title: Rapid reorganization of resistance gene homologues in cereal genomes.
abstract: We used conserved domains in the major class (nucleotide binding site plus leucine-rich repeat) of dicot resistance (R) genes to isolate related gene fragments via PCR from the monocot species rice and barley. Peptide sequence comparison of dicot R genes and monocot R-like genes revealed shared motifs but provided no evidence for a monocot-specific signature. Mapping of these genes in rice and barley showed linkage to genetically characterized R genes and revealed the existence of mixed clusters, each harboring at least two highly dissimilar R-like genes. Diversity was detected intraspecifically with wide variation in copy number between varieties of a particular species. Interspecific analyses of R-like genes frequently revealed nonsyntenic map locations between the cereal species rice, barley, and foxtail millet although tight collinear gene order is a hallmark of monocot genomes. Our data suggest a dramatic rearrangement of R gene loci between related species and implies a different mechanism for nucleotide binding site plus leucine-rich repeat gene evolution compared with the rest of the monocot genome.
authors.affiliation: The Sainsbury Laboratory, Colney Lane, NR4 7UH Norwich, United Kingdom.
authors.forename: D
authors.initials: D
authors.lastname: Leister
authors.forename: J
authors.initials: J
authors.lastname: Kurth
authors.forename: D A
authors.initials: DA
authors.lastname: Laurie
authors.forename: M
authors.initials: M
authors.lastname: Yano
authors.forename: T
authors.initials: T
authors.lastname: Sasaki
authors.forename: K
authors.initials: K
authors.lastname: Devos
authors.forename: A
authors.initials: A
authors.lastname: Graner
authors.forename: P
authors.initials: P
authors.lastname: Schulze-Lefert
mesh_terms: D002874:Chromosome Mapping; D002523:Edible Grain / Q000235:genetics*; D019143:Evolution, Molecular; D014644:Genetic Variation; D018745:Genome, Plant; D001467:Hordeum / Q000235:genetics; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics; D008897:Panicum / Q000235:genetics; D010935:Plant Diseases / Q000235:genetics