Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/2004
Publication Date: 12/6/2004
Citation: Vogel, J.P., Raab, T.K., Somerville, S.C. 2004. Mutations in pmr5 result in powdery mildew resistance and altered cell wall composition. Plant Journal. 40:968-978. Interpretive Summary: This paper describes the identification and characterization of a plant mutant, pmr5, that is highly resistant to powdery mildew disease. Importantly, the disease resistance exhibited by pmr5 plants does not require known plant defense pathways indicating that a novel form of disease resistance is responsible for pmr5-mediated resistance. The composition of pmr5 cell walls was examined because pmr5 plants look very similar to a previously described mutant, pmr6, that was shown to affect cell wall composition. Like pmr6, pmr5 cell walls were found to contain more pectin. The gene corresponding to PMR5 was cloned. Database searches with the predicted protein sequence indicated that PMR5 belongs to a large family of plant-specific proteins of unknown function.
Technical Abstract: The complex relationship between plants and powdery mildew fungi suggests that host genes may be required for a compatible interaction. Previously, we described an Arabidopsis mutant, pmr6, which is resistant to powdery mildew independent of the activation of known host defense pathways. Thus, PMR6 is a candidate for a gene required by the pathogen during a compatible interaction. This paper describes the cloning and characterization of another gene required for powdery mildew susceptibility, PMR5. PMR5 belongs to a large family of plant-specific genes of unknown function. By all measures, pmr5 mutants are very similar to pmr6 mutants. Like pmr6, pmr5-mediated resistance does not require signaling through either the salicylic acid or ethylene/jasmonic acid defense pathways. Also, like pmr6, pmr5 cell walls are enriched in pectin. We speculate that pmr5 and pmr6 employ the same resistance mechanism.