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ARS Home » Midwest Area » West Lafayette, Indiana » Crop Production and Pest Control Research » Research » Publications at this Location » Publication #200715
Title: RAS2 regulates growth and pathogenesis in Fusarium graminearum

Author
item Bluhm, Burton
item ZHAO, X - PURDUE UNIV.
item FLAHERTY, J - COKER COLLEGE
item XU, J-R - PURDUE UNIV.
item Dunkle, Larry

Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2007
Publication Date: 6/4/2007
Citation: Bluhm, B., Zhao, X., Flaherty, J.E., Xu, J., Dunkle, L.D. 2007. RAS2 regulates growth and pathogenesis in Fusarium graminearum. Molecular Plant-Microbe Interactions. 2(6):627-636.

Interpretive Summary: Fusarium head blight (wheat scab) is a fungal disease of wheat and barley that accounts for millions of dollars lost in yield and grain quality, but the precise genetic and molecular mechanisms by which the fungus infects and causes damage are not defined. We discovered and defined the role of a gene in the pathogen that encodes a small GTP-binding protein that is important for a variety of vegetative and reproductive growth phenomena and for the ability of the fungus to cause severe head blight symptoms. The results presented contribute information that will be useful in establishing the genetic and molecular bases of pathogen virulence and provide clues to potential targets or weaknesses in the life cycle that can be exploited for effective disease management strategies. Such information will be important to plant pathologists and geneticists in selecting wheat germplasm and improving production practices that minimize damage caused by Fusarium head blight.

Technical Abstract: Fusarium graminearum is a ubiquitous pathogen of cereal crops including wheat, barley, and maize. Diseases caused by F. graminearum are of particular concern because harvested grains are frequently contaminated with harmful mycotoxins such as deoxynivalenol (DON). Currently, little is known about molecular mechanisms regulating plant infection and mycotoxin biosynthesis in this important pathogen. In this study, we characterized a gene (RAS2) encoding a Ras GTPase in F. graminearum and determined its role in fungal development and pathogenesis. The predicted protein encoded by RAS2 was similar to Ras GTPases from a broad range of eukaryotic species. Expression of RAS2 was induced under conditions of nitrogen limitation but not during infection of barley. The ras2 deletion mutant was viable but grew slower than wild type on solid media. Additionally, the ras2 mutant was significantly reduced in its ability to infect wheat heads and corn silks despite being able to produce DON in wheat and maize kernels. Although intracellular cAMP levels were not affected by deletion of RAS2, activation of the MAP kinase Gpmk1 was significantly reduced in the ras2 mutant. These data indicate that RAS2 regulates growth and virulence in F. graminearum at least in part through the activation of the Gpmk1 MAP kinase pathway.