9723493 Glazebrook Technical section Mutants of Arabidopsis thaliana with a phenotype of enhanced disease susceptibility (eds) were isolated and some were identified as alleles of NPR1 and others as alleles of PAD genes. NPR1 genes are known to be involved in the regulation of systematic acquired resistance and the PAD genes in the phytoalexin synthesis, a known defense response. In addition the EDS4 gene controls expression of the defense genes PR1 and PR5 in response to infection by a bacterial pathogen. Thus, the eds mutations define genes with important roles in plant defense against pathogen attack. The characterization of eds mutants will lead to identification of novel genes that play major roles in plant disease resistance. The EDS genes will be mapped and characterized in relation to their effect on defense gene expression and establishment of systemic acquired resistance. The range of pathogens that are affected by the eds mutations will be determined and EDS4 will be cloned using a map-based approach. Non-technical section The responses by which plants defend themselves from pathogen attack have not been subjected to rigorous genetic analysis, in part because the plant hosts have been used in molecular and biochemical analysis of disease resistance are difficult subjects for genetic studies due to large or polyploid genomes and long generation times. The use of the model plant, Arabidopsis thaliana, has made genetic studies feasible. Therefore, a powerful approach is now available for identifying regulatory factors and other defense response components in plants that are not already correlated with a known biochemical or molecular genetic response ***
