生命科学最新文献

Hydroxycinnamoyl tyramine conjugates are phenolamides produced by plants in response to pathogen attack and biotic stresses. Their proposed mechanisms of action include cytotoxicity towards pathogens, cell wall reinforcement to restrict pathogen proliferation, and signaling activity to trigger general stress responses. Here, we engineered the production of the tyramine conjugates p-coumaroyltyramine (CT) and feruloyltyramine (FT) in Arabidopsis to gain insight into their mode of action. Co-expression of feedback-insensitive 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase and tyrosine decarboxylase increased tyramine content. Additional expression of tyramine hydroxycinnamoyltransferase led to de-novo production of CT and FT, which were found as soluble and cell-wall-bound forms. FT was associated with lignin in stems. The growth of pathogenic Pseudomonas syringae was reduced in rosettes of the Arabidopsis CT- and FT-producing lines compared to wild type. These lines also exhibited increased transpirational water loss in excised rosettes. Transcriptomic analysis of transgenic lines grown under normal conditions revealed alterations in the expression of genes associated with the biological circadian clock. These changes led to a reduction in flavonoids and an early flowering phenotype. Important changes in the expression of genes related to abiotic stress such as drought, cold, heat, and hypoxia potentially contribute to reduced growth of P. syringae in engineered Arabidopsis.

Upon attack by insect herbivores, plants can perceive herbivore-derived physical and chemical cues and rapidly reallocate their resources for growth and defense. Insect herbivory specifically induces rapid systemic down-regulation of plant photosynthesis, characterized by whole-plant systemic stomatal closure. However, its underlying mechanism is not fully understood. Here, we found that the simulated herbivory (wounding + oral secretion, WOS) in tomato local (treated) leaflets triggered a decrease of more than 45.0% in stomatal conductance (g_s) in the systemic (adjacent and distal) uninjured leaflets 3 h after the treatment. Local WOS treatment also induced local upregulation of jasmonic acid (JA) biosynthesis genes and systemic JA accumulation in wild-type tomato. Consistently, the systemic stomatal closure response was severely compromised in JA synthesis-deficient mutants (spr2 and spr8). Grafting experiments with wild-type and spr8 mutant proved that the local JA biosynthesis triggered by WOS is essential for systemic stomatal closure. In addition, JA-mediated H₂O₂ bursts in the systemic guard cells is vital for systemic stomatal closure triggered by local WOS treatment. Our findings reveal a crucial role of local JA biosynthesis and systemic JA-mediated H₂O₂ bursts in systemic stomatal responses triggered by insect herbivory in tomato.

Developing drought-resilient crops requires a precise understanding of molecular signalling in the root, the primary organ encountering drought. This study unravelled novel genetic loci regulating drought tolerance by exploiting the natural variation in seedling root growth of Arabidopsis thaliana under PEG-induced drought stress. Through a genome-wide association study of 207 worldwide A. thaliana ecotypes from regions with varied rainfall, 68 protein-coding genes were identified with the top 50 SNPs. Functional enrichment and network analyses demarcated key processes involved in stress tolerance, including DNA repair, tRNA editing, protein folding, cell cycle regulation, stress granule assembly and the pyridoxal 5'-phosphate (PLP) salvage pathway. Expression level polymorphisms, promoter cis-element variations and amino acid substitutions associated with phenotype and climate were identified. Reverse genetic evaluation using T-DNA insertion knockout/knockdown mutants confirmed the involvement of candidate genes: AT1G06690 (PLP pathway), AT4G26990, RBP45C (stress granules), ACD55.5 (protein folding), PCMP-A4 (AT1G14470; RNA editing), SKS6, ANAC094 (cell wall remodelling) and INCENP (cell cycle), with seedling drought tolerance. Specifically, knockdown of AT1G06690 resulted in higher root hydrogen peroxide accumulation, highlighting the importance of the PLP pathway in mitigating oxidative stress. These molecular insights offer new biotechnological and breeding tools to enhance crop drought tolerance by modulating root traits.

Lipid remodelling is a fundamental component of plant responses to environmental stress and development, yet its regulation in fast-growing aquatic plants remains poorly understood. Here, we investigated how abscisic acid (ABA) regulates triacylglycerol (TAG) accumulation and fatty acid (FA) composition in the duckweed Lemna minor. A 3-day treatment with 1 µM ABA induced a 2.9-fold increase in TAG content, accompanied by extensive remodelling of plastidial and extraplastidial membrane lipids. Reduced monogalactosyldiacylglycerol (MGDG) likely served as a FA source for TAG synthesis. Transcript analyses revealed strong induction of diacylglycerol acyltransferase (DGAT) genes, catalysing the final step of TAG formation, and repression of fatty acid desaturase (FAD) genes, resulting in a marked reduction in polyunsaturated FA levels. Confocal imaging confirmed substantial lipid droplet accumulation in both fronds and chloroplast-containing roots. Notably, this sustained ABA-induced TAG accumulation was unique to L. minor, with no comparable response observed in other duckweed species or in Arabidopsis under identical treatment. These findings reveal a species-specific ABA-driven lipid remodelling pathway in duckweed, linking phytohormone signalling to carbon storage in aquatic plants.