Functional Sequence Analysis Of Centromere From The Halophyte Halogeton Glomeratus And Its Comparison With Chenopodiaceae Plants

The plants belonging to quinoa are mostly distributed in arid saline land.These species have the remarkable ability to control sand,conserve soil,reduce water evaporation,and salt tolerance and drought.There are containa lot of favorable genes for salt and alkali resistant genes.Therefore,the study of these species is of great significance to the improvement of crop agronomic characters and the cultivation of salt tolerance crops.Halogeton glomeratus is an annual dicotyledonous plant and belongs to the Halogeton genus of Chenopodiaceae.It is a typical halophyte and has strong salt tolerance.Chenopodium quinoa Willd.is an annual dicotyledonous plant of the Chenopodiaceae genus and has strong drought resistance and salt tolerance.Beta vulgaris L.is a biennial herb of the Beta genus.It is also one of the drought resistant and barren crops.They are good wild resources for obtaining salt and drought tolerance genes,and they also have high utilization value in the cultivation of new varieties of drought resistant and salt tolerant crops..The centromere sequence is directly related to the correct separation of the sister chromosome and the identification of homologous chromosomes in mitosis and meiosis.The centromere sequence plays an important role in the evolution of species.The highly repetitive sequences in the genome are also related to the evolution and expansion of the genome.Analysis of the centromere and repeat sequences of related species would lay a foundation for further study of the species and its utilization.So far,the genome sequencing of Beta vulgaris L.and Chenopodium quinoa Willd.has been completed.In this study,in order to excavate the law of genome evolution of quinoa,the homologous cloned centromere retrotransposon Beetle and satellite DNA sequence pBv were used to explore the similarities and differences in the centromeric sequence between the three species of Halogeton glomeratus,Beta vulgaris L.,and Chenopodium quinoa Willd..And then,the FISH analysis was performed to study the composition of the retroviral transposon Beetle and the satellite DNA sequence pBv in the chromosome of Halogeton glomeratus.The results are as follows:1.Using the centromere retrotransposon sequence Beetle7 found in Beta vulgaris L.genome,the primers were designed based on conserved sequences such as LTR,Gag,and RT,and the homologous clones were carried out in the Halogeton glomeratus and Chenopodium quinoa Willd..Results showed that the target sequences of LTR,Gag,and RT were obtained from Halogeton glomeratus,indicating that Beetle retrotransposons exist in Halogeton glomeratus.The sequence of RT only was amplified in Chenopodium quinoa Willd..and the important constitutional sequences LTR and Gag of the centromeric retrotransposons were not amplified.Therefore,we concluded that there is no such retrotransposon in Chenopodium quinoa Willd..2.Using the reverse transposon Beetle-H sequence plasmid made from the homologous clone of the Halogeton glomeratus,the FISH analysis was carried out with the metaphase chromosome of the Halogeton glomeratus root tip cell.The probe signal was only distributed on the partial centromeres of the 18 chromosomes of Halogeton glomeratus.The centromere function sequence Beetle7,which was widely distributed on each chromosome in Beta vulgaris L..However,it is less abundant in the Halogeton glomeratus.In the next step,we will verify its relationship with the centromeric functional sequence of Halogeton glomeratus by immunoprecipitation(ChIP)method.It is speculated that there exist other unknown centromeric functional sequences in Halogeton glomeratus,which need further study.3.The hybridization signal of the centromere sequence of the Halogeton glomeratus was weak.Because of the chromosome size of the the Halogeton glomeratus was very small and the Beetle-H abundance of the centromere sequence was also small,we think these reasons lead to weak hybridization signals and indistinguishable.We intend to improve the method in future experiments to obtain better chromosome and strong hybridization signals.4.The homologous cloning of Beta vulgaris L.the genome centromere satellite DNA pBv(327bp)in Halogeton glomeratus and Chenopodium quinoa Willd.was carried out.Results showed that homologous sequence was not obtained in Chenopodium quinoa Willd..The Beetle element was present in both Halogeton glomeratus and Beta vulgaris L..However,it was not present in Chenopodium quinoa Willd..Therefore we could confirm the relationship between Halogeton glomeratus and Beta vulgaris L.is closer in the Chenopodiaceae than Chenopodium quinoa Willd..In situ hybridization analysis of metaphase chromosomes in Halogeton glomeratus showed that the satellite DNA pBv is distributed in the centromere,and dispersed on the some chromosome arms.Therefore,the Beta vulgaris L.centromere satellite DNA is no longer a centromere satellite DNA in Halogeton glomeratus,and exists on the chromosome arms.