VyMYB24 Integrates Antioxidant Defense and Cold Acclimation Networks to Enhance Freezing Tolerance in Chinese Wild Grape Vitis yeshanensis ‘Yanshan’

Cold stress severely impairs grapevine (Vitis vinifera L.) growth, development, and productivity, necessitating the identification of elite cold-resistance genes for breeding tolerant cultivars. Chinese wild grape germplasm, particularly the endemic Vitis yeshanensis ‘Yanshan’ ecotype, represents a valuable reservoir of stress-resistance alleles with exceptional cold hardiness. In this study, we isolated an R2R3-MYB transcription factor gene VyMYB24 from ‘Yanshan’ grape and systematically characterized its function in low-temperature responses. VyMYB24 expression was rapidly and strongly induced by cold stress, with transcript levels peaking at 12 h after treatment. Heterologous overexpression of VyMYB24 in transgenic tobacco (Nicotiana benthamiana) induced pronounced architectural changes. Transgenic plants exhibited a dwarf and compact stature with enhanced lateral branching, thickened stems, and robust root systems. In addition, anatomical analysis revealed markedly increased xylem and phloem thickness. Under cold stress, transgenic lines outperformed wild-type plants, with reduced wilting, lower water loss, and improved survival and recovery rates. Physiologically, VyMYB24 activated the antioxidant defense system, elevated the activities of key reactive oxygen species (ROS)-scavenging enzymes, suppressed H2O2 and superoxide accumulation, and reduced malondialdehyde content and electrolyte leakage, thereby preserving cellular homeostasis. This study provides functional evidence for the positive regulatory role of VyMYB24 in cold tolerance via heterologous expression, underscores the genetic value of ‘Yanshan’ grape germplasm, and lays a preliminary foundation for improving crop stress resistance through the utilization of native wild germplasm genes.