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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 #307095
Title: Variation in the fumonisin biosynthetic gene cluster in fumonisin-producing and nonproducing black aspergilli

Author
item SUSCA, ANTONIA - National Research Council - Italy
item Proctor, Robert
item BUTCHKO, ROBERT - Former ARS Employee
item HAIDUKOWSKI, MIRIAM - National Research Council - Italy
item STEA, GAETANO - National Research Council - Italy
item LOGRIECO, ANTONIO - National Research Council - Italy
item MORETTI, ANTONIO - National Research Council - Italy

Submitted to: Fungal Genetics and Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2014
Publication Date: 12/1/2014
Citation: Susca, A., Proctor, R., Butchko, R.A.E., Haidukowski, M., Stea, G., Logrieco, A., Moretti, A. 2014. Variation in the fumonisin biosynthetic gene cluster in fumonisin-producing and nonproducing black aspergilli. Fungal Genetics and Biology. 73:39-52.

Interpretive Summary: Mycotoxins are toxic metabolites produced by fungi and are a health risk to humans and domestic animals, because they can contaminate food and feed crops. Fumonisins are mycotoxins that can contaminate corn, figs, green onion, raisins, wine, and grape juice used to make wine. Production of fumonisin mycotoxins by the fungi Aspergillus niger and Aspergillus welwitschiae is of concern because these species frequently occur on grapes. Previous studies indicate that within each species, some individuals (strains) produce fumonisins and others do not. The goal of the current study was to identify genetic differences between fumonisin-producing and nonproducing strains that could account for nonproduction. In fungi, genes responsible for making fumonisins are located next to one another in a region called the fumonisin biosynthetic gene (fum) cluster. Our analyses revealed that most of the fum cluster has been lost in fumonisin-nonproducing strains of A. welwitschiae, and such loss could be the direct cause of the inability to produce fumonisins. In contrast, all fum cluster genes are present in fumonisin-nonproducing strains of A. niger. But, there are small changes in the DNA sequence of individual fum cluster genes that could affect the ability to produce fumonisins. Examination of four other Aspergillus species revealed that they have also lost most of the fum cluster. This suggests that the cluster and perhaps the ability to produce fumonisins were once more wide spread among Aspergillus species than they currently are. In addition, these data facilitate the development of simple genetic tests to rapidly evaluate the fumonisin producing potential of individual strains. This study expands understanding of the genetic mechanisms responsible for the diversity and distribution of mycotoxin production in fungi. The results will be of use to academic, government and industrial organizations working to develop methods that limit mycotoxin contamination in crops.

Technical Abstract: The ability to produce fumonisin mycotoxins varies among members of the black aspergilli. Previously, analyses of selected genes in the fumonisin biosynthetic gene (fum) cluster in black aspergilli from California grapes indicated that fumonisin-nonproducing isolates of Aspergillus welwitschiae lack six fum genes, but nonproducing isolates of A. niger do not. In the current study, analyses of black aspergilli from grapes from the Mediterranean Basin indicate that the genomic context of the fum cluster is the same in isolates of A. niger and A. welwitschiae regardless of fumonisin-production ability and that full-length clusters occur in producing isolates of both species and nonproducing isolates of A. niger. In contrast, the cluster has undergone an eight-gene deletion in fumonisin-nonproducing isolates of A. welwitschiae. Phylogenetic analyses suggest each species consists of a mixed population of fumonisin-producing and nonproducing individuals, and that existence of both production phenotypes may provide a selective advantage to these species. Differences in gene content of fum cluster homologues and phylogenetic relationships of fum genes suggest that the genetic lesion(s) responsible for the nonproduction phenotype differs, and therefore arose independently, in the two species. Partial fum cluster homologues were also identified in genome sequences of four other black Aspergillus species. Gene content of these partial clusters and phylogenetic relationships of fum sequences indicate that non-random partial deletion of the cluster has occurred multiple times among the species. This in turn suggests that an intact cluster and fumonisin production were once more widespread among black aspergilli.