Characterization of Virulence Function of Pseudomonas cichorii Avirulence Protein E1 (AvrE1) during Host Plant Infection

Abstract

<i>Pseudomonas cichorii</i> secretes effectors that suppress defense mechanisms in host plants. However, the function of these effectors, including avirulence protein E1 (AvrE1), in the pathogenicity of <i>P. cichorii</i>, remains unexplored. In this study, to investigate the function of <i>avrE1</i> in <i>P. cichorii</i> JBC1 (PcJBC1), we created an <i>avrE1</i>-deficient mutant (JBC1^ΔavrE1) using CRISPR/Cas9. The disease severity caused by JBC1^ΔavrE1 in tomato plants significantly decreased by reducing water soaking during early infection stage, as evidenced by the electrolyte leakage in infected leaves. The disease symptoms caused by JBC1^ΔavrE1 in the cabbage midrib were light-brown spots compared to the dark-colored ones caused by PcJBC1, which indicates the role of AvrE1 in cell lysis. The <i>avrE1</i>-deficient mutant failed to elicit cell death in non-host tobacco plants. Disease severity and cell death caused by JBC1^ΔavrE1 in host and non-host plants were restored through heterologous complementation with <i>avrE1</i> from <i>Pseudomonas syringae</i> pv. <i>tomato</i> DC3000 (PstDC3000). Overall, our results indicate that <i>avrE1</i> contributes to cell death during early infection, which consequently increases disease development in host plants. The roles of PcJBC1 AvrE1 in host cells remain to be elucidated.