Plant Physiology and Biochemistry最新文献

The dehydration-responsive element binding (DREB) subfamily, belonging to the APETALA2/ethylene-responsive element binding (AP2/ERF) superfamily, is crucial for plant growth and development. Despite the identification of DREB genes in numerous plant species, research on the DREB2 family in alfalfa remains incomplete. In this study, we used the alfalfa cultivar "Zhongmu No. 4" to identify and characterize 11 MsDREB2 genes through whole-genome analysis. These genes were unevenly distributed on chromosomes 1 and 2 and on unanchored scaffold chromosomes. A phylogenetic analysis involving Arabidopsis thaliana, Medicago truncatula, and Medicago sativa showed that MsDREB2 members were divided into four clades. Synteny analysis revealed that 45.5% (5 out of 11) of MsDREB2 genes formed segmental duplications, with no tandem duplications observed. The Ka/Ks analysis indicated that some gene pairs underwent purifying and positive selection. Cis-acting elements involved in plant growth, hormone responses, and stress responses were found in the promoters of the MsDREB2 genes. MsDREB2-04 exhibited variable responses to salt and drought stress, determined by qRT-PCR. Under drought stress, the Arabidopsis thaliana dreb2d mutant showed markedly reduced growth. In contrast, MsDREB2-04 overexpression in alfalfa enhanced drought tolerance. Conversely, VIGS silencing of MsDREB2-04 reduced drought tolerance. This study provides a comprehensive identification of the MsDREB2 gene family in alfalfa and confirms the role of MsDREB2-04 in drought stress responses. These findings provide a foundation for functional studies of MsDREB2 genes.

Exposure to indium oxide nanoparticles (In₂O₃-NPs) presents a critical challenge as an emerging soil contaminant that severely impairs plant growth and metabolic health. In this study, In2O3-NP exposure reduced biomass by 58% in alfalfa, driven by excessive indium (In) accumulation, disrupted mineral (P and Fe) balance, and inhibited photosynthesis. This physiological decline led to a significant depletion of sugars and nitrogen metabolites, particularly in the more sensitive alfalfa model. To mitigate these toxic effects, we utilized cyanobacterial priming (CP) with Anabaena laxa to investigate how species-specific metabolic and physiological responses are shaped in alfalfa (legume) and rye (grass). CP treatment differentially mitigated toxicity by reducing In uptake, maintaining nutrient homeostasis, and restoring photosynthetic efficiency. This resulted in improved biomass, with alfalfa showing the most significant recovery. Mechanistically, CP enhanced sugar and nitrogen metabolism, providing the necessary precursors for the accumulation of protective secondary metabolites, such as phenolics and flavonoids, which reduced oxidative damage. Furthermore, CP induced a structural adaptation through the activation of the phenylpropanoid-lignin biosynthetic pathway. In alfalfa, elevated levels of cinnamic and coumaric acids were linked to increased activities of key enzymes, phenylalanine ammonia-lyase (PAL), caffeic acid O-methyltransferase (COMT), cinnamyl alcohol dehydrogenase (CAD), and cinnamoyl-CoA reductase (CCR). This resulted in a substantial 243.6% increase in lignin in alfalfa, compared to a 115.1% rise in rye. This study demonstrates that while rye relies on inherent physiological tolerance, alfalfa exhibits superior metabolic plasticity when primed with CP. These findings prove that alfalfa and rye utilize distinct survival strategies at the biochemical level; while rye leverages its natural resilience, alfalfa undergoes a complete metabolic reorganization to rescue its growth and survive nanoparticle stress.

Sugar content is among the most important agronomic traits in tomatoes. High-sugar tomatoes are usually produced by applying water stress, which results in a significant reduction in fruit yield. We developed a hydroponic method involving the use of coral sand as a solid medium and optimized a nutrient management protocol to produce high-sugar tomatoes while largely maintaining yield. In this study, we analyzed the mechanism by which coral sand increases sugar content. Transcriptome analysis revealed that the expression of phosphorus deficiency-inducible genes increased in the leaves of tomato plants grown on coral sand. The phosphate concentration in both the nutrient solution and leaves decreased when the plants were grown on the coral medium, suggesting that the response to mild low-phosphate conditions may be associated with the increase in sugar content. In addition, under mild low phosphate in hydroponic culture, the sugar content in the fruit increased, even though the fruit yield decreased. Interestingly, comparisons of gene expression levels under these conditions with those from previously reported mild drought experiments showed that homologs of genes that are induced by coral sand were also upregulated in response to mild drought. Collectively, our findings reveal a previously unrecognized ability of hydroponic cultivation using coral sand to create mild low-phosphate conditions that trigger sugar accumulation pathways associated with mild drought. This study not only provides a practical strategy for producing high-sugar tomatoes using a coral sand cultivation system with minimal impact on yield, but also suggests a role for low-phosphate responses in regulating sugar accumulation in fruits.

