Kinase Inhibitor VvBKI1 Interacts with Ascorbate Peroxidase VvAPX1 Promoting Plant Resistance to Oomycetes

Downy mildew caused by oomycete pathogen is a devastating disease of grapevine. secretes an array of RXLR effectors to enhance virulence. One of these effectors, PvRXLR131, has been reported to interact with grape ( ) BRI1 kinase inhibitor (VvBKI1). BKI1 is conserved in and . However, the role of VvBKI1 in plant immunity is unknown. Here, we found transient expression of in grapevine and increased its resistance to and , respectively. Furthermore, ectopic expression of VvBKI1 in Arabidopsis can increase its resistance to downy mildew caused by . Further experiments revealed that VvBKI1 interacts with a cytoplasmic ascorbate peroxidase, VvAPX1, an ROS-scavenging protein. Transient expression of in grape and promoted its resistance against , and . Moreover, transgenic Arabidopsis is more resistant to . 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 in , , and .