Molecular Characterization of Erysiphe necator (powdery mildew) resistance loci from the grapevine cultivar `Regent´ and their signaling network

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The grapevine cultivar Regent carries resistance to Powdery Mildew on chromosome 15 at locus Ren3. In this locus four candidate genes were identified. These need to be characterized for their function to determine the gene that mediates resistance. Their transcripts will be investigated in detail (determination of start and end of RNA, splice variants). Encoded proteins will be studied in fusion with GFP (green fluorescent protein) in regard to their localization in the cell. All these experiments will be performed in comparison of E. necator inoculated and non-inoculated resistant and susceptible grapevine plants. An additional resistance locus Ren9 was found on chromosome 15. Its sequence needs to be analyzed for the genes encoded there. Subsequently, also these candidate genes have to be characterized for their function. The candidate resistance genes identified so far code for receptors sensing signaling molecules (effectors) released by powdery mildew according to their molecular structure. The interaction between receptor and effector mediates a hypersensitive response (a localized cell death around the infection site) as defense response. The network of signal transduction that triggers various defense pathways of the plant will be studied by a comprehensive RNA-Seq experiment comparing a susceptible grapevine cultivar to Regent. This experiment will deliver information on the majority of genes active at different time points following experimental inoculation with spores of powdery mildew or mock inoculation. Differentially active genes should enable to resolve the signaling pathways concerned. Key regulatory genes will be identified. They should be applicable to improve the breeders selection for durable resistance after tagging them with molecular markers for use in marker-assisted grapevine breeding.