title: Convergent evolution of disease resistance gene specificity in two flowering plant families.
abstract: Plant disease resistance (R) genes that mediate recognition of the same pathogen determinant sometimes can be found in distantly related plant families. This observation implies that some R gene alleles may have been conserved throughout the diversification of land plants. To address this question, we have compared R genes from Glycine max (soybean), Rpg1-b, and Arabidopsis thaliana, RPM1, that mediate recognition of the same type III effector protein from Pseudomonas syringae, AvrB. RPM1 has been cloned previously, and here, we describe the isolation of Rpg1-b. Although RPM1 and Rpg1-b both belong to the coiled-coil nucleotide binding site (NBS) Leu-rich repeat (LRR) class of R genes, they share only limited sequence similarity outside the conserved domains characteristic of this class. Phylogenetic analyses of A. thaliana and legume NBS-LRR sequences demonstrate that Rpg1-b and RPM1 are not orthologous. We conclude that convergent evolution, rather than the conservation of an ancient specificity, is responsible for the generation of these AvrB-specific genes.
authors.affiliation: Department of Biology, Indiana University, Bloomington, Indiana 47405-7107, USA.
authors.forename: Tom
authors.initials: T
authors.lastname: Ashfield
authors.forename: Laura E
authors.initials: LE
authors.lastname: Ong
authors.forename: Kan
authors.initials: K
authors.lastname: Nobuta
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Schneider
authors.forename: Roger W
authors.initials: RW
authors.lastname: Innes
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D007113:Immunity, Innate / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D044224:Pseudomonas syringae / Q000235:genetics / Q000254:growth & development; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013025:Glycine max / Q000235:genetics* / Q000382:microbiology; D013045:Species Specificity
chemical_list: D029681:Arabidopsis Proteins; C100931:AvrB protein, Pseudomonas syringae; D001426:Bacterial Proteins; D010940:Plant Proteins; C095014:RPM1 protein, Arabidopsis; C420919:avrRpt2 protein, Pseudomonas syringae