The genetic architecture of resistance.
Plant resistance genes (R genes), especially the nucleotide binding site leucine-rich repeat (NBS-LRR) family of sequences, have been extensively studied in terms of structural organization, sequence evolution and genome distribution. These studies indicate that NBS-LRR sequences can be split into two related groups that have distinct amino-acid motif organizations, evolutionary histories and signal transduction pathways. One NBS-LRR group, characterized by the presence of a Toll/interleukin receptor domain at the amino-terminal end, seems to be absent from the Poaceae. Phylogenetic analysis suggests that a small number of NBS-LRR sequences existed among ancient Angiosperms and that these ancestral sequences diversified after the separation into distinct taxonomic families. There are probably hundreds, perhaps thousands, of NBS-LRR sequences and other types of R gene-like sequences within a typical plant genome. These sequences frequently reside in 'mega-clusters' consisting of smaller clusters with several members each, all localized within a few million base pairs of one another. The organization of R-gene clusters highlights a tension between diversifying and conservative selection that may be relevant to gene families that are unrelated to disease resistance.
Young
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Department of Plant Pathology, 495 Borlaug Hall, University of Minnesota, St. Paul 55108, USA. neviny@tc.umn.edu.
D020816:Amino Acid Motifs; D000818:Animals; D019143:Evolution, Molecular; D017343:Genes, Plant / Q000235:genetics* / Q000502:physiology; D018745:Genome, Plant; D005810:Multigene Family / Q000235:genetics; D010802:Phylogeny; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology* / Q000469:parasitology; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D010944:Plants / Q000235:genetics* / Q000382:microbiology / Q000469:parasitology; D013045:Species Specificity
D010940:Plant Proteins