Submitted to: National Fusarium Head Blight Forum Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 12/2/2007
Publication Date: 12/2/2007
Citation: Pasquali, M., Seong, K., Menke, J., Lysoe, E., Hilburn, K.L., Xu, J., Kistler, H.C. 2007. Spore Development and Trichothecene Mutants of Fusarium graminearum [abstract]. Proceedings of the National Fusarium Head Blight Forum. p. 32. Interpretive Summary:
Technical Abstract: To understand trichothecene accumulation and the infection cycle of the head blight pathogen F. graminearum sensu stricto, fungal gene expression profiles were monitored during germination of ascospores and during plant infection. A total of 328 genes were determined to be specifically expressed in ascospores. Among genes highly up-regulated in ascospores was one most closely related to FoStuA of F. oxysporum and StuA in Aspergillus. Mutants deleted for this gene in F. graminearum (FgStuA) are greatly decreased in sporulation and produce no perithecia. Unlike FoStuA mutants in F. oxysporum, FgStuA mutants are greatly reduced in pathogenicity. Reduced pathogenicity may be due to decreased levels of trichothecene toxins, which in the mutant are <1% the levels of wildtype. Levels of transcripts corresponding to Tri5, but not other genes involved trichothecene biosynthesis, were extremely diminished in the FgStuA mutant. Thus both sporulation and trichothecene synthesis may be regulated under the control of StuA. We are also developing isogenic lines of F. graminearum that differ only at the toxin biosynthesis cluster, in order to understand how DON and the chemical profile of trichothecene derivatives (trichothecene chemotype) influences fungal pathogenicity. The trichothecene biosynthetic gene cluster has been completely deleted from both a deoxynivalenol (DON) and a nivalenol producing strain of F. graminearum and will be replaced with the cluster from a different chemotype. Five separate genes from the cluster also have been individually deleted. Biological and regulatory characteristics of the mutant strains will be discussed.