiles recruit parasitoid wasps against fall armyworm and other pests above ground, attract entomopathogenic nematodes against the western corn rootworm below ground, and even directly damage the peritrophic matrix of lepidopteran midguts. By shrinking the timeline for assigning function to the roughly 30 TPS genes in the maize genome—about half of which still lack confirmed products—this system promises to accelerate the discovery of defensive chemistry that could inform breeding programs and crop synthetic biology for years to come.

Subject of Research: A maize protoplast transfection system for analyzing the biosynthesis and regulation of volatile terpenoid defense compounds

Article Title: A maize protoplast transfection system for studying the biosynthesis of volatile terpenoids

Article References: Qi, J., Li, M., Hu, Z., Li, R., Li, J., Zhang, M., Ma, C., & Wu, J. (2026). A maize protoplast transfection system for studying the biosynthesis of volatile terpenoids. Crop Health, 4(1), Article 13. https://doi.org/10.1007/s44297-026-00076-5

Image Credits: AI Generated

DOI: 10.1007/s44297-026-00076-5

Keywords: maize, protoplast transfection, terpene synthases, volatile terpenoids, ZmTPS10, methyl jasmonate, plant defense, ZmMYC2a, solid-phase microextraction, secondary metabolism, crop biotechnology, protoplast

The research, led by corresponding author Meiliang Zhou together with lead author Zhen Wang and an international team of collaborators from China and Poland, began from a simple observation about where the solution was likely to be found. China is the center of buckwheat germplasm diversity and the origin of cultivated buckwheat, which means the country holds an extraordinary reservoir of genetic variation across wild and domesticated accessions. According to Zhou, however, no systematic analysis had ever been carried out to determine which of these accessions possessed the morphogenic callus induction and transformation potential needed to serve as recipients for genetic engineering. Without such superior recipient lines, efforts to establish reliable transformation protocols remained largely trial and error.

To fill this gap, the team assembled a diverse panel of 100 Tartary buckwheat accessions collected from wild and cultivated germplasm across northern and southern China as well as the Himalayan region. A phylogenetic analysis of this collection allowed the researchers to map the genetic relationships among the accessions and to organize the diversity into distinct evolutionary clades. This population-level perspective was critical, because it ensured that the subsequent screening would capture the breadth of variation present in the species rather than sampling a narrow slice of it. The approach reflects a growing recognition in crop biotechnology that the choice of recipient genotype is often the single most decisive factor in whether a transformation protocol succeeds or fails.

From the full collection, the researchers selected 20 core accessions representing the distinct phylogenetic clades identified in their analysis. Each of these was then evaluated in detail for its capacity to regenerate plants, with the team measuring three key indicators: the induction rate of callus derived from immature zygotic embryos, the induction rate of proembryogenic cell complexes, known as PECCs, and the proliferation capacity of those complexes. These metrics matter because they describe how readily a genotype can produce actively dividing, developmentally plastic tissue that can be coaxed back into whole plants. Accessions that score highly across these measures are the raw material from which practical transformation platforms can be built, while recalcitrant genotypes consistently frustrate even well-designed protocols.

The screening process identified one accession that stood out clearly from the rest: a superior Tartary buckwheat variety designated G253. This elite line exhibited superior morphogenic callus induction and proliferation capacity, making it an ideal recipient for genetic transformation experiments. Morphogenic callus differs from ordinary callus tissue in that it retains a strong propensity to regenerate into organized structures and ultimately whole plants, rather than simply proliferating as an undifferentiated mass. By establishing an efficient morphogenic callus induction system optimized for G253, the researchers created a reproducible pipeline that takes the crop from embryo-derived tissue to a renewable source of transformable cells.

Building on this foundation, the team established a stable Agrobacterium-mediated transformation platform that enables the generation of transgenic Tartary buckwheat plants. Agrobacterium-mediated transformation remains the workhorse of plant genetic engineering because it integrates foreign DNA into the plant genome in a controlled manner, but its success depends heavily on the physiological state of the target tissue. The morphogenic callus system developed in this study addresses that dependency directly. As lead author Zhen Wang explained, using morphogenic callus for genetic transformation represents a significant advancement in overcoming the challenges specific to buckwheat species, because the tissue provides a uniform, actively dividing cell population with high regenerative capacity that improves the efficiency of gene infection, integration, and regeneration.

In addition to the stable transformation platform, the researchers developed an efficient transient transformation system based on protoplasts derived from the morphogenic callus. Protoplasts, which are plant cells stripped of their cell walls, can take up DNA rapidly and are widely used for quick assays of gene expression, subcellular localization, and gene function. Having a protoplast system derived from the same morphogenic callus tissue used for stable transformation creates a powerful complementary tool: researchers can now rapidly test gene constructs in Tartary buckwheat cells before committing to the longer process of generating stable transgenic lines. This pairing of transient and stable systems within a single genetic background substantially shortens the experimental cycle for functional genomics in the crop.

