Plant Physiology最新文献

Low temperature limits the productivity and quality of tea plants, particularly when spring cold spells damage vulnerable young shoots. However, the metabolic signals that regulate C-repeat binding factor (CBF)-mediated cold responses remain unclear. Time-series metabolomic analysis revealed progressive glutamate accumulation in cold-treated tea shoots, accompanied by a marked decline in theanine content. Exogenous glutamate enhanced cold tolerance in tea shoots. By contrast, co-silencing of CsGGT2 and CsGGT4 attenuated cold-induced glutamate accumulation and compromised cold tolerance, indicating that CsGGT2/CsGGT4-associated theanine turnover contributes to cold-induced glutamate accumulation. Silencing CsGLR3.2 attenuated the protective effect of glutamate and reduced glutamate-enhanced CsCBF1-CsCBF4 expression. Pharmacological treatments provided complementary support for the involvement of GLR- and Ca2+-associated signaling in this response. Transcriptomic analysis further showed that glutamate altered the expression of genes associated with flavonoid biosynthesis and redox homeostasis. Collectively, these findings connect the characteristic theanine metabolism of tea plants with cold-responsive glutamate signaling and support a model in which glutamate enhances CsCBF expression through CsGLR3.2- and Ca2+-associated signaling. Glutamate metabolism and GLR-associated signaling therefore represent potential targets for improving cold tolerance in tea plants.

Seed dormancy is a key strategy for plants to adapt to fluctuating environments and ensure population propagation. Paeonia lactiflora seeds exhibit typical double dormancy, characterized by a prolonged germination cycle and low emergence rate that severely restrict their large-scale propagation. Although ABI5, the core transcription factor (TF) in the abscisic acid (ABA) signaling pathway, acts as a critical hub in maintaining seed dormancy, its upstream dynamic regulatory mechanism and downstream cell-wall-related target genes remain largely unknown. In this study, two upstream regulators of PlABI5, PlMYB51 and PlMYB1R1, were identified via yeast one-hybrid screening, and their regulatory mechanism was characterized. The results showed that both PlMYB51 and PlMYB1R1 belonged to the R2R3-MYB family. When acting alone, they directly bound to and activated the PlABI5 promoter, inhibiting seed germination. Upon forming a protein complex in the nucleus, their regulatory function was reversed and they repressed PlABI5 transcription to promote germination, supporting a proposed monomer activation-complex inhibition switch model. Furthermore, PlABI5 specifically targeted the PlCesA6 promoter and inhibited its expression without affecting the homolog PlCesA3. PlCesA6 positively regulated seed germination by promoting hypocotyl cell elongation, and its overexpression rescued the inhibition caused by PlMYB51/PlMYB1R1 overexpression. Collectively, this study proposes a working model for the PlMYB51/PlMYB1R1-PlABI5-PlCesA6 cascade in controlling seed dormancy and germination, and identifies a putative functional switching mode of MYB TFs mediated by protein-protein interactions. These findings provide key gene resources and a theoretical basis for artificial dormancy breaking and molecular breeding in P. lactiflora.

Plant chitinases are important defense enzymes in plant-microbe interactions and also participate in nodule symbiosis between legumes and nitrogen-fixing rhizobia. However, the roles of chitinases in arbuscular mycorrhizal (AM) symbiosis remain incompletely defined. In this study, we characterized two class III chitinase genes in the legume Medicago truncatula (ecotype R108), namely MtCHIT3e and MtCHIT3f. Heterologous expression in Nicotiana benthamiana confirmed hydrolytic activity toward colloidal chitin, a fluorogenic chitooligosaccharide substrate, chitooligosaccharides, and lipo-chitooligosaccharides. In M. truncatula roots inoculated with AM fungi, transcripts of the two genes were significantly upregulated. Analysis of M. truncatula hairy roots transformed with promoter-β-glucuronidase constructs indicated strong induction of MtCHIT3e and MtCHIT3f promoter activity in response to applied chitooligosaccharide and lipo-chitooligosaccharide signals. Furthermore, fluorescent protein fusions localized the chitinases predominantly to the apoplast of host cells during AM colonization. Tnt1 insertion mutants in the chitinase genes exhibited reduced AM colonization, whereas nodule formation induced by Sinorhizobium meliloti was unaffected. Together, these results support a role for class III chitinases in promoting AM symbiosis and provide genetic evidence that they are required for optimal root colonization by AM fungi.

