Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/30/2006
Publication Date: 3/14/2006
Citation: See, D.R., Brooks, S.A., Nelson, J.C., Brown Guedira, G.L., Friebe, B., Bikram,G. 2006. Gene evolution at the ends of wheat chromosomes. Proceedings of the National Academy of Science USA. 103:4162-4167. Interpretive Summary: The major cereal crop species wheat, maize, barley, rye, sorghum and rice diverged over 65 million years ago. However, because of their common evolutionary origin, they still show a high degree of gene similarity and conservation of gene order along chromosomes. The information from the recently completed rice genome sequence is used as a basis to compare gene evolution in the grasses. The DNA sequences of mapped expressed genes from wheat chromosome 4B were aligned with sequences from rice chromosome 3. These wheat—rice comparative genomics results support the proposition that chromosome expansion and gene evolution occur preferentially at the ends of chromosomes, driven by duplication and divergence associated with high rates of recombination.
Technical Abstract: Wheat ESTs mapped to deletion bins in the distal 42% of the long arm of chromosome 4B were presumptively ordered in silico based upon BLASTn hits against rice BACs. The ESTs spanned 29 cM on the short arm of rice chromosome 3, known to be syntenic to wheat group-4 chromosomes. Fine-scale deletion-bin and genetic mapping confirmed a high degree of synteny throughout the distal region. One inversion was identified spanning a 5 cM region involving two deletion bins. Wheat ESTs showing no sequence homology in rice mapped to the terminal 5% of the chromosome, a region in which 27% of ESTs were duplicated and which accounted for 70% of the recombination in the 4BL arm. At the genome level, ESTs showing no sequence homology to the rice genome mapped to the terminal bins or rarely to interstitial chromosome regions known to be hot spots for recombination. These wheat—rice comparative genomics results support the proposition that chromosome expansion and gene evolution occur preferentially at the ends of chromosomes, driven by duplication and divergence associated with high rates of recombination.