The APSES transcription factor Swi6B upregulates <i>CATALASE 1</i> transcription to enhance oxidative stress tolerance of <i>Ganoderma lucidum</i>

As sessile organisms, fungi often encounter various stresses throughout their lifespan, resulting in the overproduction of reactive oxygen species, which impedes the normal growth of fungi. Previously, we revealed that the Swi6B transcription factor is involved in the stress tolerance of <i>Ganoderma lucidum</i>. However, the underlying molecular mechanism is unclear. The present study demonstrated that oxidative stress increased the levels of Swi6B. Direct binding of Swi6B to the promoter region of <i>catalase 1</i> (<i>CAT1</i>) resulted in increased transcription of <i>CAT1</i> and reduced H₂O₂ levels in <i>SWI6B</i> overexpressing strains. In addition to increased Swi6B protein, the phosphorylation level of Swi6B was increased by H₂O₂ treatment. The overexpression of <i>SLT2</i>, a mitogen-activated protein kinase that interacts with Swi6B, increased the phosphorylation level of Swi6B, and treatment with H₂O₂ further enhanced this increase. As a result, both the binding of Swi6B to the <i>CAT1</i> gene and tolerance to H₂O₂ were increased in <i>SLT2</i>-overexpressing strains. The present findings revealed that the Slt2-Swi6B-CAT1 pathway responds to oxidative stress and contributes to improving the survival of <i>G. lucidum</i> in adverse environments.IMPORTANCEIn fungi, environmental stress leads to the accumulation of intracellular reactive oxygen species and leads to oxidative stress. Here, we found that the overexpression of the APSES transcription factor <i>Swi6B</i> enhances tolerance to oxidative stress in <i>Ganoderma lucidum</i>. Swi6B binds to the promoter region of <i>CAT1</i>, which increases <i>CAT1</i> transcription and reduces the H₂O₂ levels. In addition, the phosphorylation of Swi6B by Slt2 promotes the regulation of <i>CAT1</i> by Swi6B. The Slt2-Swi6B-CAT1 pathway is important for the response of <i>G. lucidum</i> to oxidative stress.