Mining And Analysis Of Centromere Specific Sequences In Gossypium Thurberi

Centromere as an important component of the chromosome in mitosis and meiosis plays an important role in the process of centromeric chromatin is mainly composed of repetitive sequences,including highly repetitive centromere-specific retrotransponson and satellite repeats,highly changes due to the centromere repeat sequences,the centromere repetitive sequence evolution mechanism has not yet have enough evidence to prove.Cotton is an important natural fibre and cash crops,has the important status in agriculture as the cotton genome sequencing,study of centromere on cotton has been in progress in order to further understand the evolution of the centromere repeating columns,this study diploid group D cotton Gossypium thurberi?G.thurberi,D₁?as material,through chromatin immunoprecipitation?ChIP?and fluorescence in situ hybridization?FISH?to detect the centromere series is analyzed,the main research results are as follows:1.ChIP-DNA sequences were obtained by chromatin immunoprecipitation with CENH3 antibody,and the positions of the sequences on chromosomes were verified by FISH.ChIP-DNA library was constructed and genome sequencing was performed.A total of 19 centromere repeats were obtained by bioinformatics analysis.2.19 repeat sequences were verified by FISH,10 of which generated signals in the centromere region of G.hirsutum,and there was no hybridization signal in the G.arboretum centromere region of diploid group A.Therefore,it can be speculated that these 10 repeats originated from the D genome and were preserved in the tetraploid evolution.Two of the duplicates?CL179 and CL234?had hybridization signals in the centromere region of the A and D subgenomes of G.hirsutum,and the number of copies of the sequences increased.It can be speculated that during the formation of allotetraploid,the duplicates were amplified and invaded into the A subgenome;three repeats?CL149 CL95 and CL283?were found in the centromere region of G.thurberi and G.hirsutum,but not in the centromere region of G.raimondii and G.arboretum in diploid D group and A group by comparison with centromere repeat sequences of G.raimondii and FISH detection,therefore,it can be considered that this is a specific sequences of centromere of G.thurberi and has been preserved during the evolution of tetraploid.By Comparing with the repeat sequences of G.raimondii centromere,it is inferred that the repeat sequences of G.thurberi centromere is derived from retrotransponson.Interestingly,FISH verified that the centromere repeats CL185 and CL186 were stronger on the chromosomes of G.thurberi and G.mustelinum than in G.hirsutum,it is speculated that these two repeated sequences have transposon events or genome replication,which will preferentially select to evolve and amplify in the chromosomal region of G.mustelinum.3.The repeat sequences in the tetraploid upland cotton centromere region were compared with the G.hirsutum genome sequences in the cotton database.Three of the repeats?CL23 CL179 and CL277?were sparsely distributed on the G.hirsutum chromosomes centromeric sparse or even no,and it was speculated that the repeat sequences might not be easily assembled in the process of genome sequence assembly.This study based on the sequence G.thurberi centromere appraisal to the initial analysis of the evolution model,to further study the structure and function of cotton centromere support,to promote cotton genome research,is helpful to reveal the centromere repetitive sequence evolution mechanism,as well as G.thurberi as tetraploid D subgroups of donor to provide certain theoretical support.