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United States Department of Agriculture

Agricultural Research Service

Title: Screening of Fungal Species for Fumonisin Production and Fumonisin-Like Disruption of Sphingolipid Biosynthesis

Authors
item Norred, William
item Bacon, Charles
item Riley, Ronald
item Voss, Kenneth
item Meredith, Filmore

Submitted to: Mycopathologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 25, 1999
Publication Date: N/A

Interpretive Summary: There are many molds (fungi) that can grow on agricultural crops, causing plant diseases and producing poisons that can sicken animals or people. Several members of the fusaria group of fungi can produce toxins known as fumonisins. These toxins are frequent contaminants of corn, and there is much concern about how to prevent fumonisins from entering the food supply. .We previously developed a bioassay for fumonisins, which is a method to detect their presence in corn by looking for a particular type of response of cells or tissue slices to fumonisin exposure. This bioassay can be used in conjunction with chemical analysis to determine if fumonisins are present. In this study we used both the bioassay and chemical assay to screen a variety of fusaria and nonfusaria fungi for the presence of toxins with fumonisin-like activity. Most of the fungi were negative, but several did produce fumonisins and were positive in the bioassay. More research is sneeded to determine whether other fungi can produce similar biologically active compounds.

Technical Abstract: Fumonisins are mycotoxins produced by several species of Fusaria. They are found on corn and in corn-based products, can cause fatal illnesses in some animals and are suspected human esophageal carcinogens. Fumonisins are believed to cause toxicity by blocking ceramide synthase, a key enzyme in sphingolipid biochemistry which converts sphinganine (or sphingosine) and fatty acyl CoA to ceramide. Relatively few fungal species have been evaluated for their ability to produce fumonisins. Fewer have been studied to determine if they produced ceramide synthase inhibitors, whether fumonisin-like structures or not, therefore potentially having toxicity similar to fumonisins. We analyzed corn cultures of 49 isolates representing 32 diverse species of fungi for their ability to produce fumonisins. We also evaluated the culture extracts for ceramide synthase activity. Only cultures prepared with species reported previously to produce fumonisins - Fusarium moniliforme and F. proliferatum - tested positive for fumonisins. Extracts of these cultures inhibited ceramide synthase, as expected. None of the other fungal isolates we examined produced fumonisins or other compounds capable of inhibiting ceramide synthase. Although the fungi we selected for these studies represent only a handful out of the thousands of species that exist, they share the commonality that they are frequently associated with cereal grasses, including corn, either as pathogens or as asymptomatic endophytes. Thus, these results should be encouraging to those attempting to find ways to genetically manipulate fumonisin-producing fungi, to make corn more resistant, or to develop biocontrol measures because it appears that only a relatively few fungal contaminants of corn can produce fumonisins.

Last Modified: 12/21/2014