title: Cell death mediated by the N-terminal domains of a unique and highly conserved class of NB-LRR protein.
abstract: 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.
authors.affiliation: Boyce Thompson Institute for Plant Research, Department of Plant Breeding & Genetics, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Collier
authors.forename: Louis-Philippe
authors.initials: LP
authors.lastname: Hamel
authors.forename: Peter
authors.initials: P
authors.lastname: Moffett
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016923:Cell Death / Q000502:physiology*; D003001:Cloning, Molecular; D017124:Conserved Sequence; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D018515:Plant Leaves
chemical_list: D029681:Arabidopsis Proteins