The putative monomeric G-protein GBP1 is negatively associated with fumonisin B₁ production in Fusarium verticillioides
2006
SAGARAM, UMA SHANKAR | BUTCHKO, ROBERT A.E. | SHIM, WON-BO
Fumonisin B₁ (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 (Δgbp1) exhibited normal growth, but increased FB₁ production (> 58%) compared with the wild-type when grown on corn kernels. Complementation of Δgbp1 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 Δgbp1 is due to over-expression of FUM genes.
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