ARABIDOPSIS - A WEED LEADING THE FIELD OF PLANT-PATHOGEN INTERACTIONS

Arabidopsis thaliana, like other flowering plants, exhibits specificit y in resistance to plant pathogens. Using the genetic diversity presen t in differential accessions of Arabidopsis, over 49 loci which govern pathogen specificity have been identified. Similar to resistance gene s from other plant species, the Arabidopis RPS2, RPM1, and RPP5 resist ance genes encode leucine-rich repeat proteins, suggesting that Arabid opsis behaves in a manner similar to other angiosperms in disease resi stance mechanisms. Novel insights into events subsequent to pathogen r ecognition in Arabidopsis have been obtained from analysis of mutants altered in defense. Not only have signal transduction pathways been de duced, but several genes involved in post-recognition events have been cloned using positional cloning methods. One such gene, NPR1, encodes an ankyrin-repeat protein with similarity to animal proteins which re gulate the inflammatory response in mammalian cells and antifungal res ponses in Drosophila, suggesting an ancestral link in defense response s between the animal and plant kingdoms. NPR1 is not alone in providin g novel insights into the mechanism(s) of disease resistance, the ein2 and hls1 mutants have clearly demonstrated that ethylene has a role i n plant defense, and the cloning of the LSD1 gene provides a molecular tool to examine reactive oxygen species in programmed cell death. (C) Elsevier, Paris.