VyMYB258, A MYB Transcription Factor From Vitis yanshanensis, Enhances Drought Tolerance by Activating the Lignin Biosynthesis Pathway.

Drought stress is a major environmental constraint that limits global agricultural production and sustainable development of agriculture. MYB transcription factors constitute a large gene family in plants, with many members involved in drought stress regulation. However, the mechanisms by which drought-activated MYB transcription factors regulate metabolic pathways such as lignin biosynthesis to confer drought tolerance in grapevine remain poorly understood. In this study, the MYB transcription factor VyMYB258 was identified from Vitis yanshanensis and found to mediate the lignin biosynthesis pathway, thereby enhancing drought tolerance in grapevine. VyMYB258 is a nuclear-localized protein with transcriptional activation capability. VyMYB258 transcripts were quickly induced by drought stress and were particularly abundant in grape roots and leaves. Heterologous overexpression of VyMYB258 in tomato significantly enhanced drought tolerance. Under drought conditions, transgenic lines showed markedly less leaf wilting, reduced water loss, and lower electrolyte leakage compared to the control tomato plants. Notably, drought treatment markedly boosted the transcript levels of core genes involved in lignin formation within grapevine tissues. Further experiments revealed that VyMYB258 could bind directly to the promoters of key lignin biosynthetic enzymes (VyPAL2, VyPAL4, Vy4CL2, and VyCAD4), activating their expression and thereby promoting lignin biosynthesis and deposition. In summary, this study systematically elucidates the molecular pathway through which VyMYB258 enhances plant drought tolerance by promoting lignin accumulation. Our results deepen the knowledge of MYB-mediated drought adaptation in grapevine and offer both valuable gene resources and a conceptual basis for developing stress-resilient grape cultivars.