UvSnx4 is required for conidiation, pathogenicity and stress responses by regulating mitophagy and macroautophagy in Ustilaginoidea virens.

Rice false smut disease, caused by the biotrophic fungus Ustilaginoidea virens, threatens rice production and quality. SNX family proteins have a Phox domain in the structure, playing important roles in protein transport and sorting in the endocytic pathway. However, the roles and underlying mechanisms controlled by SNX proteins in development and pathogenicity are still poorly understood in U. virens. Here, we characterized the SNX family protein Snx4 in U. virens. The transcriptional levels of UvSNX4 were upregulated at the invasive growth stage. Deletion of UvSNX4 resulted in defects in mycelial growth, conidiation, pathogenicity, and stress adaptations. Microscopic observation showed that UvSnx4 partially colocalized with mitochondria. Furthermore, UvSnx4 is required for mitophagy and macroautophagy, which are critical for conidiation and pathogenicity in U. virens. Moreover, UvSnx4 interacted with the autophagy-related core proteins UvAtg11, UvAtg20, and UvAtg17. In conclusion, our studies suggested that UvSnx4 contributes to development, stress adaptation, and pathogenicity via involvement in mitophagy and autophagy in U. virens, which provides insight into the biological functions of SNX proteins in biotrophic filamentous fungi.