The research team, led by Liting Deng and corresponding author Junxing Li, employed a comprehensive foodomics approach, combining untargeted metabolomics with transcriptome sequencing to capture a full portrait of what makes fragrant pumpkin leaves taste and smell the way they do. Across untreated leaves, the researchers identified a staggering 1003 metabolites, of which 40 were volatile aroma compounds. The chemical inventory was dominated by six classes: phenolic acids with 150 representatives, amino acids and their derivatives with 93, organic acids with 83, free fatty acids and saccharides with 77 each, and flavonols with 70. Together these six categories accounted for more than 54 percent of everything the team detected.

That catalogue alone carries significant nutritional implications. Phenolic acids and flavonols are among the most intensively studied classes of plant secondary metabolites, widely associated with antioxidant and anti-inflammatory activity in the human diet. Their abundance in pumpkin leaves, the authors argue, supports the vegetable’s positioning as a health-functional food rather than a mere culinary curiosity. But the study’s central question was not simply what the leaves contain—it was how their flavour chemistry responds to intervention, and whether growers could deliberately steer that chemistry toward a more desirable eating experience.

The intervention in question was a combined foliar formulation, a nutrient spray applied directly to the leaf surface. Foliar feeding is an established agronomic technique that bypasses the soil-root system entirely, delivering dissolved nutrients through the cuticle and stomata where they can be absorbed rapidly into metabolic pathways. Because amino acids and aromatic compounds vary dramatically across pumpkin leaf cultivars and growing conditions, flavour has been notoriously difficult to regulate. The new results suggest that this difficulty may be more tractable than previously assumed.

The metabolic consequences of the spray were striking. Of the 28 amino acids and derivatives significantly regulated after treatment, 23 accumulated substantially. The headline result concerned glutamic acid, the amino acid that anchors the savoury umami taste and serves as a fundamental building block of proteins. Glutamic acid rose by 50 percent following foliar feeding, becoming the single most abundant metabolite in the treated leaves. For a vegetable whose culinary appeal depends heavily on savoury depth, that shift represents a meaningful upgrade in eating quality achieved through nothing more exotic than a targeted nutrient spray.

The aroma story proved even more dramatic. The compound 2-acetyl-1-pyrroline, universally abbreviated 2-AP, is the molecule responsible for the taro-like fragrance prized in fragrant pumpkin leaves—and, famously, for the popcorn-like scent of pandan and premium jasmine rice. In the treated leaves, 2-AP levels surged by 189 percent. Simultaneously, (Z)-3-hexen-1-ol, the volatile behind the fresh-cut-grass smell that many consumers find harsh or overly green, dropped by 65.5 percent. The combined effect was a rebalancing of the leaf’s volatile profile toward sweetness and warmth and away from raw vegetal pungency, a shift the authors describe as a prominent improvement in the vegetable’s aroma characteristics.

Understanding how the spray produced these changes required the transcriptomic half of the study. By sequencing gene expression in treated and untreated leaves and integrating those data with the metabolite measurements, the researchers uncovered what appears to be an alternative biosynthetic route to 2-AP—one that runs through the polyamine putrescine rather than the pathways more commonly described in aromatic rice. At the centre of this route sits a gene designated CmoADC, which encodes arginine decarboxylase, the enzyme that channels arginine into putrescine production. Both the metabolite and the gene responded emphatically to foliar feeding: putrescine was up-regulated 2.48-fold, while CmoADC expression jumped 8.33-fold, making it one of the most strongly induced transcripts in the entire dataset.

The regulatory architecture behind these changes appears to involve plant hormones acting through transcription factors. A large proportion of the differentially expressed transcription factors identified in the study were hormone-responsive, hinting that the foliar formulation does not simply dump raw materials into metabolic pools but instead re-tunes the plant’s own signalling networks. Direct measurement of the phytohormone landscape reinforced this interpretation: of the 66 hormone-related compounds the team quantified, 42 were significantly impacted by the treatment, including 18 cytokinin-associated and 11 auxin-associated compounds. Cytokinins are classically linked to nitrogen metabolism and amino acid biosynthesis, which fits neatly with the observed accumulation of glutamic acid and its relatives, while auxin signalling has well-documented connections to secondary metabolism and volatile formation.

