Cloning And Localization Of A Repetitive DNA Sequence Of Dong Xiang Wild Rice Oryza Rufipogon Griff

The nuclear genome contains approximately 50% repetitive DNA sequence in rice. Amplification and introgression of repetitive DNA sequences in the genome of higher eukaryotes are unknown clearly. Cloning and localization of specific repetitive DNA sequences, then making an analysis to these sequences will be helpful to study the structure of the chromosomes and function of repetitive sequences in plants.Bacterial artificial chromosome libraries was constructed which including DNA fragments of Dong xiang wild rice (Oryza rufipogon Griff) with enzyme partial digestion, 7 positive BAC clones were selected by colony hybridization and dot-blot hybridization, which include specific repetitive DNA sequences of Dong xiang wild rice probably.One BAC clone named BAC40 was selected to construct a subclone library for future analysis. Twenty clones were picked to sequence after dot-blot hybridization with two different probes, which showed strong signals with Oryza rufipogon Griff (Dong xiang wild rice) DNA probe but faint or no signals with Oryza officinalis (CC genome) DNA probe. Analysis to sequence revealed that BAC40 include several kinds of repetitive DNA sequences, and 7 different kinds of repetitive DNA sequences (B1, H1, C1, D3, D8, E4, H2) were studyed here. The BAC subclones were aligned withrelative sequence in rice (Indica) genome, and the result indicated that BAC40 is localled at the site near the 5th chromosome centromere,in addtion, these repetitive DNA sequences can be found in other chromosome. The sequence is up to 90% homology to sequence of rice (Indica) genome sequence. But the copy number of them is different in the different chromosome. The result of fluorescence in situ hybridization with BAC40 probe indicated that signals could be found at almost the same site near the centromere on several different chromosomes, and also in the middle of chromosome arms. The same or similar repetitive DNA sequence is not reported so far in wide rice. In order to predict the fuction of these sequence, Bioinformation method was used and found that Bl and HI sequences were part of transposon protein sequence also, the other five sequences (Cl, D3, D8, E4, H2) were related to transposon sequence also. So these results meant that these repetitive sequences would be dispersed on the chromosomes and with a relationship to transposon sequences. In addition, these sequences changed quickly in copy number and nuclear compositon, even if in the same genome, so they are as useful molecular markers for studying plant genome evolution and species diversity.