RNA sequencing analysis identifies the metabolic and developmental genes regulated by BbSNF1 during conidiation of the entomopathogenic fungus Beauveria bassiana

Conidiation promotes fungal dispersal and survival in the environment, and is a determinant for the biocontrol potential of Beauveria bassiana. The SNF1/AMPK protein kinases function as an important regulator of fungal development and energy metabolism, and play a crucial role in conidiation of the filamentous fungi. In previous study, it has been established that the B. bassiana homolog (BbSNF1) controls conidial production. This study showed that the Delta BbSNF1 mutants displayed a delayed development of mycelia and conidia, but the conidiophore morphogenesis was not significantly changed in the mutants. Ablation of BbSNF1 significantly changed the metabolic homeostasis of intracellular amino acids during conidiation, and caused a notable reduction in the contents of seven amino acids (i.e., arginine, alanine, valine, phenylalanine, lysine, leucine, and glutamic acid). All above amino acids could recover conidiation of the mutants in different extents (ranging from 43.3 to 300 %). Transcriptomic analysis revealed many putative target genes regulated by BbSNF1 and associated with conidial development, and these genes were primarily involved in metabolism, cell rescue, and transport. Particularly, four categories related to the amino acid degradation were over-represented in the up-regulated genes, and three categories related to the amino acid biosynthesis were over-represented in the down-regulated genes. Moreover, the Delta BbSNF1 mutants displayed reduced expression level of the upstream and central regulators of conidiation, as well as the other regulator and cytoskeleton genes. Our data indicate that SNF1 kinase contributes to B. bassiana conidiation by regulating the metabolism and the central regulators of conidiation.