Identification and characterization of regulatory genes involved in fumonisin biosynthesis by Fusarium verticillioides
Abstract
Fusarium verticillioides is ubiquitous and an important pathogen of maize. This fungus produces a potent class of mycotoxins called fumonisins, of which fumonisin B1 (FB1) is the most abundant in contaminated food products and animal feed. Differences in FB 1 production were found during fungal colonization of separated germ and degermed kernels. These differences correlated with pH changes in the tissues but not with fungal growth. To further explore the role of ambient pH on the physiology of the fungus, a pH-regulatory gene homologue, PAC1, was isolated. The characterization of a PAC1 disruption mutant indicated that the gene is necessary for growth at alkaline pH and repression of FB1 biosynthesis. In addition, a candidate regulatory gene, ZFR1, was identified in an EST library enriched for transcripts expressed by the fungus during FB1 biosynthesis. Transcription of ZFR1 was also correlated with FB1 production on colonized maize kernel fractions. ZFR1 is predicted to encode a protein containing a zinc binuclear cluster domain. Deletion mutants of ZFR1 in F. verticillioides are not impaired in growth or development on maize kernels, but they produced <10% of the FB1 produced by either wild type or rescued strains. This study provides new insight into the effect of microenvironment on fungal metabolism and reveals potential targets for controlling FB1 contamination of maize.
Degree
Ph.D.
Advisors
Woloshuk, Purdue University.
Subject Area
Plant pathology|Microbiology
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