An R2R3-MYB transcription factor VyMYB24, isolated from wild grape Vitis yanshanesis J. X. Chen., regulates the plant development and confers the tolerance to drought

Abstract

In grapevines, the MYB transcription factors play an important regulatory role in the phenylpropanoid pathway including proanthocyanidin, anthocyanin, and flavonoid biosynthesis. However, the role of MYB in abiotic stresses is not clear. In this study, an R2R3-MYB transcription factor, <i>VyMYB24</i>, was isolated from a high drought-tolerant Chinese wild <i>Vitis</i> species <i>V. yanshanesis</i>. Our findings demonstrated that it was involved in plant development and drought tolerance. <i>VyMYB24</i> is a nuclear protein and is significantly induced by drought stress. When over-expressed in tobacco, <i>VyMYB24</i> caused plant dwarfing including plant height, leaf area, flower size, and seed weight. The GA1+3 content in transgenic plants was reduced significantly, and spraying exogenous gibberellin could recover the dwarf phenotype of <i>VyMYB24</i> transgenic plants, suggesting that <i>VyMYB24</i> might inhibit plant development by the regulation of gibberellin (GA) metabolism. Under drought stress, the <i>VyMYB24</i> transgenic plants improved their tolerance to drought with a lower wilting rate, lower relative electrical conductivity, and stronger roots. Compared to wild-type tobacco plants, <i>VyMYB24</i> transgenic plants accumulated less reactive oxygen, accompanied by increased antioxidant enzyme activity and upregulated gene expression levels of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) genes. In addition, transgenic plants accumulated more proline, and their related synthetic genes <i>NtP5CR</i> and <i>NtP5CS</i> genes were significantly upregulated when exposed to drought. Besides, abiotic stress-responsive genes, <i>NtDREB, NtERD10C, NtERD10D</i>, and <i>NtLEA5</i>, were upregulated significantly in <i>VyMYB24</i> transgenic plants. These results indicate that <i>VyMYB24</i> plays a positive regulatory role in response to drought stress and also regulates plant development, which provides new evidence to further explore the molecular mechanism of drought stress of the MYB gene family.