CWI Pathway and Autophagy Co-Regulate Virulence by MoAtg4 Phosphorylation in Magnaporthe oryzae

Abstract

Cell wall integrity (CWI) signaling pathway and macroautophagy/autophagy are crucial for maintaining cellular homeostasis. We previously reported that autophagy-related (Atg) protein phosphorylates CWI component to regulate virulence in Magnaporthe oryzae. However, the interplay between CWI signaling pathway and autophagy, and how they jointly regulate pathogen development and virulence, remains elusive. Here, we identify MoAtg4 phosphorylation as a key connection between CWI signaling pathway and autophagy, which targets the cleavage and recycling of MoAtg8. CWI core component MoMkk1 phosphorylates MoAtg4 in the cytoplasm to attenuate C-terminal cleavage of MoAtg8. Furthermore, MoAtg1-mediated MoAtg4 phosphorylation at the phagophore assembly site inhibits recycling of cleaved MoAtg8. Importantly, the two MoAtg4 phosphorylation events coordinately regulate development and virulence by maintaining proper autophagy. Taken together, our findings reveal a connection between CWI signaling pathway and autophagy through an Atg protein phosphorylation, which plays a pivotal regulatory role in the development and virulence of the blast fungus.

Keywords: Cell wall integrity (CWI), Autophagy, protein phosphorylation, appressorium, pathogenicity, Magnaporthe oryzae