A Study On The Genome Repeats Of The Qinling Locust

[Objective]Genome Size,also known as C value,refers to the DNA content of the haploid genome of an organism,which is a unique attribute of organisms.The morphology,physiology and behavior of organisms are closely related to the genome size,and the most important reason for variationofthe genome size is the difference in the content of repetitive sequences.Therefore,the difference of repetitive sequences has received extensive attention from biologists.Whole genome sequencing shows that there is a positive correlation between genome size and repetitive sequences.Differences in repetitive sequences can also cause differences in genome length among eukaryotes.The relative frequency of insertion and deletion of repetitive sequence fragments is the main reason for the evolution of genome size.The relationship between the continuous enlargement of the genome sizeof Acridiodea insects with thetypes,contents and distribution pattern of repetitive sequences is still unclear.This article takes Sinopodisma qinlingensis as the research object,and genetic techniques such as genome skimming sequencing,flow cytometry,and fluorescence in situ hybridization were used to explore the type,content and chromosome position of the S.qinlingensis repetitive sequence.[Methods]In this study,flow cytometry was used to determine the genome size of female and male S.qinlingensis genomes using genome sizeof male Locusta migratoria manilensis(Mey)as an internal reference standard,and the difference in genome size between male and female was analyzed by t-test.Then,the next generation sequencing technology was used to determine S.qinlingensis genome and RepeatExplorer2 was used to analyze the extracted three 0.1X S.qinlingensis genome samples to determine the type and content of S.qinlingensis repetitive sequence,and average the content of the repeated sequences in the three results,the value is the result of the content of the final repetitive sequence,and the differences in the type and content of the repetitive sequence of S.qinlingensis obtained from different sample analysis are compared.After that,the maximum likelihood method was used in the MEGA software to construct the phylogenetic tree of the long terminal repeated(LTR)and the long interspersed nuclear elements(LINE)of S.qinlingensis repeat sequence,and analyze the evolutionary characteristics of LTR sequence and the LINE sequence.Finally,fluorescence in situ hybridization was used to determine the positions of 7 satellite DNAs and 5 LTRs in S.qinlingensis repeat sequence on the chromosome.[Results](1)The measured genome size of female S.qinlingensis is 11.3677 pg,and the genome size of male S.qinlingensis is 10.9455 pg,the difference between the two is 0.4222pg.Using the t-test method to compare and analyze the genome size between male and female individuals of S.qinlingensis,the results showed that there was a very significant difference between the two(P<0.01).(2)Using RepeatExplorer2 analysis,the total content of S.qinlingensis repeats is 63.58%,and the types and content of repeats are 45S_rDNA 0.38%,satellite 2.97%,LTR 17.74%,Penelope 2.22%,LINE 9.70%,maverick 0.33%,helitron 11.44%,plastid 0.01%,mitochondria 0.10%,unclassified mobile_element 5.10%,unclassified repeat 13.59%.Choosing different data samples has less impact on the total content of repetitive sequences and types of repetitive sequences,but has a certain impact on the content of a few repetitive sequence types,such as maverick.(3)The analysis of LTR phylogeny showed that the content of Ty3-Gypsy in LTR is the most.Analysis of LINE phylogeny showed that most of the LINE sequences have homology and the degree of evolutionary divergence is similar.(4)The results of fluorescence in situ hybridization showed that,except for the distribution pattern of SatDNA-07 on the chromosome which was non-clustered,the distribution patterns of the other 6 types of satellite DNA and 5 types of LTR on the chromosome were clustered.Most of the 7 satellite DNAs and 5 LTRs located on the autosomes,and only SatDNA-03 is located on the sex chromosome.In this study,the fluorescence signals of the 7 satellite DNAs were mostly distributed in the middle or both ends of the chromosomes.[Conclusions]The genome of S.qinlingensis is more than 10Gb,and the genomes size of male and female were significantly different(P<0.01);The total content of repetitive sequences is 63.58%,the random sampling has little effect on the study of repeated sequences;The Ty3-Gypsy has the highest content within LTR.