Submitted to: Applied and Environmental Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/25/2003
Publication Date: 11/15/2003
Citation: Butchko, R.A., Plattner, R.D., Proctor, R. 2003. FUM9 is required for C-5 hydroxylation of fumonisins and complements the meitotically defined Fum3 locus in Gibberella moniliformis. Applied and Environmental Microbiology. 69(11):6935-6937. Interpretive Summary: Gibberella moniliformis is a fungus that can cause diseases such as ear and stalk rot of maize. Along with causing a disease on the plant, the fungus also produces a toxic chemical that can cause staggers in horses, lung disease in swine and has been shown to cause cancer in laboratory animals. We are trying to understand the biology of the fungus and how it relates to toxin production. We are interested in understanding the genetics underlying the biochemistry of toxin production. One way in which we study the function of individual genes is to eliminate the function of the gene by a process called gene knockout. In this study, we are interested in the function of a gene called FUM9 and its role in toxin production. We have knocked out the FUM9 gene and we have studies the effect of eliminating FUM9 on toxin production. In this case, we have found that FUM9 is necessary for a particular biochemical reaction during toxin production. This information has allowed us to understand more fully the biochemical process of toxin production. We hope to use this understanding to reduce the occurrence of this toxin in maize.
Technical Abstract: Fumonisins are mycotoxins produced by the fungus Gibberella moniliformis, one of the most common pathogens of maize worldwide. Wild-type strains of G. moniliformis produce predominantly four fumonisins (FB1, FB2, FB3 and FB4) that differ from each other by the presence or absence of hydroxyl groups at carbons 5 (C-5) and 10 of the polyketide-derived backbone. Here, we describe the role of the FUM9 gene in fumonisin biosynthesis in G. moniliformis. FUM9 is located in the fumonisin biosynthetic gene cluster (FUM) and is predicted to encode a dioxygenase. FUM9 deletion mutants only produce fumonisins that lack the C-5 hydroxyl group (FB3 and FB4). This is the same fumonisin production phenotype exhibited by previously described mutants of G. moniliformis with defective alleles at the meitotically defined Fum3 locus. Nucleotide sequence analysis of the FUM9 gene in one of these Fum3 mutants revealed a single C to T transition that introduces a stop codon in the coding region. Transformation of a wild-type FUM9 allele into the same Fum3 mutant restored wild-type fumonisin production. These results indicate that the FUM9 protein catalyzes C-5 hydroxylation during fumonisin biosynthesis. In addition, the results demonstrate that FUM9 and the Fum3 locus are the same gene. Because Fum3 was described first, we propose that FUM9 be renamed FUM3.