Studies Of Centromere-Specific Sequences In Cotton

The centromere is an important component element in eukaryotic chromosomes. In mitosis and meiosis, centromeres are not only responsible for holding sister chromatids together but also providing a domain for kinetochore assembling and spindle fiber attaching. So it played an important role in the process to ensure normal segragation of chromosomes and accurate transmission of genetic material between generations. These functions are very conservative, but diverse in DNA sequence of different species.There are strikingly different centromeric DNAs in different organisms. Centromere is the most difficult area for the eukaryotic genome sequencing research. Because centromeres contain large amounts of repetitive sequences, it is very difficult to carry out precise sequencing.Cotton is the most important fiber economic crops in China and the world. Gossypium contain 4 cultivated species and 46 wild species belongs into the A, B, C, D, E, F, G, K and AD genomes. Its rich germplasm resources provide a large number of experimental materials in cotton genetic researches. There are very limited understanding of centromeric DNA sequences in cotton, large-scale sequencing and analysis of centromeric regions in Gossypium has no reports so far. In the present research, we obtained centromeric candidate BAC clones and retrotransposons by screening the BAC library following testing by FISH in G.arboreum. We also isolated three tandem repeats from G. raimondii and identified the SSR markers in our genetic maps. The main results are as follows:1. Isolation and analysis of centromeric retrotransposons in A-diploid cotton:Based on previous studies, we screened JLZM BAC library by PCR method.22 positive candidate clones of centromere-specific BAC were obtained. By FISH test, two BACs 81E7 and 145E14 were identified as centromere-specific clones. By sequence analyzing and FISH testing, three centromere-specific retrotransposons we verified.2. Isolation of centromeric-specific sequences in D-diploid cotton:Based on sequence comparison and FISH analysis, we identified three centromere-specific tandem repeats in G. raimondii.3. The integration of centromere positions to genetic map:By comparison the sequences of SSR with centromeric region, centromeric SSR. markers were verified. Therefore, the centromeres were mapped in 11 of linkage groups in current genetic map of cotton.