The oomycete response gene LURP1 is required for defense against Hyaloperonospora parasitica in Arabidopsis thaliana

LURP1 is a member of the LURP cluster and the PR1 regulon, two previously defined sets of co-expressed Arabidopsis thaliana genes that share a pronounced upregulation in response to infections by the pathogenic oomycete Hyaloperonospora parasitica. LURP1 shows the most extreme transcriptional inducibility by H. parasitica of all LURP and PR1 regulon genes. Using insertion mutants we found that LURP1 is required for full basal defense to H. parasitica and resistance to this pathogen mediated by the R-proteins RPP4 and RPP5. The LURP1 protein shows no obvious similarity to proteins of known molecular function. We identified a 39-bp region of the LURP1 promoter that mediates reporter gene expression in response to H. parasitica and salicylic acid. This promoter region contains a W box motif, W-LURP1, that interacts in vitro with nuclear factors producing two separate DNA-binding patterns. W-LURP1-related sequences are strongly enriched in the promoters of the PR1 regulon, suggesting a role for this motif in the coordinated expression of genes inducible by H. parasitica and related defense conditions.