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Title: Identification of a 12-gene fusaric acid biosynthetic gene cluster in Fusarium species through comparative and functional genomics

item Brown, Daren
item LEE, SEUNG-HO - Rural Development Administration - Korea
item KIM, LEE-HAN - Rural Development Administration - Korea
item RYU, JAE-GEE - Rural Development Administration - Korea
item LEE, SOOHYUNG - Rural Development Administration - Korea
item SEO, YUNHEE - Seoul National University
item KIM, YOUNG HO - Seoul National University
item Busman, Mark
item YUN, SUNG-HWAN - Soonchunhyang University
item Proctor, Robert
item LEE, THERESA - Rural Development Administration - Korea

Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/24/2015
Publication Date: 3/1/2015
Publication URL:
Citation: Brown, D.W., Lee, S., Kim, L., Ryu, J., Lee, S., Seo, Y., Kim, Y., Busman, M., Yun, S., Proctor, R., Lee, T. 2015. Identification of a 12-gene fusaric acid biosynthetic gene cluster in Fusarium species through comparative and functional genomics. Molecular Plant-Microbe Interactions. 28(3):319-332.

Interpretive Summary: Some fungi that infect plants and cause crop diseases produce toxic metabolites (mycotoxins) that accumulate in food and feed crops and thereby pose health risks to humans and domestic animals. In fungi, genes that are directly required for synthesis of a mycotoxin are typically located adjacent to one another along a chromosome in what is known as a biosynthetic gene cluster. Multiple species of the fungus Fusarium produce the mycotoxin fusaric acid, which is also toxic to plants and is associated with plant disease symptoms caused by F. oxysporum. In the current study, we identified seven adjacent genes that are involved in synthesis of fusaric acid in F. oxysporum and F. verticillioides, a pathogen of maize with a worldwide distribution. We showed that the seven genes are located on a chromosome near five previously identified genes that are involved in fusaric acid production. These findings indicate that the fusaric acid biosynthetic gene cluster consists of 12 genes rather than five, as proposed previously. We also show that fusaric acid production is not required by either species of Fusarium to cause disease on its respective host species. This research will be of use to plant pathologists, plant breeders, and other scientists involved in i) identification of fungal species responsible for mycotoxin contamination problems and ii) development of new strategies to limit mycotoxin contamination in crop plants.

Technical Abstract: In fungi, genes involved in biosynthesis of a secondary metabolite (SM) are often located adjacent to one another in the genome and are coordinately regulated. These SM biosynthetic gene clusters typically encode enzymes, one or more transcription factors, and a transport protein. Fusaric acid is a polyketide-derived SM produced by multiple species of the fungal genus Fusarium. This SM is of concern because it is toxic to animals and, therefore, is considered a mycotoxin and may contribute to plant pathogenesis. Preliminary descriptions of the fusaric acid (FA) biosynthetic gene (FUB) cluster have been reported in two Fusarium species, the maize pathogen F. verticillioides and the rice pathogen F. fujikuroi. The cluster consisted of five genes and did not include a transcription factor or transporter gene. Here, analysis of the FUB region in F. verticillioides, F. fujikuroi, and F. oxysporum, a plant pathogen with multiple hosts, indicates the FUB cluster consists of at least 12 genes (FUB1 to FUB12). Deletion analysis confirmed that nine FUB genes, including two Zn(II)2Cys6 transcription factor genes, are required for production of wild-type levels of FA. Comparisons of FUB cluster homologs across multiple Fusarium isolates and species revealed insertion of non-FUB genes at one or two locations in some homologs. Although the ability to produce FA contributed to the phytotoxicity of F. oxysporum culture extracts, lack of production did not affect virulence of F. oxysporum on cactus or F. verticillioides on maize seedlings. These findings provide new insights into the genetic and biochemical processes required for FA production.