Characterization of non-canonical G beta-like protein FvGbb2 and its relationship with heterotrimeric G proteins in Fusarium verticillioides

Fusarium verticillioides is a fungal pathogen that is responsible for maize ear rot and stalk rot diseases worldwide. The fungus also produces carcinogenic mycotoxins, fumonisins, on infested maize. Unfortunately, we still lack clear understanding of how the pathogen responds to host and environmental stimuli to trigger fumonisin biosynthesis. The heterotrimeric G protein complex, consisting of canonical G, G{beta}, and G{gamma} subunits, is involved in transducing signals from external stimuli to regulate downstream signal transduction pathways. Previously, we demonstrated that G{beta} protein FvGbb1 has direct impact on fumonisin regulation but no other physiological aspects in F. verticillioides. In this study, we identified and characterized a putative receptor for activated C kinase 1 (RACK1) homolog FvGbb2 as a putative G{beta}-like protein in F. verticillioides. The mutant exhibited severe defects not only in fumonisin biosynthesis but also vegetative growth and conidiation. FvGbb2 was positively associated with carbon source utilization and stress agents but negatively regulated general amino acid control. While FvGbb2 does not interact with canonical G protein subunits, it may interact with diverse proteins in the cytoplasm to regulate vegetative growth, virulence, fumonisin biosynthesis, and stress response in F. verticillioides.