Submitted to: Journal of Agriculture and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/20/2010
Publication Date: 8/25/2010
Citation: Susca, A., Proctor, R., Mule, G., Stea, G., Ritieni, A., Logrieco, A., Moretti, A. 2010. Correlation of Mycotoxin Fumonisin B2 Production and Presence of the Fumonisin Biosynthetic Gene fum8 in Aspergillus niger from Grape. Journal of Agriculture and Food Chemistry. 58(16):9266-9272. Interpretive Summary: The results of this research provide an explanation for the sporadic contamination of grapes and grape juice with toxins known as fumonisins. These toxins have been reported as frequent contaminants of corn kernels for over two decades, but only recently have been found in grape and grape juice. While most samples do not contain fumonisins, investigations revealed that a common grape-associated fungus, Aspergillus niger, can produce fumonisins and that it is most likely responsible for fumonisin contamination of grapes/grape juice. In this study, we correlated fumonisin production in A. niger with the presence of a gene, fum8, that is the blue print for an enzyme that the fungus requires to produce fumonisins. Of the 32 strains of A. niger examined, about one third produced fumonisins and had fum8, whereas about two thirds did not produce the toxins and did not have fum8. These results indicate that lack of fumonisin production in A. niger strains most often results from absence in the fungus of at least one of the genes required for fumonisin production. This study provides a possible explanation for why fumonisin contamination of grapes/grape juice occurs at a relatively low frequency, even though A. niger is frequently present on grapes, and may allow for improved methods of fumonisin control.
Technical Abstract: Fumonisins are mycotoxins associated with cancer and several other serious diseases in humans and animals. Production of the mycotoxins has been reported for over two decades in Fusarium species, but has been reported only recently in strains of Aspergillus niger. In addition, a homologue of the fumonisin biosynthetic gene (FUM) cluster, originally identified in Fusarium verticillioides, has been identified in the genome sequence of A. niger. Here, we examined seven species in Aspergillus Section Nigri that occur on grapes for fumonisin production and presence of the fumonisin biosynthetic gene fum8, which served as a marker for the FUM cluster. Fumonisin B2 (FB2) production was detected in nine of 32 A. niger strains examined, but not in any strains of A. brasiliensis, A. carbonarius, A. foetidus, A. japonicus, A. tubingensis, and A. uvarum that were examined. In addition, PCR and Southern blot analyses provided evidence for the presence of fum8 in 11 A. niger strains but not in strains of the other species examined. These findings indicate that the discontinuity of fumonisin production in grape isolates of A. niger likely results from absence in some isolates of at least part of the FUM cluster. The results also confirm the taxonomic complexity of A. niger from grapes and provide a possible explanation for previously observed variability in FB2 contamination of grapes and wine.