Submitted to: Aflatoxin Workshop
Publication Type: Abstract Only
Publication Acceptance Date: 10/15/2003
Publication Date: 10/15/2003
Citation: Proctor, R., Brown, D.W., Seo, J., Lee, Y., Plattner, R.D. 2003. Discontinuous distribution of fumonisin biosynthetic genes in the gibberella fujikuroi species complex. Aflatoxin Workshop. Interpretive Summary:
Technical Abstract: Fumonisins are carcinogenic mycotoxins that frequently contaminate maize. Most studies on fumonisin production have focused on Fusarium verticillioides because of the wide spread occurrence of this fungus on maize. However, production has also been reported in several other Fusarium species in the Gibberella fujikuroi (Gf) complex and in F. oxysporum. The Gf complex consists of at least 29 closely related Fusarium species and includes several important plant pathogens and mycotoxin producers, including F. circinantum, F. proliferatum and F. subglutinans. Recently, a fumonisin biosynthetic gene (FUM) cluster was identified in F. verticillioides. In the current study, we surveyed 27 species of Fusarium for the presence of four FUM cluster genes and for fumonisin production. Strains of each species were subjected to Southern blot analysis with hybridization probes prepared from fragments of the FUM1, FUM8, FUM12 and FUM19 genes. These four genes are distributed across the entire length of the FUM cluster and they all function in fumonisin biosynthesis. Among species within the Gf complex, FUM genes were detected only in F. anthophilum, F. fujikuroi, F. globosum, F. proliferatum, F. nygamai, and F. verticillioides. These six species include at least one member of each of the three major clades delineated by O'Donnell et al. in the Gf complex. Fumonisin production was also detected in these same species except for F. anthophilum. Among the species outside the Gf complex, FUM genes and fumonisin production were detected only in F. oxysporum strain O-1890. We also conducted a phylogenetic analysis using nucleotide sequences from the FUM1 and FUM8 coding regions from the 7 species with the genes. The relationship inferred from this analysis were similar to those inferred from previous analyses of the Gf complex that used the 28S rDNA, mitochodrial small subunit rDNA and beta-tubulin genes. However, unlike the previous analyses the FUM1/FUM8 analysis indicated that species in the Asian and American clades of the complex were more closely related to one another than either was to the African clade. The analyses by O'Donnell et al. indicate that the Asian and African clades are more closely related to each other than either is to the American clade. The results of this study indicate that FUM genes are discontinuously distributed in the Gf complex. The detection of FUM genes only in species known to produce fumonisins indicates the inability of some species within the Gf complex to produce fumonisins results from the absence of FUM genes rather than the presence of genes that are either not functional or not expressed. Similarities in phylogenetic relationships inferred from FUM1/FUM8 and previous analyses suggests that the discontinuous distribution of FUM genes in the Gf complex arose, at least in part, via differential inheritance of the genes as species evolved. The presence of FUM genes in only 7 of the 27 species examined suggests that the potential to produce fumonisins is limited to relatively few species.