GlSlt2 positively regulates GlMyb-mediated cellulose utilization in Ganoderma lucidum.

Fungal degradation of cellulose facilitates the sustainable harnessing of biosphere energy and carbon cycling. Ganoderma lucidum is one of the basidiomycetes with the largest number of hydrolytic enzymes in its genome. The mycelium of G. lucidum degrades cellulose through the production of substantial amounts of cellulase, enabling the absorption of carbon sources and nutrients essential for fruiting body development. The efficiency with which G. lucidum utilizes cellulose is a determinant of its growth rate. In this study, our findings revealed that the mitogen-activated protein kinase GlSlt2 positively modulates cellulase activity and cellulose utilization. Furthermore, a yeast two-hybrid (Y2H) screening library found that GlSlt2 interacts with GlMyb, an R2R3-type MYB transcription factor. Further studies revealed that GlSlt2 phosphorylates the S245 site of GlMyb and that GlMyb positively regulates cellulose utilization. GlMyb directly binds to the [A/G] TTAC [G/C] [C/G] motif on the promoters of cellulase-related genes. The S245 site of GlMyb promotes the binding of GlMyb to the promoters of cellulase-related genes. Collectively, our findings highlight the mechanism by which GlSlt2 positively regulates GlMyb-mediated cellulose utilization. Enhancing cellulose utilization efficiency lays the foundation for the degradation of cellulose in agricultural and forestry waste and facilitates biomass conversion.

Importance: The proficient exploitation of cellulose is pivotal for fostering sustainable development, safeguarding the environment, and advancing economic prosperity and technological innovation. Paramount among these benefits is the reduction of reliance on fossil fuels. Ganoderma lucidum, a filamentous fungus, could effectively utilize cellulose from agricultural and forestry waste. Nevertheless, enhancing the efficiency of cellulose utilization from these by-products presents a formidable challenge that demands resolution. In our study, we discovered that GlSlt2 interacts with GlMyb and phosphorylates the S245 site of GlMyb. Further studies have revealed that GlSlt2 positively regulates GlMyb-mediated cellulose utilization. In summary, our findings unveil a sophisticated regulatory mechanism controlling cellulose utilization. These insights lay the foundation for biomass conversion and the biosphere carbon cycle.