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

Abstract

Summary 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 Gα, Gβ and Gγ subunits, is involved in transducing signals from external stimuli to regulate downstream signal transduction pathways. Previously, we demonstrated that Gβ protein FvGbb1 directly impacts fumonisin regulation but not other physiological aspects in F. verticillioides. In this study, we identified and characterized a RACK1 (Receptor for Activated C Kinase 1) homolog FvGbb2 as a putative Gβ‐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 associate with diverse proteins in the cytoplasm to regulate vegetative growth, virulence, fumonisin biosynthesis and stress response in F. verticillioides.

Two Regulators of G-protein signaling (RGS) proteins FlbA1 and FlbA2 differentially regulate fumonisin B1 biosynthesis in Fusarium verticillioides

“…F. verticillioides M3125 was used as the wild-type strain in this study (Yan and Shim 2020). For growth and conidia production, all strains were grown on 0.2xPDA, myro, YEPD and V8 agar plates as described previously (Yan, et al 2019).…”

“…For growth and conidia production, all strains were grown on 0.2xPDA, myro, YEPD and V8 agar plates as described previously (Yan, et al 2019). Spore germination assay was performed following our previously described methods (Yan and Shim 2020). For carbon utilization assay, Czapek-Dox agar was modified with various carbon sources such as sucrose (10g/L), dextrose (10g/L), fructose (10g/L) and xylose (10g/L) (Yan, et al 2019).…”

“…All experiments were performed with at least three replicates. Inhibition rate was calculated as described previously (Yan and Shim 2020).…”

“…Both ΔFvflbA1 and ΔFvflbA2 knockout mutants were generated in the wild-type strain via split-marker approach (Yan and Shim 2020). Briefly, partial hygromycin B phosphotransferase gene ( HPH ) designated as PH (929bp) and HP (765bp) were used to fuse with left and right flanking regions of the targeted gene with joint-PCR approach.…”

“…Our earlier studies showed that functions of F. verticillioides Gβ and Gβ-like proteins are positively associated with FB1 production (Sagaram and Shim 2007, Yan and Shim 2020). Furthermore, transcription levels of four RGS genes FLBA1, FLBA2, RGSB , and RGSC1 were significantly altered in Gβ deletion mutant ΔFvgbb1 when compared to the wild-type F. verticillioides strain (Mukherjee, et al 2011).…”