NAD⁺-dependent Glsirt1 has a key role on secondary metabolism in Ganoderma lucidum

Nicotinamide adenine dinucleotide (NAD⁺) is an important intracellular metabolite that is involved in different cel1lular processes. Glnmnat is the key enzyme that can affect intracellular NAD⁺ content. Here, we found that exogenous NAD⁺ treatment significantly increased ganoderic acid (GA) content in Ganoderma lucidum by 56.2%. Further experimental results showed that the acetylation level in Glnmnat-silenced strains significantly increased by about 35% and the transcript level of deacetylase Glsirt1 decreased by about 70%. Moreover, silencing Glnmnat led to a decrease in GA content, and this decrease could be rescued by the Glsirt1 activator. In addition, the acetylation of Glsirt1i-11 and Glsirt1i-21 was significantly increased by 28.8% and 41.0%. Furthermore, the decrease in GA content caused by silencing Glsirt1 could not be completely rescued by NAD⁺ treatment. Taken together, our study reveals that Glsirt1 is essential for the downstream regulation of GA biosynthesis by Glnmnat/NAD⁺, emphasizes the importance of acetylation modification in the mechanism of GA biosynthesis, and provides ideas for other fungi to study secondary metabolic regulatory networks in epigenetics.