Regulation of Catalase Expression and Activity by DhHog1 in the Halotolerant Yeast Debaryomyces hansenii Under Saline and Oxidative Conditions

Efficient transcriptional regulation of the stress response is critical for microorganism survival. In yeast, stress-related gene expression, particularly for antioxidant enzymes like catalases, mitigates reactive oxygen species such as hydrogen peroxide (H₂O₂), preventing cell damage. The halotolerant yeast <i>Debaryomyces hansenii</i> shows oxidative stress tolerance, largely due to high catalase activity from <i>DhCTA</i> and <i>DhCTT</i> genes. This study evaluates <i>D. hansenii'</i>s response to oxidative stress caused by H₂O₂ under saline conditions, focusing on cell viability, gene expression, and catalase activity. Chromatin organization in the promoter of <i>DhCTA</i> and <i>DhCTT</i> was analyzed, revealing low nucleosome occupancy in promoter regions, correlating with active gene expression. Stress-related motifs for transcription factors like Msn2/4 and Sko1 were found, suggesting regulation by the <i>DhHog1</i> MAP kinase. Analysis of a <i>Dhhog1</i>Δ mutant showed <i>Dh</i>Hog1's role in <i>DhCTA</i> expression under H₂O₂ or NaCl conditions. These findings highlight <i>Dh</i>Hog1's critical role in regulating the stress response in <i>D. hansenii</i>, offering insights for enhancing stress tolerance in halotolerant yeasts, particularly for industrial applications in saline wastewater management.