The significance of the work extends well beyond the laboratory. Tartary buckwheat occupies an important niche as a functional food resource, and its bioactive profile makes it a candidate for nutritional improvement through molecular breeding, whether the goal is enhancing flavonoid content, improving stress tolerance, or refining agronomic traits. Until now, the absence of a dependable transformation system meant that such improvements were largely confined to conventional breeding, which is slow in a crop with a relatively narrow cultivated gene pool and challenging genetics. By providing both the critical germplasm, in the form of G253, and the technological support of a validated transformation and protoplast platform, the study lays the groundwork for accelerating molecular breeding progress across the species.

The study also offers a template for other recalcitrant crops. The strategy employed here, in which broad germplasm screening guided by phylogenetic analysis is used to identify naturally competent genotypes before protocol development begins, contrasts with approaches that attempt to force transformation onto agronomically preferred but biologically uncooperative varieties. By letting the biology of the species guide the selection of recipient material, the researchers avoided years of frustration that often accompanies transformation efforts in stubborn crops. The success with G253 suggests that similar systematic surveys could unlock genetic engineering in other orphan crops and underutilized species, where transformation protocols have lagged far behind those of major staples.

For the buckwheat research community, the immediate impact is practical: a stable platform for generating transgenic plants and a transient system for rapid gene testing now exist where none did before. For consumers and producers, the longer-term promise is that the nutritional and agronomic qualities that make Tartary buckwheat distinctive can now be studied and improved at the molecular level. What was once one of the more genetically intractable functional food crops has, through careful germplasm selection and protocol engineering, become a workable target for modern plant biotechnology.

The concept of recalcitrance in plant tissue culture is worth unpacking, because it explains why Tartary buckwheat resisted genetic improvement for so long. Recalcitrant species fail to respond predictably to the hormonal and environmental cues that normally coax plant cells into dividing, forming embryogenic tissue, and regenerating into complete plants. This behavior is strongly genotype-dependent, meaning that two varieties of the same species can behave entirely differently under identical culture conditions. The genetic basis of this variation is still incompletely understood, but its practical consequence is clear: protocols developed in one accession often transfer poorly, or not at all, to another. This is precisely why the systematic screening approach taken in the new study, rather than refining a protocol on a single arbitrarily chosen variety, represents a methodological shift.

The proembryogenic cell complexes highlighted in the screening metrics deserve particular attention. PECCs are small clusters of cells that have initiated the embryogenic developmental program, and their abundance and vigor are among the most reliable predictors of whether a tissue culture line will regenerate efficiently. In cereals and other grasses, the identification of morphogenic callus lines capable of forming PECCs transformed transformation biology, enabling the standardized platforms that underpin modern molecular breeding in maize, rice, and wheat. Extending this logic to a pseudocereal like buckwheat, which occupies a different branch of the plant kingdom, suggests that the underlying cellular requirements for regenerative competence are more conserved across flowering plants than previously appreciated.

The dual nature of the platform also reflects a broader trend in plant functional genomics. Stable transformation, in which introduced DNA is inherited through subsequent generations, remains indispensable for definitive tests of gene function and for creating improved germplasm, but it is slow and resource-intensive. Transient protoplast systems sacrifice heritability for speed, allowing dozens of constructs to be evaluated within days. The efficiency gain comes from matching the two systems to the same cellular source, which minimizes the confounding that arises when transient assays are performed in tissue physiologically dissimilar to the material used for stable work. Researchers studying flavonoid biosynthesis pathways, including the enzymes that channel precursors toward rutin accumulation, stand to benefit directly from this streamlined workflow.

There is also an agricultural dimension to consider. Buckwheat cultivation is concentrated in marginal highland environments where the crop’s tolerance of poor soils and short growing seasons gives it an advantage over cereals. Molecular tools that permit the introduction of stress-tolerance genes or the fine-tuning of bioactive compound accumulation could help maintain and expand this niche as climate variability intensifies. Moreover, because buckwheat is largely self-pollinating and grown with relatively few registered pesticides, it presents fewer regulatory and ecological complications than many engineered staples, potentially shortening the path from laboratory validation to field evaluation for future improved lines.

Subject of Research: Development of an Agrobacterium-mediated genetic transformation platform for Tartary buckwheat using elite germplasm

Article Title: From elite germplasm to transformation platform: Breaking recalcitrance in Tartary buckwheat

Article References: From elite germplasm to transformation platform: Breaking recalcitrance in Tartary buckwheat. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Tartary buckwheat, genetic transformation, Agrobacterium, morphogenic callus, germplasm screening, protoplast, molecular breeding, plant biotechnology, recalcitrance, functional food, flavonoids, regeneration