N <i>-</i> glycosylation shields <i>Phytophthora sojae</i> apoplastic effector PsXEG1 from a specific host aspartic protease

Abstract

Significance The apoplastic space is the initial battlefield in plant–microbe interactions. However, the molecular mechanisms underlying how apoplastic immunity controls pathogen invasion is still largely unknown. Here, we show that soybean secretes an apoplastic aspartic protease, GmAP5, that binds to and degrades PsXEG1 to block its contribution to virulence. Phytophthora sojae , however, employs N-glycosylation as a shield to protect PsXEG1 from degradation by GmAP5. N-glycosylation of PsXEG1 also attenuates the binding by the inhibitor GmGIP1. Our result uncovers an additional layer of defense and counterdefense centered on PsXEG1, highlighting an example in which N - glycosylation of a pathogen virulence factor tips the balance of an arms race in host–pathogen conflicts.