EDM2 is required for RPP7-dependent disease resistance in Arabidopsis and affects RPP7 transcript levels

• Published in: The Plant journal : for cell and molecular biology 2007-03, Vol.49 (5), p.829-839
• Main Authors: Eulgem, Thomas, Tsuchiya, Tokuji, Wang, Xiao-Jun, Beasley, Britt, Cuzick, Alayne, Tör, Mahmut, Zhu, Tong, McDowell, John M, Holub, Eric, Dangl, Jeffery L
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Amino Acid Sequence; Arabidopsis - genetics; Arabidopsis - parasitology; Arabidopsis - physiology; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; Biological and medical sciences; Botany; Chromosomes, Plant; disease resistance gene; EDM2 (enhanced downy mildew 2)-like proteins (ELPs); Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Regulation, Plant; Genes, Plant; Genetics and breeding of economic plants; Homeodomain Proteins; Hyaloperonospora parasitica; Immunity, Innate; Molecular biology; Molecular Sequence Data; Multigene Family; Mutation; Oligonucleotide Array Sequence Analysis; Peronospora - physiology; Peronospora parasitica; Pest resistance; Plant Diseases - immunology; plant homeodomain (PHD) finger; Plant pathogens; Plant resistance; Sequence Alignment; Signal Transduction; Transcription Factors - metabolism; Transcription, Genetic; Varietal selection. Specialized plant breeding, plant breeding aims
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313X.2006.02999.x

Specific disease resistance of Arabidopsis thaliana against the Hyaloperonospora parasitica isolate Hiks1 (HpHiks1) is mediated by RPP7. Although this disease resistance gene encodes a typical nucleotide binding site leucine-rich repeat (NB-LRR) disease resistance protein, its function is independent of the defense hormone salicylic acid and most known genes required for plant immune responses. We identified EDM2 (enhanced downy mildew 2) in a genetic screen for RPP7 suppressors. Mutations of EDM2 phenocopy RPP7 mutations, but do not affect other tested disease resistance genes. We isolated EDM2 by map-based cloning. The predicted EDM2 protein is structurally unrelated to previously identified components of the plant immune system, bears typical features of transcriptional regulators, including plant homeodomain (PHD)-finger-like domains, and defines a plant-specific protein family. In edm2 mutants both constitutive and HpHiks1-induced RPP7 transcript levels are reduced, suggesting that EDM2 is either a direct or an indirect regulator of RPP7 expression. Microarray analyses defined a set of defense-associated genes, the expression of which is suppressed during successful HpHiks1 colonization of either rpp7 or edm2 plants. This transcriptional phenotype is counteracted by an EDM2/RPP7-dependent mechanism.