Ancestral Polymorphism and Adaptive Evolution in the Trichothecene Mycotoxin Gene Cluster of Phytopathogenic Fusarium

Filamentous fungi within the Fusarium graminearum species complex (Fg complex) are the primary etiological agents of Fusarium head blight (scab) of wheat and barley. Scab is an economically devastating plant disease that greatly limits grain yield and quality. In addition, scabby grain is often cont...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2002-07, Vol.99 (14), p.9278-9283
Main Authors: Ward, Todd J., Bielawski, Joseph P., Kistler, H. Corby, Sullivan, Eileen, O'Donnell, Kerry
Format: Article
Language:English
Subjects:
Biological Sciences
Biological taxonomies
Disease
DNA, Fungal - genetics
Evolution
Evolution, Molecular
Flowers & plants
Fusarium
Fusarium - genetics
Gene Silencing
Genes
Genes, Fungal
Genetic variation
Molecular Sequence Data
Multigene Family
Mycotoxins
Parsimony
Pathogens
Phylogenetics
Phylogeny
Plants
Polymorphism, Genetic
Recombination, Genetic
Trichothecenes
Trichothecenes - genetics
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Summary:Filamentous fungi within the Fusarium graminearum species complex (Fg complex) are the primary etiological agents of Fusarium head blight (scab) of wheat and barley. Scab is an economically devastating plant disease that greatly limits grain yield and quality. In addition, scabby grain is often contaminated with trichothecene mycotoxins that act as virulence factors on some hosts, and pose a serious threat to animal health and food safety. Strain-specific differences in trichothecene metabolite profiles (chemotypes) are not well correlated with the Fg complex phylogeny based on genealogical concordance at six single-copy nuclear genes. To examine the basis for this discord between species and toxin evolution, a 19-kb region of the trichothecene gene cluster was sequenced in 39 strains chosen to represent the global genetic diversity of species in the Fg complex and four related species of Fusarium. Phylogenetic analyses demonstrated that polymorphism within these virulence-associated genes is transspecific and appears to have been maintained by balancing selection acting on chemotype differences that originated in the ancestor of this important group of plant pathogens. Chemotype-specific differences in selective constraint and evidence of adaptive evolution within trichothecene genes are also reported.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.142307199