For agriculture, the practical message is that flavour quality in leafy vegetables can be engineered through metabolically informed management rather than left to cultivar choice alone. The combined foliar formulation improved amino acid nutrition and umami intensity while simultaneously amplifying the taro-like aroma through a putrescine-dependent 2-AP pathway, giving growers a defined, science-backed lever for quality improvement. Because the treatment acts on the leaf itself and operates within the plant’s existing biochemistry, it offers a relatively low-cost strategy that could be adapted to other fragrant vegetables where 2-AP or related volatiles determine market value.

For plant science, the study adds a compelling piece to the puzzle of how 2-acetyl-1-pyrroline is actually made. The involvement of arginine decarboxylase and putrescine suggests that nitrogen-rich precursors, mobilised in response to nutrient availability and hormone signalling, feed directly into aroma biosynthesis. As pumpkin leaves continue their journey from regional staple to global functional vegetable, work like this demonstrates how metabolomics and transcriptomics together can turn a traditional green into a precisely flavoured, nutritionally optimised crop—one spray at a time.

Subject of Research: Effects of foliar feeding on amino acid and 2-acetyl-1-pyrroline aroma metabolism in fragrant pumpkin leaves

Article Title: Responses of amino acid and aroma metabolism of fragrant pumpkin leaves to foliar feeding: insights from metabolomic and transcriptomic technologies

Article References: Deng, L., Luo, J., Zhao, G., Liu, X., Wu, H., Gong, H., Zheng, X., Wu, X., Dai, Z., Wang, H., Chen, C., Wang, X., Zheng, Y., & Li, J. (2026). Responses of amino acid and aroma metabolism of fragrant pumpkin leaves to foliar feeding: insights from metabolomic and transcriptomic technologies. BMC Plant Biology. https://doi.org/10.1186/s12870-026-10145-0

Image Credits: AI Generated

DOI: 10.1186/s12870-026-10145-0

Keywords: pumpkin leaves, foliar feeding, metabolomics, transcriptomics, 2-acetyl-1-pyrroline, putrescine, glutamic acid, umami, aroma biosynthesis, phytohormones, flavour chemistry, Cucurbita moschata

The research team, led by Jun Xu, Peng Shu and Zhe Wang across institutions in Xi’an, Ningbo, Hefei and Anhui, began with a straightforward but technically demanding question. What actually differs, metabolically, between myeloma cells that respond to bortezomib and those that do not? They sorted CD138-positive malignant plasma cells from the bone marrow of five bortezomib-resistant and five bortezomib-sensitive patients at their institution and ran untargeted metabolomics by liquid chromatography with tandem mass spectrometry. Among the features that separated the two groups was a compound annotated as N,N’-diferuloylputrescine, a derivative in which both amino groups of putrescine are capped with feruloyl groups. That fingerprint pointed the investigators toward the polyamine family, a set of positively charged molecules long known to stabilize nucleic acids and support rapid growth.

Polyamines, which include putrescine, spermidine and spermine, are classic metabolic workhorses. Cells can either manufacture them from ornithine through the ornithine decarboxylase pathway or import them from their surroundings through an assortment of poorly characterized transporters. The team tested both routes. When they incubated sorted patient cells with deuterium-labeled spermine and spermidine and measured intracellular accumulation by mass spectrometry, resistant cells took up more polyamine from outside. Meanwhile, quantitative PCR of the genes governing polyamine biosynthesis, interconversion and transport showed that the synthetic machinery was not obviously cranked up in resistant samples. Blocking biosynthesis with difluoromethylornithine, a well-studied inhibitor of ornithine decarboxylase, did not meaningfully reshape the bortezomib dose-response relationship in the way an uptake-dependent mechanism would predict. The message was clear: resistant myeloma cells were not making more putrescine, they were importing it.

The transporter responsible turned out to be SLC45A4, a member of the solute carrier family 45 that had not previously held a starring role in myeloma biology. SLC45A4 messenger RNA was upregulated in bone marrow samples from bortezomib-resistant patients compared with sensitive ones, and in public datasets such as GSE4581 and GSE2658, higher SLC45A4 expression in pretreatment CD138-selected plasma cells correlated with worse overall survival in patients treated within the University of Arkansas Total Therapy programs. When the researchers forced SLC45A4 overexpression in four myeloma cell lines, XG-7, RPMI8226, U266 and MM1.S, the cells became markedly more tolerant of bortezomib across apoptosis assays, proliferation assays and dose-response curves. Conversely, knocking SLC45A4 down in KMS-11 cells with short hairpin RNA sensitized them to the drug, and rescuing the knockdown restored the resistant phenotype, a classic demonstration that the transporter is functionally required rather than merely correlated.

