Essential Role of CgErg6p in Maintaining Oxidative Stress Tolerance and Iron Homeostasis in Candida glabrata

The human pathogenic fungus Candida glabrata is the second leading cause of candidemia, a life-threatening invasive mycosis. Clinical outcomes are complicated by reduced susceptibility of C. glabrata to azoles together with its ability to evolve stable resistance to both azoles and echinocandins following drug exposure. Compared to other Candida spp., C. glabrata displays robust oxidative stress resistance. In this study, we investigated the impact of CgERG6 gene deletion on the oxidative stress response in C. glabrata. CgERG6 gene encodes sterol-24-C-methyltransferase, which is involved in the final steps of ergosterol biosynthesis. Our previous results showed that the Cgerg6Δ mutant has a lower ergosterol content in its membranes. Here, we show that the Cgerg6Δ mutant displays increased susceptibility to oxidative stress inducing agents, such as menadione, hydrogen peroxide and diamide, accompanied with increased intracellular ROS production. The Cgerg6Δ mutant is not able to tolerate higher concentrations of iron in the growth media. We observed increased expression of transcription factors, CgYap1p, CgMsn4p and CgYap5p, together with increased expression of catalase encoding the CgCTA1 gene and vacuolar iron transporter CgCCC1 in the Cgerg6Δ mutant cells. However, it seems that the CgERG6 gene deletion does not influence the function of mitochondria.