QTL Fine Mapping Of Telomere Length In Oryza Sativa L.

Telomere is an important structure of eukaryotic chromosome,which is composed of DNA and related proteins.It contains a series of repetitive sequences,and there are differences in different species.Telomere consists of both single stranded and double stranded DNA.The single stranded DNA domain normally has G-overhang terminus.Because of the specificity of the DNA structure,D-loop?T-loop and G-quadruplex can be formed at the end of telomere,which play an important role in the protection of chromosome ends.The core telomere binding protein is composed of 6 subunits and called shelterin complex in human cells,and CTS complex in yeast.The differences of telomere binding proteins in different species indicate that there is a large variation in telomere structure in the process of evolution.As cells divide,telomeres are shortened inevitably because of the DNA end replication defect.Telomerase could consistently extend at the 3'-end by reverse transcription with its template RNA and overcome the problem.Telomere protects the chromosome as a ?cap?,maintaining the stability and integrity of chromosome,avoiding the end-to-end fusion,and is very important for cell cycle.Recently,studies showed that the changes of telomere length are related to cell growth,cellular senescence and death,and tumor.It is puzzled that individual telomeres have dramatically different length within the same telomerase activation and share within the same cell division and circumstance.Obviously,individual telomere length may not be determined by telomerase activity but also the other factors.It is little known about any genetic factors causing the distribution of telomere length,although the studies about human telomere and telomerase have been carried out closely.So it is very important to know more about it.Rice is a good model plant,and the genome has been a completed sequencing profile that comprehensive genomic information can be easily retrieved to compare with variation of telomere length.Besides,the telomeric length is obvious differences between japonica subspecies and indica subspecies of rice.Compared with animals,rice is more easier to construct genetic population,and it has shorter telomeres making much suitable for the PCR processing.In this study,Ribenqing(japonica)and Guangluaisihao(indica)were selected.In the last few years,with the development of molecular technology,QTL(Quantitative Trait Locus)is widely used in plant.In rice,5416 QTLs including rice growth period,plant height and its characters,leaf and root traits and so on,were successfully located.These provide an important basis for measuring rice telomere length and studying its genetic characters.QTL analysis of telomere length trait in rice has been carried out,and it indicated that there could be a major gene on chromosome 12 that regulates the telomere length remarkably,and the gene is between primer RM20 and RM19,genetic distance is 5.848 cM.It is necessary shortening the QTL positioning interval and finally positioning or cloning the related genes that controls the telomere length.Three series of molecular markers were designed after analyzing the sequence information about the target range of parents.Then construct the linkage map and map the QTL.Finally two intervals were confirmed between marker RBQ-14 and RBQ-11?marker RBQ-11 and RBQ-34.The relatively short sequence was selected for further analysis.We obtained 3246 bp nucleotide sequence of Ribenqing and Guangluaisihao,and then made a comparative analysis of the gene structure,the promoter region and the transcriptional regulatory elements which were predicted by different databases.The results showed that the quantities and position of exons were different,and both of parents had similar transcriptional regulatory elements.Search the amino acid sequence encoded by the gene in Blast,and the result indicated that it was similar with three protein families,FAM53,APC and CAF-1 of homo sapiens.In cells,CAF-1 is found as histones molecular chaperone during DNA replication and DNA repair.Besides,deletion of the corresponding CAC genes in Arabidopsis thaliana results in telomere shortening and loss of 45 S rDNA.Thus assumes that the QTL between marker RBQ-11 and RBQ-34 has regulatory role on rice telomere length.These results lay a solid foundation for studying the sequence between marker RBQ-14 and RBQ-11,verifying the role of the QTL loci,and also very important for the research on rice genetic mechanism of telomere length.