Isotope tracing then confirmed what the transporter was carrying. Cells overexpressing SLC45A4 accumulated significantly more deuterium-labeled putrescine from the medium, while their uptake of labeled spermine and spermidine and their intracellular pools of those larger polyamines were comparatively unaffected. The specificity matters because it distinguishes SLC45A4 as a putrescine importer rather than a general polyamine conduit. The team also noted that culturing cells in heat-treated fetal bovine serum, which would degrade labile extracellular factors, blunted the survival advantage, hinting that the relevant putrescine supply is found outside the cell, in the tumor’s microenvironment, rather than being generated internally.

Having established the import route, the investigators asked what the imported putrescine actually does inside the cell. This is where the study becomes genuinely novel. Using putrescine immunoprecipitation followed by mass spectrometry of the bound proteins, they found that the homeobox transcription factor HOXA1 was enriched in the putrescine-associated fraction, and that this association increased when SLC45A4 was overexpressed. Structural modeling with AlphaFold 3 placed putrescine in close proximity to residues F277 and Q278 of HOXA1. A Q278E point mutation, designed to disrupt that contact without globally misfolding the protein, selectively impaired putrescine binding while preserving HOXA1’s intrinsic transcriptional competence toward representative target genes such as POLR2I, HEBP1 and INCA1. Cellular thermal shift assays supported the idea that putrescine engagement changes HOXA1’s thermal stability inside cells, and this engagement persisted even when the crosslinking enzyme TGM2 was inhibited or replaced with a catalytically inactive mutant, arguing against an indirect TGM2-dependent explanation.

Functionally, putrescine-bound HOXA1 behaved as an amplifier of NF-kappaB signaling, a pathway with obvious relevance to myeloma survival and drug resistance. RNA sequencing of HOXA1-overexpressing cells showed enrichment of NF-kappaB-related genes, and dual-luciferase reporter assays demonstrated that HOXA1 boosted NF-kappaB-driven transcription in response to upstream activators such as MYD88 and TRAF6. Disrupting putrescine binding with the Q278E mutation, or depleting HOXA1 with guide RNA, dampened that activation. Western blotting showed corresponding changes in phosphorylated p65 and I-kappaB-alpha. In the clinical APEX dataset of relapsed myeloma patients treated with bortezomib or dexamethasone, higher HOXA1 expression tracked with poorer overall survival, and crossed perturbation experiments in which SLC45A4 and HOXA1 were manipulated individually and in combination confirmed that the two act cooperatively to drive putrescine accumulation and bortezomib resistance.

Perhaps the most striking finding concerns where the putrescine comes from. Single-cell RNA sequencing of bone marrow from a healthy donor, a bortezomib-sensitive patient and a bortezomib-resistant patient, supplemented by an independent public dataset, GSE189460, pointed to myeloid-derived suppressor cells, or MDSCs, as a rich source of polyamine uptake and synthesis activity within the resistant niche. Co-culture tracing experiments suggested that myeloma cells acquire putrescine from these immune suppressor cells, and exploratory cell-cell communication analysis hinted at intensified crosstalk in the resistant marrow. The authors are appropriately careful here: with only one individual per condition in the discovery cohort, those single-cell analyses are explicitly descriptive and hypothesis-generating, while the patient-level validation in the independent cohort treated each patient as a single biological replicate. Even with that caution, the picture that emerges is of a tumor ecosystem in which immunosuppressive myeloid cells feed malignant plasma cells a small molecule that hardens them against chemotherapy.

The translational payoff came from a pharmacological screen. Abiraterone acetate, a drug already approved for prostate cancer as a CYP17A1 inhibitor, preferentially suppressed myeloma cells overexpressing both SLC45A4 and HOXA1. Treatment with the compound reduced putrescine uptake of N15-labeled spermidine and spermine, destabilized SLC45A4 messenger RNA in an actinomycin D chase assay, and appeared to act independently of CYP17A1, since CYP17A1 knockdown did not reproduce the SLC45A4 downregulation. Combining abiraterone acetate with HXR9, a peptide inhibitor of HOX-PBX transcriptional complexes, attenuated the resistance-associated phenotype, and triple combinations with bortezomib produced the strongest effects in viability and proliferation assays. Genetic knockdown and rescue experiments confirmed that abiraterone acetate sensitivity genuinely depends on SLC45A4 and HOXA1 rather than on an off-target artifact.

