|Friebe, Bernd -|
|Zhang, Peng -|
|Gill, Bikram -|
Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 17, 2009
Publication Date: December 1, 2009
Citation: Qi, L., Friebe, B., Zhang, P., Gill, B.S. 2009. A Molecular-Cytogenetic Method for Locating Genes to Pericentromeric Regions Facilitates a Genomewide Comparison of Syntency Between the Centrometric Regions of Wheat and Rice. Genetics. 183:1235-1247. Interpretive Summary: The centromere is a component of a chromosome that is visible under a microscope. It plays an essential role in every eukaryotic cell, that is, accurate segregation of the chromosomes during cell division. The cereal crops wheat (1x=7) and rice (1x=12) share 65 million years of evolutionary history, differ in basic chromosome number and genome size (40-fold) and yet maintain large blocks of gene similarity and in some cases whole chromosome similarity. However, the information about centromere similarity between rice, wheat and other species is still limited because most of the rice centromere cores are in positions where DNA sequences are not available, and there is also a breakdown of similarity in the centromeric regions. It was recently discovered that rice centromeres often contain genes. Classically, wheat cytogenetic stocks have been used for centromere mapping of genes. We mapped rice centromere genes on wheat aneuploid stocks to study centromere similarity between rice and wheat. One of the most important findings of the present study is that most wheat centromeres showed one to one correspondence to rice centromeres. The depicted framework provides a working model for further studies on the structure and evolution of cereal chromosome centromeres.
Technical Abstract: Centromeres, because of their repeat structure and lack of sequence conservation, are difficult to assemble and compare across organisms. It was recently discovered that rice centromeres often contain genes. This suggested a method for studying centromere homologies between wheat and rice chromosomes by mapping rice centromeric genes onto wheat aneuploid stocks. Three of the seven cDNA clones of centromeric genes from rice centromere 8 (Cen8), 6729.t09, 6729.t10 and 6730.t11 which lie in the Cen8 kinetochore region, and three wheat ESTs, BJ301191, BJ305475, and BJ280500, with similarity to sequences of rice centromeric genes were mapped to the centromeric regions of the wheat group-7 (W7) chromosomes. A possible pericentric inversion in chromosome 7D was detected. Genome-wide comparison of wheat ESTs that mapped to centromeric regions against rice genome sequences revealed high conservation and a one-to-one correspondence of centromeric regions between wheat and rice chromosome pairs W1-R5, W2-R7, W3-R1, W5-R12, W6-R2, and W7-R8. The W4 centromere may share homology with R3 only or with R3+R11. Wheat ESTs that mapped to the pericentromeric region of the group-5 long arm anchored to the rice BACs located in the recently duplicated region at the distal ends of the short arms of rice chromosomes 11 and 12. A pericentric inversion specific to the rice lineage was detected. The depicted framework provides a working model for further studies on the structure and evolution of cereal chromosome centromeres.