Mitochondrial complex III subunit Qcr8 regulates the virulence and adhesion of <i>Candida albicans</i> by modulating mitochondrial function

Invasive fungal infections caused by <i>Candida albicans</i> pose significant clinical challenges due to their high mortality rates and emerging drug resistance. In this study, we established Qcr8, an accessory subunit of mitochondrial complex III, as a critical virulence determinant in <i>C. albicans</i>. The deletion of <i>QCR8</i> markedly attenuated virulence in both <i>Galleria mellonella</i> and murine infection models, concomitant with impaired adhesion to biotic (human umbilical vein endothelial cells) and abiotic surfaces. Mechanistically, <i>QCR8</i> deletion disrupted mitochondrial homeostasis, evidenced by elevated reactive oxygen species levels, diminished membrane potential (ΔΨm), and reduced ATP levels. Notably, cAMP levels decreased in mutant strains, resulting in the pronounced downregulation of Ras/cAMP/protein kinase A (PKA) pathway components (<i>RAS1</i>, <i>CYR1</i>, <i>TPK1/2</i>, <i>EFG1</i>, and <i>FLO8</i>), while exogenous cAMP supplementation partially restored the adhesion capacity. Our findings indicate that Qcr8 plays a vital role in mitochondrial complex III, highlighting its therapeutic potential as a fungus-specific drug target.IMPORTANCEWe identified Qcr8, an accessory subunit of mitochondrial complex III for <i>C. albicans</i> full virulence. This study indicates that the accessory subunit of complex III, in addition to the structural subunits that have been previously the focus of study, also plays a significant role in the regulation of virulence. We also elucidated that Qcr8 promotes virulence via the Ras/cAMP/PKA pathway. Our findings established Qcr8 as a potential therapeutic target for treating <i>C. albicans</i> infections, which is particularly relevant, given the rising concern about antifungal resistance.