The study carries the usual caveats of early translational work: the patient metabolomics cohorts are small, the single-cell discovery sample is n of one per condition, and abiraterone acetate’s repurposing would require formal clinical testing in myeloma before anyone could prescribe it for this purpose. But the conceptual contribution is substantial. Bortezomib resistance, the authors argue, is not purely a cell-autonomous property of the malignant clone; it is a niche-dependent metabolic negotiation, in which SLC45A4 imports putrescine supplied by MDSCs, putrescine engages HOXA1 at a defined molecular interface, and the resulting complex amplifies NF-kappaB signaling enough to blunt a proteasome inhibitor’s lethal pressure. If that axis holds up in larger cohorts, it suggests a genuinely new class of intervention for relapsed myeloma: not attacking the cancer cell’s genome or its proteasome, but cutting the metabolic supply lines that the bone marrow itself has laid down.

Subject of Research: SLC45A4-mediated putrescine uptake driving HOXA1 and NF-kappaB signaling in bortezomib-resistant multiple myeloma

Article Title: SLC45A4-mediated putrescine uptake functionally modulates HOXA1 and promotes bortezomib resistance in multiple myeloma

Article References: Xu, J., Shu, P., Zhang, L., Li, H., Xu, Z., Meng, B., Ma, J., Wang, W., Wang, W., Wu, X., & Wang, Z. (2026). SLC45A4-mediated putrescine uptake functionally modulates HOXA1 and promotes bortezomib resistance in multiple myeloma. Journal of Experimental & Clinical Cancer Research. https://doi.org/10.1186/s13046-026-03843-y

Image Credits: AI Generated

DOI: 10.1186/s13046-026-03843-y

Keywords: multiple myeloma, bortezomib resistance, SLC45A4, putrescine, HOXA1, NF-kappaB, polyamine metabolism, myeloid-derived suppressor cells, bone marrow niche, abiraterone acetate, drug resistance, cancer metabolism

The research, carried out by Keyvan Pourrashid, Zohreh Jabbarzadeh, and Jafar Amiri at the Department of Horticultural Science, Faculty of Agriculture, Urmia University in Iran, was designed as a factorial experiment under a completely randomized design. The team foliar-applied silica dioxide nanoparticles at four concentrations: 0, 50, 100, and 200 milligrams per liter. These were crossed with three putrescine concentrations: 0, 1.5, and 3 millimolar. That twelve-treatment matrix allowed the researchers to separate the effects of each compound individually from the interactive effects of applying them in combination, a distinction that matters because biostimulants frequently behave differently in mixtures than they do on their own.

Silica nanoparticles have attracted growing attention in plant science over the past decade. Silicon is not classified as an essential element for most plants, yet abundant evidence shows that it strengthens cell walls, improves mechanical stability, and helps plants cope with environmental stress. Shrinking silicon down to the nanoscale changes the game further: nanoparticles offer an enormous surface-area-to-volume ratio, can adhere to and penetrate leaf surfaces more effectively than bulk particles, and may release silicon in a form that plant tissues can readily use. Previous work has shown benefits in crops as varied as sorghum under drought, maize under deficit irrigation, and ornamentals including roses, gerbera, carnation, and marigold, where silicon sprays have been linked to longer flowering periods and better postharvest performance.

Putrescine belongs to an entirely different family of molecules. It is a polyamine, a class of small nitrogen-rich compounds that participate in a startling range of plant processes, from cell division and DNA stabilization to flowering, fruit development, and responses to heat, salt, and drought stress. Polyamines carry positive charges that let them bind to negatively charged molecules such as DNA, RNA, and membrane phospholipids, which is one reason they help stabilize cellular structures under stress. They also crosstalk with major plant hormones, modulating the actions of auxins, gibberellins, and abscisic acid. Exogenous putrescine sprays have previously improved chlorophyll metabolism in tomato seedlings, salt tolerance in zinnia flowers, and postharvest quality in gerbera and alstroemeria cut flowers.

The rationale for combining the two was straightforward: silica nanoparticles and putrescine support plant performance through largely independent mechanisms, so their effects might add up or even multiply. What was missing, the authors note, was any systematic information about how the two interact in stock, an economically important ornamental whose commercial value depends almost entirely on vegetative vigor, floral quality, and vase life. The new experiment fills that gap with a full factorial design, meaning every nanoparticle concentration was tested against every putrescine concentration, including untreated controls for both.

