Submitted to: Mycological Society of America
Publication Type: Abstract Only
Publication Acceptance Date: 8/9/2008
Publication Date: 8/9/2008
Citation: Lysoe, E., Pasquali, M., Breakspear, A., Kistler, H.C. 2008. The Transcription Factor FgStuA Influences Spore Development, Pathogenicity and Secondary Metabolism in the Plant Pathogenic Fungus Fusarium graminearum. Mycological Society of America. 59(4):43.
Technical Abstract: The filamentous fungus Fusarium graminearum causes extensive losses on cereals world-wide and contaminates harvested grain with mycotoxins, whose levels in the food supply are strictly regulated. We deleted the FgStuA gene in Fusarium graminearum and demonstrate its involvement in several different processes, such as spore development, pathogenicity and secondary metabolism. The FgStuA protein is a members of the APSES family which regulate morphogenesis and virulence in ascomycetes. FgStuA is closely related to FoStuA in F. oxysporum and StuA in Aspergillus, but unlike FoStuA mutants, the FgStuA mutants were greatly reduced in pathogenicity both on wheat and apple slices. Reduced pathogenicity may be due to decreased levels of trichothecene mycotoxins (<1% the levels of wildtype), which have shown to be pathogencity factors in wheat. Microarray analysis of the FgStuA mutant during plant infection shows that the trichothecene biosynthetic pathway is completely turned off. FgStuA mutants also were greatly reduced in asexual sporulation and produced no perithecia. The asexual spores produced also showed a slower germination than the wild-type, as well as reduced growth on agar plates. Microarray analysis during “sporulation conditions”, (when the wildtype produced asexual spores and the mutant produced no spores), showed that genes encoding several groups of cell-wall related proteins such as chitinases, glycanases and GPIs, mostly were down-regulated in the mutant. Other putative spore-related genes, such as hydrophobins, also were highly down-regulated in the mutant. Genes found in the MIPS functional categories Transcription, Protein synthesis and Proteins with binding functions were extremely up-regulated in the FgStuA mutant during sporulation conditions, similar to wildtype developmental time-points during conidia- and ascospore germination. On V8 agar, the FgStuA mutant has a white phenotype compared to the red wild-type. Under sporulation conditions, 17 contiguous genes, including all known genes for biosynthesis of the red pigment aurofusarin, were virtually turned off in the mutant. Also eight contiguous genes encoding a putative PKS-NPS hybrid, where found to be down-regulated. We conclude that the FgStuA protein in F. graminearum functions as a global regulator conferring cross pathway control of sporulation, pathogenicity and gene clusters important for secondary metabolism.