Isolation and functional characterisation of a cluster of TIR-NBS-LRR genes linked to powdery mildew resistance in grapevine

• Published in: Phytopathology Vol. 98; no. 6; p. S13
• Main Authors: Anderson, C, Feechan, A, Jermakow, A M, Bouquet, A, Adam-Blondon, A, Thomas, M R, Dry, IB
• Format: Journal Article
• Language: English
• Published: 01.06.2008
• Subjects: Erysiphe necator; Hordeum vulgare; Uncinula necator; Vitaceae
• ISSN: 0031-949X

Grapevine powdery mildew, caused by Erysiphe necator (syn. Uncinula necator), is an economically important fungal disease of grapevines worldwide causing reduced yield and loss of quality. The North American grapevine Muscadinia rotundifolia is completely resistant to powdery mildew due to the action of a single dominant locus designated Run1. Phenotypically, Run1 mediated resistance resembles that conferred by the barley powdery mildew resistance gene, Mla12, inducing a hypersensitive response, within infected epidermal cells, following fungal haustorium formation. The Run1 locus was introgressed into V. vinifera by successive back-crosses generating segregating populations that were used in genetic and physical mapping studies. Run1 resistance has been localised to a region containing a cluster of eleven closely related resistance gene analogs (RGAs) encoding both full-length and truncated TIR-NBS-LRR proteins. Real-time expression analysis indicates differential expression of these RGA candidates in response to powdery mildew infection. Full-length (11-15 kb) genomic cassettes containing RGA candidates with native promoter and terminator sequences were agroinfiltrated into tobacco and confirmed to be transcriptionally active. Interestingly, one RGA candidate was found to be auto-active in tobacco causing necrotic lesions to form after 3-4 days. Analysis of the translated protein product of this RGA gene indicates it to have a deletion within the C-terminal domain compared to the other RGA genes suggesting that this region may be important for repression of wild-type RGA activity.