Heat stress has become a primary environmental factor that severely threatens crop yield and quality. Despite many genes having been identified to participate in heat response, natural alleles of heat response genes that can be utilized in crop breeding are scarce, and the underlying mechanisms remain enigmatic. In this study, we identified a BEL1-like Homeodomain (BLH) transcription factor CsBLH9, through genome-wide association study (GWAS), and demonstrated its positive role in heat response. The natural variants of CsBLH9 exhibit different levels of heat tolerance and differential response to gibberellin (GA) treatment. Knockout of CsBLH9 resulted in sensitive heat response and reduced chlorophyll levels. CsBLH9 can directly bind to the promoters of chlorophyll catabolic genes stay-green (CsSGR) and pheophorbide a oxygenase (CsPAO) to inhibit their expression. Furthermore, we identified CsOVATE as an interacting partner of CsBLH9 that also functions as a positive regulator of heat tolerance. Csovate mutants showed phenotypes similar to Csblh9 mutants under heat stress, and CsOVATE enhanced the CsBLH9-mediated inhibition of CsSGR and CsPAO expression. Therefore, our findings suggested that CsBLH9-CsOVATE acts as a module that regulates heat tolerance via chlorophyll degradation in cucumber, and the natural alleles of CsBLH9 provide new targets for crop improvement under heat stress.

Ubiquitination is an essential post-translation modification involved in almost every cellular process and is critical for proper functioning of eukaryotic cells. The modification involves the covalent attachment of ubiquitin, a small, conserved peptide, to select proteins. One or more ubiquitin molecules may be attached in varying configurations, leading to a range of possible outcomes that regulate protein function, including changes in location, stability, and activity. Components of the ubiquitin system are highly expanded in plants relative to other eukaryotes and play major roles in almost all aspects of plant growth and development, from phytohormone perception and signalling, to maintaining nutrient homeostasis in the face of fluctuating environmental conditions. We begin this Centennial Review by highlighting two Plant Physiology papers that contributed to the identification and characterisation of ubiquitin enzymes. We then provide an update on our understanding of how plants use the ubiquitin system to link environmental change with plant growth and development. We first focus on recent advances in understanding how the structure and function of ubiquitin ligases are modulated by phytohormones and nutrient status. We then highlight emerging knowledge linking components of the ubiquitin system with biomolecular condensates, including stress granules, and discuss the potential functional implications.

Strigolactones (SLs) and Karrikins (KARs) are butenolide compounds that have been characterized to act like phytohormones. While SLs are synthesized endogenously in plants from carotenoids, KARs are a known constituent of wildfire smoke emanating from the combustion of carbohydrates in burning plant tissues. Despite their different sources of origin, they have similar chemical structures and are perceived through similar receptor complexes. However, the compound-specific molecular pathways downstream of these two signalling molecules remains to be elucidated. Hereby, we adopt an integrated approach combining transcriptome, proteome, proteogenome and metabolome profiling to compare the molecular responses of seeds and seedlings to the synthetic strigolactone analog, rac-GR24 and to the karrikinolide, KAR1 in Arabidopsis seeds or seedlings. This multi-omics approach allowed us to delineate the key conserved, and compound-specific, regulators such as transcription factors, splicing-related proteins, and primary metabolites that could play important functional roles in establishing the signaling response to these butenolides. Correlational analysis suggested differential splicing and metabolite regulation in response to rac-GR24 and KARs suggesting potential molecular targets including the TCA cycle. Treatment of mutants of key enzymes of energy metabolism, identified in the above studies, revealed that these mutants showed altered metabolic responses to butenolide treatment. In summary, our integrative dataset reveals strong associations between butenolide treatment and TCA cycle related changes across multiple molecular levels, and provides a foundation for generating testable hypotheses on how these signals interface with energy metabolism.