Drought stress occurs intermittently and severely constrains plant growth and production. Constitutive overexpression of stress-responsive genes can improve drought tolerance but often imposes unnecessary metabolic costs under favorable conditions. Stress-inducible promoters therefore represent an important regulatory resource for precision engineering of drought tolerance. In this study, a drought-inducible promoter from switchgrass (Panicum virgatum L.), PvHVA1pro, derived from the late embryogenesis abundant gene PvHVA1 (Hordeum vulgare aleurone 1) was identified and functionally validated. Transcript analysis showed that PvHVA1 expression is strongly induced by PEG-mediated osmotic stress, with minimal basal expression under non-stress conditions. Stable transgenic switchgrass expressing PvHVA1pro::GUS exhibited drought-dependent and reversible promoter activity in vegetative tissues. To demonstrate its practical utility, PvHVA1pro was used to drive the aquaporin gene PvPIP2;9 in switchgrass that the inducible expression of PvPIP2;9 enhanced drought tolerance, photosynthetic performance, and water-use efficiency compared with wild-type plants, without pronounced growth penalties. Together, these results establish PvHVA1pro as a sensitive, low-basal, drought-inducible promoter resource for switchgrass, providing an enabling regulatory tool for functional genomics and precision drought-tolerance engineering in bioenergy crops.

Cinnamomum camphora var. linaloolifera is a primary source of natural linalool, an acyclic monoterpene with high industrial value, yet the molecular basis of its high-purity accumulation remains poorly understood. In this study, we characterized 'Nan'an 1', an elite cultivar, identifying it as a unique chemotype with exceptional linalool purity (88.30%) and negligible metabolic byproducts via comparative metabolomics. Genome-wide analysis identified 46 CcTPS genes, revealing a significant expansion of the TPS-b subfamily. Notably, the TPS-g subfamily clustered closely with TPS-b but exhibited a specific loss of the cyclization-associated RRX8W motif. This structural divergence provides a theoretical basis for the functional specialization of TPS-g in acyclic monoterpene biosynthesis. Transcriptomic and qRT-PCR analyses revealed that the high expression of four TPS-g candidates (CcTPS14, CcTPS15, CcTPS16, and CcTPS32) significantly correlates with linalool accumulation. Furthermore, heterologous expression in Escherichia coli and in vitro enzymatic assays conclusively demonstrated that these four recombinant proteins function as highly specific linalool synthases, efficiently converting geranyl diphosphate (GPP) into linalool. These findings suggest that the TPS-g subfamily likely originated from the TPS-b lineage through the specific loss of the RRX8W domain, thereby specializing in linalool synthesis. This study elucidates the genetic and molecular mechanisms of high-purity linalool accumulation, offering precise target genes for metabolic engineering.

The basic helix-loop-helix (bHLH) transcription factors MYC2 and its paralogs are master regulators in jasmonate (JA) signaling in Arabidopsis, yet their functions in potato (Solanum tuberosum) remain poorly understood. Here, we identified and characterized StMYC1, a potato transcription factor that clusters phylogenetically with tomato SlMYC1 and contains conserved JASMONATE ZIM-DOMAIN (JAZ)-interacting and bHLH domains. Overexpression of StMYC1 in Arabidopsis recapitulated canonical JA-hyperresponsive phenotypes in plant development and defense responses, confirming its functional conservation in the JA signaling pathway. Yeast two-hybrid assays demonstrated that StMYC1 interacts with Arabidopsis JAZ repressors and potato StJAZ1-like, indicating its integration into the core JA signaling module. Transcriptome analysis revealed that StMYC1 reprograms the gene expression profile in Arabidopsis leaves to enhance defense-related gene expression while repressing genes associated with plant growth. Strikingly, overexpression of StMYC1 in potato conferred a dual beneficial effect, including increased microtuber yield under in vitro conditions and enhanced resistance to Spodoptera exigua. Physiological and molecular analyses showed that StMYC1 improves photosynthetic capacity in source leaves and upregulates the expression of genes involved in sucrose transport, starch biosynthesis, and tuberization in sink microtubers. Moreover, StMYC1 enhances the constitutive and inducible accumulation of steroidal glycoalkaloids (SGAs), as well as the inducible expression of JA-responsive defense genes, in potato leaves. Our work demonstrates that StMYC1 is a conserved JA signaling component that coordinately improves herbivore resistance and microtuber production in potato likely by enhancing source capacity and redirecting resource allocation to favor both tuber storage and leaf defense. These results highlight StMYC1 as a promising target for breeding potato varieties with enhanced herbivore resistance and tuber yield, and provide insights for the genetic improvement of other storage-organ crops.

