The RXLR Effector PcAvh1 Is Required for Full Virulence of <i>Phytophthora capsici</i>

Abstract

Plant pathogens employ diverse secreted effector proteins to manipulate host physiology and defense in order to foster diseases. The destructive <i>Phytophthora</i> pathogens encode hundreds of cytoplasmic effectors, which are believed to function inside the plant cells. Many of these cytoplasmic effectors contain the conserved N-terminal RXLR motif. Understanding the virulence function of RXLR effectors will provide important knowledge of <i>Phytophthora</i> pathogenesis. Here, we report the characterization of RXLR effector PcAvh1 from the broad-host range pathogen <i>Phytophthora capsici</i>. Only expressed during infection, <i>PcAvh1</i> is quickly induced at the early infection stages. CRISPR/Cas9-knockout of <i>PcAvh1</i> in <i>P. capsici</i> severely impairs virulence while overexpression enhances disease development in <i>Nicotiana benthamiana</i> and bell pepper, demonstrating that PcAvh1 is an essential virulence factor. Ectopic expression of PcAvh1 induces cell death in <i>N. benthamiana</i>, tomato, and bell pepper. Using yeast two-hybrid screening, we found that PcAvh1 interacts with the scaffolding subunit of the protein phosphatase 2A (PP2Aa) in plant cells. Virus-induced gene silencing of <i>PP2Aa</i> in <i>N. benthamiana</i> attenuates resistance to <i>P. capsici</i> and results in dwarfism, suggesting that PP2Aa regulates plant immunity and growth. Collectively, these results suggest that PcAvh1 contributes to <i>P. capsici</i> infection, probably through its interaction with host PP2Aa.