Cytochrome <i>c</i> Oxidase Influences Pyraclostrobin Sensitivity in <i>Fusarium graminearum</i> by Regulating <i>FgAox</i> Through Transcription Factors FgAod2 and FgAod5

Cytochrome <i>c</i> oxidase (Cox) is a crucial terminal oxidase in the electron transport chain. In this study, we generated 14 Cox gene deletion or overexpression mutants in <i>Fusarium graminearum</i>. Fungicide sensitivity tests revealed that 11 Cox gene deletion mutants displayed resistance to pyraclostrobin, while 10 overexpression mutants showed hypersensitivity. RNA-Seq and RT-qPCR analyses demonstrated the upregulation of <i>FgAox</i> (alternative oxidase in <i>F. graminearum</i>), <i>FgAod</i>2, and <i>FgAod</i>5 (alternative oxidase deficiency in <i>F. graminearum</i>) in ΔFgCox4-2 and ΔFgCox17-75 mutants. In 11 Cox gene deletion mutants, <i>FgAox</i> expression was significantly upregulated, whereas in 10 Cox gene overexpression mutants, it was significantly downregulated. <i>FgAox</i> overexpression mutants exhibit resistance to pyraclostrobin, while <i>FgAox</i> deletion mutants show hypersensitivity to pyraclostrobin. FgAod2 and FgAod5 were identified as transcription factors for <i>FgAox</i>. Our findings reveal that <i>FgCox</i> influences pyraclostrobin sensitivity by regulating <i>FgAox</i> through FgAod2 and FgAod5. Understanding pyraclostrobin resistance mechanisms in <i>F. graminearum</i> could help develop better fungicide rotation and application strategies to manage resistance and guide the creation of new fungicides targeting different pathways.