The E2 ubiquitin-conjugating enzyme CfRad6 regulates the autophagy and pathogenicity of Colletotrichum fructicola on Camellia oleifera

Abstract

AbstractAnthracnose is a common disease found in Camellia oleifera producing areas across China, whose primary pathogen is Colletotrichum fructicola. We previously revealed that autophagy is essential for the pathogenicity of C. fructicola. However, the function of ubiquitin–proteasome system (UPS), which is a parallel protein degradation pathway to autophagy, remains elusive. Here, we report that CfRad6, an E2 conjugating enzyme in UPS, interacts with three putative E3 ubiquitin ligases, namely CfRad18, CfUbr1, and CfBre1. Importantly, we presented evidence showing that CfRad6 negatively regulates autophagy, revealing the first link between UPS and autophagy in pathogenic fungi. Targeted gene deletion showed that CfRad6 is involved in growth and conidiation. We further found that the ΔCfrad6 mutant is defective in appressoria formation and responses to environmental stresses. These combined effects, along with the abnormal autophagy level, lead to the pathogenicity defects of the ΔCfrad6 mutant. Taken together, our study indicates the pleiotropic functions of CfRad6 in the development and pathogenicity of C. fructicola.