Phylogenomic and functional domain analysis of polyketide synthases in Fusarium

Authors: Brown, Daren; Butchko, Robert; BAKER, SCOTT - Pacific Northwest National Laboratory; Proctor, Robert

Submitted to: Fungal Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2011
Publication Date: 12/19/2011
Citation: Brown, D.W., Butchko, R.A., Baker, S.E., Proctor, R. 2011. Phylogenomic and functional domain analysis of polyketide synthases in Fusarium. Fungal Biology. 116(2):318-331.

Interpretive Summary: Fusarium species cause a range of plant diseases and produce a variety of fungal toxins (mycotoxins) that can contaminate human and animal foods. Identification of the genes responsible for the production of polyketides, the largest family of mycotoxins, has advanced efforts to understand their role in interactions between the fungus and plant hosts, and is critical to developing novel strategies to limit toxin contamination of grain. Previously, we identified the entire family of genes responsible for synthesizing polyketides in four different Fusarium species. In the current study, we demonstrated that they are functional, and predicted the functions of several of these genes based on their relationships to previously characterized members of this gene family. This research provides a foundation for understanding the function of these mycotoxin associated genes and will be of use to plant pathologists, plant breeders, and other scientists involved in the development of new ways to limit mycotoxin contamination of grain.

Technical Abstract: Fusarium species are ubiquitous in nature, cause a range of plant diseases, and produce a variety of chemicals often refered to as secondary metabolites. Although some fungal secondary metabolites affect plant growth or protect plants from other fungi and bacteria, their presence in grain based food and feed is more often associated with a variety of diseases in plants and in animals. Many of these structurally diverse metabolites are derived from a family of related enzymes called polyketide synthases (PKSs). A search of genomic sequence of Fusarium verticillioides, F. graminearum, F. oxysporum, and Nectria haematococca (anamorph F. solani) identified a total of 58 PKS genes. To gain insight into how this gene family evolved and to guide future studies, we conducted a phylogenomic and functional domain analysis. The resulting geneaology suggested that Fusarium PKSs represent 34 different groups responsible for the synthesis of different core metabolites. The variation in the Fusarium PKS gene family is due to gene duplication and loss events as well as enzyme gain-of-function due to the acquisition of new domains or of loss-of-function due to nucleotide mutations. Transcriptional analysis indicate that the 16 F. verticillioides PKS genes are expressed under a range of conditions, further evidence that they are functional genes that confer the ability to produce secondary metabolites.