<i>UvCYP503</i> is required for stress response and pathogenicity in <i>Ustilaginoidea virens</i>

The fungus <i>Ustilaginoidea virens</i>, which impacts rice spikes, causes rice false smut (RFS), a significant prevalent disease in rice cultivation regions globally. Cytochrome <i>P450</i> genes are known to be involved in secondary metabolism and pathogenesis in various species, but studies on <i>CYP450</i> genes in <i>U. virens</i> are limited. In this research, a <i>P450</i> family gene, <i>CYP503</i>, was found up-regulated during invasion stage of <i>U. virens</i>. Observation of fluorescence indicated that UvCYP503-GFP is situated within cytoplasm of hyphae. Disruption of <i>CYP503</i> led to decreased hyphal development, conidiation, and pathogenicity. Additional RNA-seq assay revealed that <i>UvCYP503</i> affects the transcript of genes associated with pathogenicity, various stress responses, and other <i>CYP450</i> genes. In alignment with RNA-seq results, compared with wild-type, Δ<i>Uvcyp503</i> mutants showed increased sensitivity to cell wall stresses, but reduced sensitivity to osmotic and hyperosmotic stressors. Moreover, Δ<i>Uvcyp503</i> mutants exhibited decreased sensitivity to the fungicides difenoconazole and tebuconazole. This study represents a phenome-based functional analysis of a <i>CYP503</i> gene in <i>U. virens</i> and provides valuable genetic resources for further research in filamentous fungi and other plant pathogens.