Genes, gene clusters, and biosynthesis of trichothecenes and fumonisins inFusarium

Trichothecenes and fumonisins are mycotoxins produced by Fusarium, a filamentous fungus that can cause disease in barley, maize, rice, wheat, and some other crop plants. Research on the genetics and biochemistry of trichothecene and fumonisin biosynthesis has provided important insights into the genetic and biochemical pathways in Fusarium that lead to formation of these mycotoxins. In Fusarium, trichothecene biosynthetic enzymes are encoded by genes at three loci: the single-gene TRI101 locus, the two-gene TRI1-TRI16 locus, and the 12-gene core TRI cluster. In contrast, fumonisin biosynthetic enzymes identified to date are all located at one locus, the 17-gene FUM cluster. The FUM and core TRI clusters also encode proteins that regulate expression of the cluster genes and proteins that are involved in mycotoxin transport across the cell membrane. Biosynthetic pathways for both mycotoxins have been proposed based on a combination of biochemical and genetic evidence, including toxin production phenotypes of Fusarium mutants in which individual TRI or FUM genes have been inactivated. Some TRI and FUM gene mutants have also been employed to examine the role of mycotoxin production in plant pathogenesis. The studies indicate that trichothecene production can contribute to the ability of F. graminearum to cause wheat head blight, one of the most important wheat diseases in the world. Thus, studies into the genetic basis of mycotoxin production have identified a potential target to enhance resistance of wheat to a major plant disease and mycotoxin contamination problem.