Snf1 promotes lignocellulose degradation by phosphorylating and activating transcription factor Swi6 in Ganoderma lucidum

Fungal cellulases including endoglucanases, exoglucanases, and β-glucosidases, synergistically degrade lignocellulose. While sucrose non-fermenting 1 (Snf1), a conserved eukaryotic regulator of carbon metabolism, is known to modulate cellulase production, its specific roles in β-glucosidase regulation, and the underlying mechanisms, remained unclear. Here, we demonstrate that Snf1 orchestrates cellulolytic activity by phosphorylating Swi6 at a conserved serine residue in Ganoderma lucidum . Phosphorylated Swi6 binds to the promoters of β-glucosidase genes bg1 and bg4 , elevating their expression and enzymatic activity. Cellulose triggers this Snf1-dependent Swi6 activation, whereas genetic disruption of snf1 or swi6 impairs bg1/4 transcription, β-glucosidase activity, and mycelial growth on lignocellulosic substrates. Pharmacological Snf1 activation rescues these defects in a Swi6-dependent manner, confirming Swi6 as the pivotal effector of Snf1-mediated lignocellulose degradation. These findings indicate that Snf1 enhances the transcriptional activity of Swi6 on the bg1/4 genes through phosphorylation, thereby upregulating cellulase production. Overall, the activation of Snf1-Swi6- bg1/4 pathway is an important regulatory mechanism for lignocellulose degradation in G. lucidum .