The abscisic acid receptor gene VvPYL4 positively regulates grapevine resistance to Plasmopara viticola

Downy mildew is one of the most serious diseases threatening grapevine cultivation. The PYR/PYL/RCAR proteins, which act as abscisic acid (ABA) receptors, are multifunctional, highly conserved, and reportedly play a crucial role in plant stress resistance in the ABA signaling pathway. In this study, we cloned a putative abscisic acid receptor gene, VvPYL4, from the ‘Beta’ grapevine cultivar. An analysis of the subcellular localization demonstrated that overexpressed VvPYL4 was localized in both the cytoplasm and the nucleus. The resistance of grapevine cultivars to downy mildew increased after the application of the exogenous hormones MeJA and ABA. The expression of VvPYL4 was significantly induced when exposed to Plasmopara viticola, MeJA, and ABA. The transcript of the VvPYL4 gene in ‘Beta’ grapevine leaves treated with tobacco rattle virus-induced gene silencing (VIGS) was significantly down-regulated. Silencing VvPYL4 had a slight effect on P. viticola resistance. Furthermore, silencing VvPYL4 significantly altered the transcripts of ABA and JA responsive genes, including the ABA signaling pathway-related genes ABF1, SnRK2.2, and PP2C2, as well as the genes related to the JA signaling pathway, MYC2, JAR1, and JAZ. Altogether, the data provide new evidence that VvPYL4 positively regulates grapevine response to downy mildew. This study also discusses the regulation mechanism of VvPYL4 on ABA and JA signaling transduction. Finally, these results provide a basis for additional research on the mechanisms behind grapevine resistance to downy mildew.