Overexpression of TUF1 restores respiratory growth and fluconazole sensitivity to a Cryptococcus neoformans vad1Δ mutant

Abstract

The yeast-like fungusCryptococcus neoformansfavours respiration as a mechanism of energy production, and thus depends heavily on mitochondrial function. Previous studies of aC. neoformansvad1Δ mutant revealed reduced expression of the mitochondrial elongation factorTUF1and defects in glycerol utilization, consistent with mitochondrial dysfunction. In this study, we found thatin transexpression ofTUF1in thevad1Δ mutant suppressed the mitochondrial defects, including growth on respiration-dependent carbon sources and fluconazole resistance, associated withVAD1deletion. Tetracycline, an inhibitor of mitochondrial translation, was found to confer resistance to fluconazole in the wild-type andvad1Δ mutant, whereas the fluconazole susceptibility of theTUF1-overexpressing strain was unaffected by tetracycline treatment. In the presence of fluconazole, thevad1Δ mutant exhibited increased activation of the global transcriptional regulator Sre1.TUF1overexpression failed to alter cleavage of Sre1 in response to fluconazole in thevad1Δ mutant, suggesting thatTUF1repression in thevad1Δ mutant is distal to Sre1, or that it occurs through an independent pathway.