G Protein α Subunit GpaB is Required for Asexual Development, Aflatoxin Biosynthesis and Pathogenicity by Regulating cAMP Signaling in Aspergillus flavus.

The heterotrimeric G proteins are critical for signal transduction and function in numerous biological processes including vegetative growth, asexual development and fungal virulence in fungi. Here, we identified four G protein alpha subunits (GanA, GpaB, FadA and GaoC) in the notorious Aflatoxin-producing fungus . GanA, GpaB and FadA have homologues in other fungal species, while GaoC is a novel one. Here, we showed that the loss function of displayed a defect in conidiophore formation and considerably reduced expression levels of conidia-specific genes and . A decreased viability of cell wall integrity stress and oxidative stress were also found in the ∆ mutant. More importantly, aflatoxin (AF) biosynthesis and infection on crop seeds were severely impaired in the -deficient mutant. Further analyses demonstrated that the intracellular cAMP levels significantly reduced in the -deficient mutant compared to wildtype strains. Additionally, an alteration of PKA activities in the ∆ mutant was also found. Overall, our results indicated that GpaB played diverse roles in asexual sporulation, AF biosynthesis and virulence by regulating cAMP signaling in .