FUNGAL ENDOPHYTES OF MAIZE: GENE PRODUCTS CONFERRING RESISTANCE TO AFLATOXIN AND FUMONISIN
Location: Bacterial Foodborne Pathogens & Mycology Research Unit
Title: EXPRESSED SEQUENCE TAGS (ESTS), FUM CLUSTER TRANSCRIPTION FACTOR AND MICROARRAYS
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 4, 2006
Publication Date: August 4, 2006
Citation: Brown, D.W., Butchko, R.A., Busman, M., Proctor, R. 2006. Expressed sequence tags (ests), fum cluster transcription factor and microarrays [abstract]. The Institute for Genomic Research. Talk #1.
Fumonisins are a family of mycotoxins produced by the filamentous fungus Fusarium verticillioides that often contaminates maize around the globe. F. verticillioides is generally an endophyte of maize, but under some conditions, it can cause seedling disease and ear, root, and stalk rots, as well as synthesize fumonisins. Fumonisins are associated with several animal diseases, and linked with cancer in animals and humans. They are synthesized by a group of enzymes encoded by genes localized within a 42.5 kb portion of the F. verticillioides genome. The gene cluster includes 16 genes, of which none appear to play a regulatory role. Understanding fumonisin biosynthesis and its genetic regulation may lead to the development of novel methods to limit its synthesis, and eliminate fumonisins from the animal and human food chain. We, in collaboration with The Institute for Genomic Research (TIGR), have created an expressed sequence tag (EST) library containing over 87,000 sequences that correspond to 11,119 unique sequences. Our research program has two major goals; namely, to identify genes involved in regulating fumonisin biosynthesis, and to identify genes involved in pathogenicity. Transcripts corresponding to genes within the fumonisin gene cluster were found primarily in four of the eight libraries. Three of the four libraries also contained transcripts to a new gene (FUM21) located adjacent to the fumonisin polyketide synthase gene, FUM1. The predicted FUM21 protein includes a Zn(II)2Cys6 DNA binding domain, and a second domain also associated with fungal transcription factors. FUM21 deletion mutants ('FUM21) produce no fumonisin after 10 days, and 70% less fumonisin after 21 days growth on cracked corn, and accumulate significantly less FUM1 and FUM8 transcripts than wild type in a liquid medium. Over-expression of FUM21 restored fumonisin biosynthesis in a 'FUM21 strain. We are using microarrays representing the TIGR F. verticillioides Gene Index of 11,126 total unique sequences to examine expression of genes that may be involved in pathogenicity, and to explore whether FUM21 alternative splice forms (ASFs) play a role in regulating fumonisin biosynthesis.