The results were unambiguous in their overall direction. Compared with untreated plants, foliar application of silica nanoparticles and putrescine, particularly at appropriate concentrations and in combination, improved vegetative growth, biomass accumulation, floral quality, and vase life. But the standout treatment was not the highest dose of either compound. The best performance across most evaluated traits came from combining 1.5 millimolar putrescine with just 50 milligrams per liter of silica nanoparticles, the lowest nanoparticle concentration tested. That finding carries a practical message: in biostimulant science, more is not always better, and moderate doses can outperform aggressive ones, both in terms of plant response and in terms of cost and environmental loading.

The biochemical data help explain why the winning combination worked. Plants receiving the optimal treatment showed increased contents of chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids, the pigment suite that drives photosynthesis. More chlorophyll means greater capacity to capture light energy and fix carbon, which in turn supports the vegetative growth and biomass gains the researchers recorded. Carotenoids do double duty as accessory pigments and as antioxidants that quench reactive oxygen species generated during photosynthesis, so their elevation suggests the treated plants were not only photosynthesizing more but also protecting their photosynthetic machinery more effectively.

The treatment also raised levels of soluble sugars, proteins, and anthocyanins. Soluble sugars are the currency of plant metabolism and a critical determinant of cut flower longevity, since a detached flower survives largely on the carbohydrate reserves it carried at harvest. Higher sugar content at the moment of cutting translates directly into more fuel for respiration and petal maintenance in the vase. Elevated protein content points to a more active metabolic state, while increased anthocyanins, the pigments responsible for red, purple, and blue coloration in plant tissues, indicate enhanced secondary metabolism and potentially better visual quality and stress resilience. Taken together, the biochemical profile suggests that the combined treatment improved the photosynthetic capacity and overall metabolic status of the plants before harvest, setting them up for a longer postharvest life.

The interactive nature of the effect is arguably the study’s most interesting scientific contribution. In a factorial design, an interaction means the response to one factor depends on the level of the other. Here, the fact that the best outcome came from a specific pairing rather than from either compound alone indicates genuine synergy or at least complementary action. One plausible mechanistic picture is that silica nanoparticles reinforce the physical infrastructure of leaves and stems while putrescine tunes the biochemical and hormonal environment inside cells, with the two effects converging on the same outcome: plants that grow better, flower better, and hold up longer after cutting. The authors suggest that this interactive strategy may represent a promising biostimulant approach for enhancing the commercial quality of ornamental plants more broadly.

For the floriculture industry, the implications are tangible. Stock is grown in greenhouses under tight schedules, and every extra day of vase life adds value for wholesalers, retailers, and consumers alike. A foliar spray protocol that combines a low dose of silica nanoparticles with a moderate dose of putrescine could, if validated at commercial scale, offer growers a relatively simple preharvest intervention to raise quality without genetic modification or heavy pesticide use. The study also adds to a fast-growing literature on silicon-based nanomaterials in sustainable agriculture, where researchers are exploring everything from nanoparticle uptake and translocation pathways to their roles in stress mitigation and nutrient management. Questions certainly remain, including how the treatment performs across different stock genotypes, seasons, and growing systems, and what the long-term environmental fate of engineered silica particles in greenhouse operations might be. But the core finding stands: two well-studied biostimulants, applied together at the right doses, can measurably improve how a flower grows, how it looks, and how long it lasts in the vase, and that combination may soon find a place in the greenhouse toolkit.

Subject of Research: Interactive effects of foliar-applied silica nanoparticles and putrescine on growth, biochemistry, and vase life of stock (Matthiola incana)

Article Title: Interactive effects of silica nanoparticles and putrescine on morphophysiological and biochemical performance in stock (Matthiola incana L. ‘Pilaster White’)

Article References: Pourrashid, K., Jabbarzadeh, Z., & Amiri, J. (2026). Interactive effects of silica nanoparticles and putrescine on morphophysiological and biochemical performance in stock (Matthiola incana L. ‘Pilaster White’). The Science of Nature, 113(6), Article 123. https://doi.org/10.1007/s00114-026-02177-1

Image Credits: AI Generated

DOI: 10.1007/s00114-026-02177-1

Keywords: silica nanoparticles, putrescine, stock, Matthiola incana, ornamental horticulture, vase life, chlorophyll, biostimulants, floriculture, plant physiology, nanotechnology, greenhouse production