Functions of a Glucan Synthase Gene GFGLS in Mycelial Growth and Polysaccharide Production of Grifola frondosa

Glucan synthase (GLS) gene is known to be involved in the fungal biosynthesis of cell wall, differentiation, and growth. In the present study, a glucan synthase gene (GFGLS) in the edible mushroom Grifola frondosa with a full sequence of 5927 bp encoding a total of 1781 amino acids was cloned and characterized for the first time. GFGLSp is a membrane protein containing two large transmembrane domains connected with a hydrophilic cytoplasmic domain. With a constructed dual promoter RNA silencing vector pAN7-gfgls-dual, a GFGLS-silencing transformant iGFGLS-3 had the lowest GFGLS transcriptional expression level (26.1%) with a shorter length and thinner appearance of the mycelia, as well as decreased mycelial biomass and exo-polysaccharide production of 5.02 and 0.38 g/L, respectively. Further analysis indicated that GFGLS silence influenced slightly the monosaccharide compositions and ratios of mycelial and exo-polysaccharide. These findings suggest that GFGLS could affect mycelial growth and polysaccharide production by downregulating the glucan synthesis.