UvCYP503 is required for stress response and pathogenicity in Ustilaginoidea virens.

The fungus Ustilaginoidea virens, which impacts rice spikes, causes rice false smut (RFS), a significant prevalent disease in rice cultivation regions globally. Cytochrome P450 genes are known to be involved in secondary metabolism and pathogenesis in various species, but studies on CYP450 genes in U. virens are limited. In this research, a P450 family gene, CYP503, was found up-regulated during invasion stage of U. virens. Observation of fluorescence indicated that UvCYP503-GFP is situated within cytoplasm of hyphae. Disruption of CYP503 led to decreased hyphal development, conidiation, and pathogenicity. Additional RNA-seq assay revealed that UvCYP503 affects the transcript of genes associated with pathogenicity, various stress responses, and other CYP450 genes. In alignment with RNA-seq results, compared with wild-type, ΔUvcyp503 mutants showed increased sensitivity to cell wall stresses, but reduced sensitivity to osmotic and hyperosmotic stressors. Moreover, ΔUvcyp503 mutants exhibited decreased sensitivity to the fungicides difenoconazole and tebuconazole. This study represents a phenome-based functional analysis of a CYP503 gene in U. virens and provides valuable genetic resources for further research in filamentous fungi and other plant pathogens.