Abstract

Downy mildew caused by oomycete pathogenPlasmopara viticolais a devastating disease of grapevine.P. viticolasecretes an array of RXLR effectors to enhance virulence. One of these effectors, PvRXLR131, has been reported to interact with grape (Vitis vinifera) BRI1 kinase inhibitor (VvBKI1). BKI1 is conserved inNicotiana benthamianaandArabidopsis thaliana. However, the role of VvBKI1 in plant immunity is unknown. Here, we found transient expression ofVvBKI1in grapevine andN. benthamianaincreased its resistance toP. viticolaandPhytophthora capsici, respectively. Furthermore, ectopic expression of VvBKI1 in Arabidopsis can increase its resistance to downy mildew caused byHyaloperonospora arabidopsidis. Further experiments revealed that VvBKI1 interacts with a cytoplasmic ascorbate peroxidase, VvAPX1, an ROS-scavenging protein. Transient expression ofVvAPX1in grape andN. benthamianapromoted its resistance againstP. viticola, andP. capsici. Moreover,VvAPX1transgenic Arabidopsis is more resistant toH. arabidopsidis. Furthermore, both VvBKI1 and VvAPX1 transgenic Arabidopsis showed an elevated ascorbate peroxidase activity and enhanced disease resistance. In summary, our findings suggest a positive correlation between APX activity and resistance to oomycetes and that this regulatory network is conserved inV. vinifera,N. benthamiana, andA. thaliana.Keywords:VvBKI1;VvAPX1;oomycete;downy mildew;resistance