An ADP-ribosylation factor, BbarfA, is involved in conidial germination and virulence in Beauveria bassiana

Abstract:

[Objective] To understand the number of ADP-ribosylation factor (ARFs) and their roles in Beauveria bassiana.[Methods] ARFs were identified by BLASTp searching against the database of B. bassiana proteins and analyzed using molecular phylogenetics. Role of an ARF in fungal growth, stress responses and virulence was characterized by analysis of the gene transcription pattern, and investigation of the genetically modified B. bassiana strains.[Results] At least six ARFs and ARF-like proteins (ARFLs) were identified in B. bassiana, which were distributed in different groups of yeast Saccharomyces cerevisiae and human Homo sapiens ARFs and ARFLs. One of ARFs, BBA_01574, designated BbarfA, was clustered in the group of human ARF3, ARF4 and ARF5. Transcription levels of BbarfA were obviously higher in the mature conidia or during the isotropic growth (swelling) phase of conidia than those during germ tube elongation phase. Antisense inhibition of BbarfA accelerated conidial germination and resulted in an increase in fungal virulence, whereas overexpression of BbarfA and the gene with site-mutation in GTP-binding sequences (BbarfA^Q71I) caused the opposite phenotypes. Although expression of the gene was induced by high salt, osmotic, oxidative and high temperature stresses, no obvious difference was noted in sensitivities to these adverse stresses in all the genetically modified transformants, which included strains suppressing (by antisense inhibition) or overexpressing BbarfA, overexpressing the genes with site-mutation in GTP-dissociating (BbarfA^D26G) or GTP-binding (BbarfA^Q71I) sequences, and the wild type strains.[Conclusion] ADP-ribosylation factor, BbarfA, was involved in conidial germination and virulence in B. bassiana.