Resistance rodeo: rounding up the full complement of Arabidopsis NBS-LRR genes.

Plant resistance ( R ) genes encode proteins that mediate the recognition of corresponding pathogen-encoded avirulence (Avr) proteins, triggering localized cell death (the hypersensitive response) and systemic acquired resistance. A large number of R genes have been characterized from numerous plant species that collectively confer resistance to a wide range of pathogens, including viral, bacterial, and fungal pathogens, and even to some nematodes and insects. Plant nucleotide binding site–Leu-rich repeat (NBS-LRR) proteins appear to function principally (perhaps exclusively) in signaling associated with the recognition of and resistance to pathogens and represent the largest of five known classes of R proteins (reviewed by Dangl and Jones, 2001). In this issue of The Plant Cell , Meyers et al. (pages 809– 834) present an analysis of the structure, arrangement, and phylogeny of the full complement of 149 NBS-LRR genes in the Arabidopsis ecotype Columbia genome (Figure 1). Despite the wealth of information on the structure and function of NBS-LRR genes that has come from numerous primary research and review articles in recent years, this comprehensive analysis offers novel insights into genome evolution in general and R gene evolution in particular and provides a useful World Wide Web–based resource for other researchers in the field. Meyers et al. started their analysis by manually reannotating all previously identified NBS-LRR genes and searching the genome sequence for genes missed in the earlier annotations. An important outcome of this work was a change in annotation of some 36% of previously identified NBSLRR genes, suggesting the weakness of current automated annotation methods. This work also identified 11 new pseudogenes, which tend to be annotated as fullFigure 1. Lassoing and Branding R Genes: Progressively More Fine-Scale Analysis of NBS-LRR– Encoding Genes.