<i>Phytophthora sojae</i> Effector PsCRN70 Suppresses Plant Defenses in <i>Nicotiana benthamiana</i>

<div><p><i>Phytophthora sojae</i>, an oomycete pathogen, produces a large number of effector proteins that enter into host cells. The Crinklers (Crinkling and Necrosis, CRN) are cytoplasmic effectors that are conserved in oomycete pathogens and their encoding genes are highly expressed at the infective stages in <i>P. sojae</i>. However, their roles in pathogenesis are largely unknown. Here, we functionally characterized an effector <i>PsCRN70</i> by transiently and stably overexpressing it in <i>Nicotiana benthamiana</i>. We demonstrated that PsCRN70 was localized to the plant cell nucleus and suppressed cell death elicited by all the tested cell death-inducing proteins, including BAX, PsAvh241, PsCRN63, PsojNIP and R3a/Avr3a. Overexpression of the <i>PsCRN70</i> gene in <i>N. benthamiana</i> enhanced susceptibility to <i>P. parasitica</i>. The H₂O₂ accumulation in the <i>PsCRN70</i>-transgenic plants was reduced compared to the <i>GFP</i>-lines. The transcriptional levels of the defense-associated genes, including <i>PR1b</i>, <i>PR2b</i>, <i>ERF1</i> and <i>LOX</i>, were also down-regulated in the <i>PsCRN70</i>-transgenic lines. Our results suggest that PsCRN70 may function as a universal suppressor of the cell death induced by many elicitors, the host H₂O₂ accumulation and the expression of defense-associated genes, and therefore promotes pathogen infection.</p>