The putative monomeric G-protein GBP1 is negatively associated with fumonisin B1 production in Fusarium verticillioides

Fumonisin B-1 (FB1) is a mycotoxin produced by Fusarium verticillioides that contaminates maize. FB1 has been linked to a number of human and animal mycotoxicoses worldwide. Despite its significance, our understanding of the FB1 biosynthesis regulatory mechanisms is limited. Here, we describe F. verticillioides GBP1, encoding a monomeric G-protein, and its role in FB1 biosynthesis. GBP1 was discovered as an expressed sequence tag (EST) up-regulated in the F. verticillioides fcc1 mutant that showed reduced conidiation and no FB1 biosynthesis when grown on maize kernels. Sequence analysis showed that GBP1 encodes a putative 368-amino-acid protein with similarity to DRG and Obg subclasses of G-proteins that are involved in development and stress responses. A GBP1 knockout mutant (Delta gbp1) exhibited normal growth, but increased FB1 production (> 58%) compared with the wild-type when grown on corn kernels. Complementation of Delta gbp1 with the wild-type GBP1 gene restored FB1 production levels to that of the wild-type. Our data indicate that GBP1 is negatively associated with FB1 biosynthesis but not with conidiation in F. verticillioides. The deletion of GBP1 led to up-regulation of key FB1 biosynthetic genes, FUM1 and FUM8, suggesting that the increased FB1 production in Delta gbp1 is due to over-expression of FUM genes.