Link to home

Cell Death Mediated by the N-Terminal Domains of a Unique and Highly Conserved Class of NB-LRR Protein

August 2011 , Volume 24 , Number  8
Pages  918 - 931

Sarah M. Collier,1,2 Louis-Philippe Hamel,3 and Peter Moffett1,3

1Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, NY 14853 U.S.A.; 2Department of Plant Breeding & Genetics, Cornell University, Ithaca, NY 14853 U.S.A.; 3Centre de Recherche en Amélioration Végétale, Département de Biologie, Université de Sherbrooke, Sherbrooke, QC, J1K 2R1 Canada

Go to article:
Accepted 11 April 2011.

Plant genomes encode large numbers of nucleotide-binding, leucine-rich repeat (NB-LRR) proteins, many of which are active in pathogen detection and defense response induction. NB-LRR proteins fall into two broad classes: those with a Toll and interleukin-1 receptor (TIR) domain at their N-terminus and those with a coiled-coil (CC) domain at the N-terminus. Within CC-NB-LRR-encoding genes, one basal clade is distinguished by having CC domains resembling the Arabidopsis thaliana RPW8 protein, which we refer to as CCR domains. Here, we show that CCR-NB-LRR-encoding genes are present in the genomes of all higher plants surveyed, and that they comprise two distinct subgroups: one typified by the Nicotiana benthamiana N-required gene 1 (NRG1) protein and the other typified by the Arabidopsis activated disease resistance gene 1 (ADR1) protein. We further report that, in contrast to CC-NB-LRR proteins, the CCR domains of both NRG1- and ADR1-like proteins are sufficient for the induction of defense responses, and that this activity appears to be SGT1-independent. Additionally, we report the apparent absence of both NRG1 homologs and TIR-NB-LRR-encoding genes from the dicot Aquilegia coerulea and the dicotyledonous order Lamiales as well as from monocotyledonous species. This strong correlation in occurrence is suggestive of a functional relationship between these two classes of NB-LRR proteins.

© 2011 The American Phytopathological Society