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ARS Home » Midwest Area » Peoria, Illinois » National Center for Agricultural Utilization Research » Mycotoxin Prevention and Applied Microbiology Research » Research » Publications at this Location » Publication #244651

Title: Tricarballylic ester formation during biosynthesis of fumonisin mycotoxins in Fusarium verticillioides

item LI, YAOYAO - Shandong University
item LOU, LILI - University Of Nebraska
item CERNY, RONALD - University Of Nebraska
item Butchko, Robert
item Proctor, Robert
item DU, LIANGCHENG - University Of Nebraska
item SHEN, YUEMAO - Shandong University

Submitted to: Mycology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/8/2013
Publication Date: 1/2/2014
Citation: Li, Y., Lou, L., Cerny, R.L., Butchko, R.A., Proctor, R., Du, L., Shen, Y. 2014. Tricarballylic ester formation during biosynthesis of fumonisin mycotoxins in Fusarium verticillioides. Mycology. 4(4):179-186.

Interpretive Summary: Understanding the biology and chemistry required for fumonisin biosynthesis by the fungal corn pathogen, Fusarium verticillioides, will aid in efforts to reduce or eliminate toxin contaminated grains from entering the food chain. Fumonisins are toxins produced by the fungus and can cause disease in animals and humans. Experiments described in this manuscript add to the understanding of the biological events and conditions that allow the fungus, F. verticillioides, to produce fumonisins. There are many steps in the biochemical pathway leading to the production of fumonisin, and each one can be considered a potential target for stopping the production of fumonisin. Here, one portion of the biosynthetic pathway is described with regard to the specific reaction mediated by a specific enzyme in the pathway as well as to the specific nature of the chemical building block required for biosynthesis of fumonisin. The identification of the chemical building block and its role in the biosynthetic pathway might lead to novel methods of eliminating or reducing fumonisin contamination of corn.

Technical Abstract: Fumonisins are polyketide-derived mycotoxins produced by Fusarium verticillioides, a widespread fungal pathogen of corn, and a common contaminant of corn-based food and feeds. Fumonisins contain two tricarballylic esters that are rare structural features in natural products. Here, we expressed three F. verticillioides genes, FUM7, FUM10, and FUM14, in E. coli and used the purified enzymes to investigate the esterification of the fumonisin polyketide backbone. When Fum7p was incubated in the presence of NADPH and Fe2+ with fumonisin analogs containing tetradehydro tricarballylic esters (DH4-FB) that were isolated from the FUM7-deleted mutant, no fumonisin was produced. Instead, new fumonisin analogs containing two oxalosuccinate esters, two isocitrate esters, or one oxalosuccinate ester and one isocitrate ester were detected. When the three enzymes were incubated with hydrolyzed FB3, a fumonisin precursor lacking the tricarballylic esters, isocitric acid, ATP, and NADPH, the tricarballylic esters-containing FB3 was observed. The esterified product was also detected when aconitic acid or tricarballylic acid was used. These data provide direct evidence for the role of FUM10, FUM14, and FUM7 in the biosynthesis of the rare tricarballylic esters. The results suggest that multiple intermediates in the Citric Acid Cycle could be involved in the ester side-chain formation of fumonisins.