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Title: A GENETIC AND BIOCHEMICAL APPROACH TO STUDY TRICHOTHECENE DIVERSITY IN FUSARIUM SPOROTRICHIOIDES AND FUSARIUM GRAMINEARUM

Author
item Brown, Daren
item McCormick, Susan
item Alexander, Nancy
item Proctor, Robert
item Desjardins, Anne

Submitted to: Fungal Genetics and Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: The fungus Fusarium graminearum causes Fusarium Head Blight (in wheat) and corn ear rot resulting in the loss of billions of dollars in crops world-wide each year. Fusarium species synthesize a group of toxins called trichothecenes that are critical to causing disease. We are studying the genes involved in the biosynthesis of trichothecenes in order to identify strategies for reducing or eliminating fungal infection and trichothecene contamination in wheat and corn. In this study, we compared the nucleotide sequence in a cluster of 10 genes obtained from related Fusarium species that synthesize different types of trichothecenes. This comparative genomics strategy allowed us to provide new information on two genes likely involved in toxin synthesis and correlate differences in gene structure with differences in the type of trichothecenes the two species produce. Understanding how these toxins are made may allow us to devise new strategies to limit their synthesis, thereby reducing fungal disease of wheat and corn.

Technical Abstract: The trichothecenes T-2 toxin and deoxynivalenol (DON) are fungal natural products that are toxic to both animals and plants. Their importance in the pathogenicity of Fusarium spp. on crop plants has inspired efforts to understand the genetic and biochemical mechanisms leading to trichothecene synthesis. In order to better understand T-2 toxin biosynthesis by Fusarium sporotrichioides and DON biosynthesis by F. graminearum, we compared the nucleotide sequence of the 23-kb core trichothecene gene cluster from each organism. This comparative genomics allowed us to predict proteins encoded by two trichothecene genes, TRI9 and TRI10, that had not previously been described from either Fusarium species. Differences in gene structure were also correlated with differences in the types of trichothecenes the two species produce. Gene disruption experiments showed that F. sporotrichioides TRI7 (FsTRI7) is required for acetylation of the oxygen on C-4 of T-2 toxin. Sequence analysis indicated that F. graminearum TRI7 (FgTRI7) is non-functional. This is consistent with the fact that the FgTRI7 product is not required for DON synthesis in F. graminearum because C-4 is not oxygenated.