Beneficial Trichoderma fungi enhance plant immunity, but the molecular mechanisms of elicitor-mediated immune priming are still not well defined. Here, we identified a cerato-platanin (CP) family elicitor, CP3, from T. asperellum that enhances tomato resistance to Botrytis cinerea. CP3 is secreted and localizes to the host nucleus, where it interacts with the tomato protein SRP. This interaction recruits casein kinase 1 to phosphorylate SRP at Ser-185, thereby triggering its nuclear export to the plasma membrane. Subsequently, SRP binds the ubiquinone biosynthesis protein COQ9, forming a signaling module that activates reactive oxygen species production and jasmonate/ethylene defense pathways to establish induced systemic resistance. Genetic disruption of CP3, SRP, or COQ9 abolishes CP3-induced resistance, confirming their essential roles. Our findings reveal a complete CP3-SRP-COQ9 signaling axis through which a beneficial fungal elicitor reprograms host nucleocytoplasmic trafficking to activate tailored immunity, offering new molecular targets for engineering disease-resistant crops.

Drought stress severely constrains tomato productivity, yet the transcriptional circuitry governing drought adaptation remains incompletely understood. Here, we demonstrate that SlNF-YC9 assembles with SlNF-YB3b and SlNF-YA3a into a functional NF-Y heterotrimer that enhances drought tolerance. This complex promotes stomatal closure, limits reactive oxygen species accumulation, and elevates abscisic acid levels. Mechanistically, the NF-Y trimer directly activates the drought-responsive genes SlAREB1 and SlDREB2 by binding the CCAAT motif, with SlNF-YA3a mediating DNA contact and the intact complex conferring maximal transcriptional activation. Notably, this activity is antagonized by SlWRKY16, which physically interacts with SlNF-YC9 and suppresses NF-Y-dependent transcription. Genetic analyses further support the cooperative function of SlNF-YC9 and SlNF-YB3b, as well as the antagonistic role of SlWRKY16, in regulating drought tolerance. Together, our findings define the NF-Y complex as a key regulatory component that coordinates positive and negative transcriptional inputs during the tomato drought response, providing a molecular framework for targeted crop improvement.

Nitrogen assimilation plays a crucial role in plant growth and protein accumulation. Urea is a widely used and low-cost nitrogen source; therefore, efficient assimilation of urea-derived nitrogen is critical for biomass accumulation and protein production in plants. However, the regulatory factors that enhance this process remain poorly understood. Here, we identify the chloroplast-localized ACT DOMAIN REPEAT 11 (ACR11) as a positive regulator of nitrogen assimilation in duckweed. Overexpression of LpACR11 increased growth rate, protein content and protein productivity of duckweed Lemna minor ZH0403 under urea nutrition, whereas RNAi-mediated knockdown caused opposite effects. Heterologous expression of LpACR11 in tobacco and rice also enhanced biomass and protein accumulation under urea cultivation conditions. Biochemical and metabolic analyses showed that LpACR11 overexpression was associated with increased Fd-GOGAT (ferredoxin-dependent glutamate synthase) activity, elevated glutamate accumulation, reduced ammonium accumulation and increased total amino acid content. Glutamate treatment further promoted GS2 (plastid glutamine synthetase) expression and activity, supporting a working model in which ACR11-associated enhancement of Fd-GOGAT activity increases glutamate accumulation and thereby promotes GS2-associated nitrogen assimilation. Together, these results indicate that ACR11 enhances chloroplast nitrogen-assimilation capacity and protein productivity during urea cultivation, providing a potential genetic target for improving protein productivity in duckweed and other crops.