Submitted to: Molecular Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2009
Publication Date: 2/1/2010
Citation: Proctor, R.H., McCormick, S.P., Alexander, N.J., Desjardins, A.E. 2009. Evidence that a Secondary Metabolic Biosynthetic Gene Cluster has Grown by Gene Relocation During Evolution of the Filamentous Fungus Fusarium. Molecular Microbiology. 74(5):1128-1142. Interpretive Summary: The results of this research demonstrate the diversity of arrangement of genes involved in production of toxic compounds known as trichothecenes in the agriculturally important fungus Fusarium. Species of this fungus are among the most economically important fungal pathogens of crop plants because they infect many different crops all over the world, they can reduce crop yield and quality, and they can produce toxins (mycotoxins) that are hazards to human and animal health. Here, we compared the arrangement of genes that are involved in the production of a group of mycotoxins known as trichothecenes. The results demonstrate that some of the genes have been rearranged, others have been lost, others rendered nonfunctional by insertions or deletions into their DNA sequences, and others have moved to different positions on the same or different chromosomes. These findings provide tools for detection of different species of Fusarium. Such tools will aid in the monitoring of Fusarium in crop fields and at grain elevators and should provide a means to predict which types of trichothecene toxins different strains of the fungus are able to produce.
Technical Abstract: Trichothecenes are terpene-derived secondary metabolites produced by multiple genera of filamentous fungi, including many plant pathogenic species of Fusarium. These metabolites are of medical and agricultural interest because they are toxic to animals and plants and can contribute to pathogenesis of Fusarium on some crop species. Fusarium graminearum and F. sporotrichioides have a trichothecene biosynthetic gene (TRI) cluster that consists of 12 genes and two smaller loci that consist of one or two genes. Here, comparisons of additional Fusarium species have provided evidence that the TRI loci have had a complex evolutionary history that has included gene loss, nonfunctionalization and rearrangement as well trans-species polymorphism. The results also indicate that the TRI cluster has expanded in some species by relocation of two genes, TRI1 and TRI101, from the smaller loci into the cluster. Thus, evolutionary forces have driven consolidation of TRI genes into fewer loci in some fusaria but have maintained three distinct TRI loci in others.