Rapid reorganization of resistance gene homologues in cereal genomes.
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.
Leister
D
D
The Sainsbury Laboratory, Colney Lane, NR4 7UH Norwich, United Kingdom.
Kurth
J
J
Laurie
D A
DA
Yano
M
M
Sasaki
T
T
Devos
K
K
Graner
A
A
Schulze-Lefert
P
P
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