Interception of the Fungal Haustorium by the Broad-Spectrum Plant Resistance Protein RPW8

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"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."Many fungal and fungus-like oomycete pathogens breach the plant cell wall and develop a feeding structure named the haustorium to steal photosynthate from the host cell. The haustorium is encased by an enigmatic extra-haustorial membrane (EHM) believed to be derived from the host cell plasma membrane. Although this interfacial membrane is of critical importance to the host for defense and the pathogen for pathogenesis, until recently not a single EHM-resident protein has been identified. Preliminary data from the PI's group now demonstrate that the broad-spectrum disease resistance protein RPW8.2 is specifically targeted to the EHM for defense against isolates of Golovinomyces spp. that cause wide-spread powdery mildew diseases. This project aims to characterize the structure-function relationships of RPW8.2 in relation to its defense and intracellular trafficking activities. The trafficking pathway of RPW8.2 from its site of synthesis to the EHM will be elucidated via pharmacological, biochemical and genetic approaches and the role of a 14-3-3 protein in this process will be determined. Through its analysis of RPW8.2-mediated broad-spectrum mildew resistance, this project will provide fresh insights into the molecular warfare between plants and pathogens. In particular, cellular mechanisms of targeted protein trafficking will be analyzed as an important component of host innate immunity. The basic mechanisms to be characterized in this project may open new avenues for engineering more effective, focused defense systems against numerous haustorium-forming fungal and oomycete pathogens, thereby leading to gains in crop production and environmental protection. Furthermore, the proposed project will integrate research with education by providing ideal hands-on training opportunities for high school internship students, undergraduates, graduates, and postdoctoral researchers in plant genetics and molecular plant pathology.