Submitted to: ARS Workshop on Fusarium Toxins Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: September 17, 1997
Publication Date: N/A
Technical Abstract: Gibberella fujikuroi mating population A is a major pathogen of maize and produces a family of toxins known as fumonisins that are associated with a number of mycotoxicoses. Our multidisciplinary research team is using a variety of classical meiotic and molecular genetic methods to identify fumonisin biosynthetic genes. UV mutagenesis yielded a strain (uv26) that appeared to be lacking the ability to hydroxylate fumonisins at carbon number 5 (C-5). Mutant uv26 produced fumonisin B3, but did not produce fumonisins B2 or B1, both of which have a C-5 hydroxyl group. Classical genetic analysis indicated that the uv26 mutation segregates as a single locus and is tightly linked to the fum1, fum2 and fum3 loci previously identified in natural variants, and to the RAPD markers OPA16 and OPH3, on chromosome 1 of G. fujikuroi. In addition, fum3 and the uv26 mutation may be allelic because both confer the same fumonisin phenotype and no recombinant progeny were recovered from a cross between strains carrying these two markers. Efforts are in progress to complement the uv26 mutation by transformation with cosmid libraries constructed with DNA from wild-type strains of G. fujikuroi. To date, more than 1700 hygromycin-resistant transformants of the uv26 mutant have been analyzed, but no fumonisin-producing complemented strains have been identified. Efforts are also in progress to isolate fumonisin biosynthetic genes by identifying genes that are differentially expressed during fumonisin production, and by designing PCR-primers in order to amplify putative polyketide synthase genes that may be involved in fumonisin biosynthesis.