14-3-3 proteins are involved in growth, hyphal branching, ganoderic acid biosynthesis, and response to abiotic stress in Ganoderma lucidum.

ABSTRACT

Ganoderma lucidum, which contains many pharmacologically active compounds, is regarded as a traditional medicinal fungus. Nevertheless, the scarcity of basic research limits the commercial value and utilization of G. lucidum. As a class of highly conserved, phosphopeptide-binding proteins present in all eukaryotes, 14-3-3 proteins play vital roles in controlling multiple physiological processes, including signal transduction, primary metabolism, and stress responses. However, knowledge of the roles of 14-3-3 proteins in Basidiomycetes is sparse. In this article, two homologs of 14-3-3 proteins, encoded by the two distinct genes GlBmh1 and GlBmh2, were distinguished in G. lucidum. We found that GlBmh1 and GlBmh2 were expressed at various developmental stages, including in vegetative mycelium cultivated on solid medium and in primordia and fruiting bodies. Moreover, we constructed GlBmh1 single-silenced strains, GlBmh2 single-silenced strains, and 14-3-3 double-silenced mutants for further study. When GlBmh1 and GlBmh2 were inhibited by RNA interference, the growth rate of mycelia was decreased, and the distance between the aerial hyphal branches was reduced; responses to various abiotic stresses such as oxidants and cell wall and osmotic stressors were also changed. Furthermore, the contents of secondary metabolite ganoderic acids (GAs) were increased after GlBmh1 and GlBmh2 were simultaneously silenced. Taken together, we provide evidence that implicates potential roles for the two 14-3-3 proteins in affecting growth and GA biosynthesis, thereby providing new insights into the basic functions of 14-3-3 proteins in G. lucidum.