Following harvest, the medicinal quality of Dendrobium officinale declines due to ongoing metabolism. This study applied sodium nitroprusside (SNP) treatment and used biochemical and transcriptomic analyses to investigate its effects. Results showed that 400 μmol L^-1 SNP increased soluble sugars, proteins, antioxidant capacity, and stress resistance. Transcriptomic analysis revealed upregulation of MAN, PFK, PFP, and GMD, correlating with a 163% increase in polysaccharides, while downregulation of ALDO, TREH, and ENPP reduced cellulose and starch. Upregulation of F3H, CHS, and HCT boosted flavonoids and polyphenols, and upregulation of MVK, PAL, COMT, 4CL, and CYP73A led to a 179% rise in dendrobine. Transcription factors ERF, MYB, and WRKY were also implicated. SNP treatment redirected carbon allocation from starch/cellulose to bioactive polysaccharides and promoted dendrobine and flavonoid accumulation, thereby enhancing medicinal quality. This study offers new strategies for maintaining postharvest quality in medicinal plants.

Schizonepeta tenuifolia is a medicinal plant whose bioactive monoterpenoids, such as pulegone, are biosynthesized and stored in peltate glandular trichomes. Although jasmonate signaling is known to promote trichome development and terpenoid accumulation, the underlying transcriptional regulators in S. tenuifolia remain unknown. Here, we identified two jasmonate-responsive MYC2-type transcription factors, StMYC2a and StMYC2b, which are predominantly expressed in leaves and localized to the nucleus. Overexpression of StMYC2a and StMYC2b in S. tenuifolia increased the peltate glandular trichome density and monoterpenoid content. Conversely, transgenically silenced StMYC2a and StMYC2b lines had attenuated peltate glandular trichome development and reduced monoterpenoid accumulation. We further demonstrated that StMYC2a and StMYC2b directly activate two key monoterpenoid biosynthetic genes, StL3OH and StPR, by binding to G-box motifs in their promoters. Protein interaction analysis reveals that only StMYC2b physically interacts with the repressor StJAZ2, which suppresses StMYC2b-mediated transactivation, but this repression was alleviated upon stimulation with methyl jasmonate. The results revealed that the StJAZ2-StMYC2b-StL3OH/StPR functional module regulates jasmonic acid signaling-mediated glandular trichome development and monoterpenoid synthesis in S. tenuifolia. The enrichment of the transcriptional regulatory network for monoterpenoid synthesis provides a new theoretical basis for producing S. tenuifolia with high medicinal value.

The escalating threat of cadmium (Cd) contamination in agricultural soils poses serious challenges to food security and necessitates sustainable mitigation strategies. This study evaluated the combined effects of plant growth-promoting rhizobacteria (PGPR) and earthworms (Eisenia fetida) on Cd accumulation and associated physiological responses in rice (Oryza sativa L.). A controlled pot experiment was conducted under greenhouse conditions using plants exposed to Cd stress (100 mg kg^-1 soil), representing a severe contamination scenario used to evaluate mitigation responses under high Cd stress, with the application of Serratia marcescens, Pseudomonas fluorescens, and earthworms, individually and in combination. The results indicated that combined inoculation with PGPR and earthworms enhanced plant growth, improved photosynthetic efficiency, stimulated antioxidant defenses, increased osmolyte accumulation, and modulated cell wall-associated biochemical components, contributing to reduced Cd accumulation in O. sativa tissues. Furthermore, improvements in nutrient uptake and regulation of stress-related biochemical processes were observed, supporting enhanced tolerance under Cd exposure. Health risk indices (hazard quotient and hazard index) were markedly reduced, reflecting lower Cd transfer to edible tissues. Protein fraction and ribosomal protein analyses indicated increased total soluble protein content, enhanced protease activity, and greater ribosomal protein yield under biological treatments. Overall, the combined application of PGPR and earthworm reduced Cd accumulation and supported physiological resilience under controlled greenhouse conditions however, field validation and long-term assessment are required before broader agronomic application can be inferred.