Grapevine VlbZIP30 improves drought resistance by directly activating VvNAC17 and promoting lignin biosynthesis through the regulation of three peroxidase genes

Drought stress severely affects grapevine quality and yield, and recent reports have revealed that lignin plays an important role in protection from drought stress. Since little is known about lignin-mediated drought resistance in grapevine, we investigated its significance. Herein, we show that VlbZIP30 mediates drought resistance by activating the expression of lignin biosynthetic genes and increasing lignin deposition. Transgenic grapevine plants overexpressing VlbZIP30 exhibited lignin deposition (mainly G and S monomers) in the stem secondary xylem under control conditions, which resulted from the upregulated expression of VvPRX4 and VvPRX72. Overexpression of VlbZIP30 improves drought tolerance, characterized by a reduction in the water loss rate, maintenance of an effective photosynthesis rate, and increased lignin content (mainly G monomer) in leaves under drought conditions. Electrophoretic mobility shift assay, luciferase reporter assays, and chromatin immunoprecipitation-qPCR assays indicated that VlbZIP30 directly binds to the G-box cis-element in the promoters of lignin biosynthetic (VvPRX N1) and drought-responsive (VvNAC17) genes to regulate their expression. In summary, we report a novel VlbZIP30-mediated mechanism linking lignification and drought tolerance in grapevine. The results of this study may be of value for the development of molecular breeding strategies to produce drought-resistant fruit crops.