Analysis Of Population Genetic Structure And Cloning,expression Profile Of Hair Color Related Gene STX17 In Maiwa Yak Conservation Population

Maiwa yak,with meat and milk production,is an excellent local yak resource in Qinghai Tibet Plateau.In this study,we sequenced three Maiwa yak conservation populations(including QH,FZ and FL)from Longri breeding farm of Sichuan province by GBS simplified genome sequencing technology.Based on the detected SNPs information,the genetic diversity and the genetic relationship of three Maiwa yak conservation populations were investigated,and the selection pressure analysis between them and the association analysis of coat color candidate genes were conducted.The detailed research contents and main results are as follows:1.A large number of genomic genetic variations data,including 1,628,805 SNP loci,which are obtained from Maiwa yak population sequence,and covering a wide range of genomes.It is no significant difference between three conservation populations of the observed heterozygosity(Ho),and the average Ho of the total population were close to the average expected heterozygosity(He).Combined with linkage disequilibrium(LD)analysis,the results showed that three conservation populations were moderately heterozygous populations,which were in genetic balance and less affected by foreign factors,and the degree of genetic variation of the three populations was the same.The genetic distance(DR)and genetic differentiation index(FST)of FZ and QH populations were the largest.Combined with principal component analysis(PCA),phylogenetic tree and population structure analysis,it shows that the pure individuals with blood relationship in the three populations can be grouped separately,FZ and QH population have differentiation,and only a small number of individuals have blood relationship crossing and segregation.In recent years,the three populations in Longri breeding farm not only fixed the original typical appearance,but also gradually purified the blood relationship in the population,which shows that the seed conservation and breeding method of open population subculture breeding is reasonable,but the quality and pedigree information of excellent bulls still need to be strictly controlled in the process of population subculture breeding.2.FST and Pi methods were used to analyze the selected signals of three Maiwa yak conservation populations.There were 646 and 632 genomic regions and 105 and111 significantly different genes in the selected regions of FL,FZ and QH population respectively(top 5% was the threshold standard).These genes were involved in the regulation of immune defense,neurobehavior and transportation function.Through GO enrichment and KEGG pathway analysis,it was found that these genes were mainly enriched in cells responding to the stimulation of DNA damage Ubiquitin protein ligase activity,Endoplasmic reticulum tissue and Chloride channel complex,as well as GABAergic synapses,Fatty acid biosynthesis,Oxytocin signaling pathway,Vascular smooth muscle contraction,Hypothalamic gonadotropin-releasing hormone secretion and other pathways;these genes Including the muscle development-related genes MEF2 and MSRA of the QH population,the reproductive physiology-related genes PIWIL4 and ESR1 of the FZ population,and the CPQ and PPP3 CC of the QH population,and the immune diseases related genes of the three populations ZNF385 B,TRIM14 and SETD8,etc.,and the coat color-related genes STX17,NR4A3 of the three populations,GNAQ of the FZ population,and KIT of the QH population.It provides a new clue for further exploring the mechanism of population evolution of Maiwa yak.3.The selection signal region of the three conservation groups is locked to the coat color-related gene syntaxin STX17,and its ORF sequence was successfully cloned with a length of 909 bp,encoding 302 amino acids.The analysis found that the two transmembrane domains of the gene formed a hairpin structure,located on autophagosomes;STX17 is widely expressed in six tissues including heart,spleen and skin,and its expression level is higher in gray skin than in black skin.In this study,GBS technology was used to reveal the genetic diversity and genetic structure of the three preserved populations of Maiwa yak.The FZ population and the QH population showed a trend of genetic differentiation,and the effect of grouping was reflected;105 and 111 differences were found in the analysis of the selection signal between the populations.Gene,the conservation population has undergone artificial selection on coat color,immunity and reproductive traits;and it is proved by fluorescence quantitative PCR that the STX17 gene is related to the formation of coat color of Maiwa yak,which provides an important reference for the conservation and breeding of Maiwa yak.