FUM13 encodes a short chain dehydrogenase/reductase required for C-3 carbonyl reduction during fumonisin biosynthesis in Gibberella moniliformis.
Fumonisins are polyketide-derived mycotoxins produced by the filamentous fungus Gibberella moniliformis (anamorph Fusarium verticillioides). Wild-type strains of the fungus produce predominantly four B-series fumonisins, designated FB(1), FB(2), FB(3), and FB(4). Recently, a cluster of 15 putative fumonisin biosynthetic genes (FUM) was described in G. moniliformis. We have now conducted a functional analysis of FUM13, a gene in the cluster that is predicted by amino acid sequence similarity to encode a short chain dehydrogenase/reductase (SDR). Mass spectrometric analysis of metabolites from FUM13 deletion mutants revealed that they produce approximately 10% of wild-type levels of B-series fumonisins as well as two previously uncharacterized compounds. NMR analysis revealed that the new compounds are similar in structure to FB(3) and FB(4) but that they have a carbonyl function rather than a hydroxyl function at carbon atom 3 (C-3). These results indicate that the FUM13 protein catalyzes the reduction of the C-3 carbonyl to a hydroxyl group and are the first biochemical evidence directly linking a FUM gene to a specific reaction during fumonisin biosynthesis. The production of low levels of FB(1), FB(2), FB(3), and FB(4), which have a C-3 hydroxyl, by the FUM13 mutants suggests that G. moniliformis has an additional C-3 carbonyl reductase activity but that this enzyme functions less efficiently than the FUM13 protein.
National Center for Agricultural Utilization Research, Agricultural Research Service, U.S. Department of Agriculture, 1815 North University Street, Peoria, IL 61604-3999, USA. butchkora@ncaur.usda.gov
Robert A E
RA
Butchko
Ronald D
RD
Plattner
Robert H
RH
Proctor
D000595:Amino Acid Sequence; D037341:Fumonisins / Q000378:metabolism*; D017353:Gene Deletion; D005874:Gibberella / Q000201:enzymology / Q000235:genetics*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics*; D016133:Polymerase Chain Reaction
D037341:Fumonisins; D010088:Oxidoreductases