Study On The Structure And Phylogenetic Evolution Of Several Functional Genes In Yak

The functional genes on yak were cloned by T-A method,and was sequenced andanalyzed,and blastned with the other species in the GenBank at the nucleoside acid andamino acid levels,and the phylogenetic evolution trees about the yak and the otherspecies are constructed.The following results are achieved:(1)The lenghth of the GH gene in yak was 2847bp which including 5 exons and 4introns.The cDNA of GH was a 654bp nucleotide encoding a putative protein of 217amino acid (AA) residules,with a signal peptide of 26 AAs and the mature peptide of191 AAs.The comparison of these fragment sequences with those of other animalsthrough blastn of GeneBank,the results indicated that the homologies of nucleotidesequence of the GH gene of yak with Bos taurus are 98%,and with Bubalus bubalis,Capra hircus,Ovis aries are 97%,94%,93%,respectively.Molecular phylogenetic treeon these ruminant constructed by UPGMA,NJ and MP method,which showed that themolecular tree with relationship among species is unanimously.(2)The analysis and the comparison of arrays indicate that the numbers of exons andintrons of H-FABP gene are the same between the yak and cattle,sheep,goat,pig,human,chick,rat,mouse,they all have 4 exons and 3 introns.The data suggest that thegene from the yak was highly conserved with other species at the nucleic acid and AAlevel.The homology rate ofnucleoside acid arrays of the coding region ofH-FABP geneamong species of cattle,sheep,goat,pig,human,chick,rat,mouse and zebrafish are99.8%,97.8%,97.0%,92.8%,88.8%,83.3%,83.1%,76.4%,68.7% respectively;whilethe homology rate of AA arrays are 100%,96.9%,96.9%,92.4%,88.7%,85.7%,85.7%,77.4%,69.9% respectively.The molecular phylogenetic tree between breeds isconstructed from the nucleotide arrays of the H-FABP gene.The result indicates that theresult of phylogenetic clustering is consistent with the zoological classification,but alsosame to the conarrays of phylogenetic clustering between yak and other speciesconstructed by Fan Baoliang and Ou Jiangtao,indicating that H-FABP gene is also fit toconstruct molecular phylogenetic tree between different species.(3)The rate of the repetitive arrays is 13.07% in the nucleoside acid arrays ofH-FABP gene of the yak.Five repetitive elements are found in the intronâ… ,including aSINE/Artiodactyls element,a SINE/MIR3 element,a SINE/Bov-tA1 element and twoSINE/MIR elements.No repetitive element is found in intronâ…¡.Three repetitiveelements are found in intron3,including a SINE/MIR element,a LINE/L2 element anda SINE/Artiodactyls element.The rate is 11.85% for SINEs,6.44% for MIRs and 1.22% for LINEs respectively.In addition,LINE1,BovB/Art2,L3/CR1 repetitive elements,LTR anti-transcription element and DNA transposon element are not found in the arraysof this gene.(4)Homology rate of nucleoside acid arrays of part exonâ… of HSL gene between yakand cattle,zebu,buffalo,human (Homo sapiens),pig (Sus scrofa),rat (Rattus) andmouse (Mus musculus) is higher,which is 99.8%,99.6%,97.4%,90.6%,88.4%,83.5%,82.3% respectively.Homology of the corresponding AA arrays is also higher,that is100%,100%,98.2%,94.0%,92.2%,89.8%,89.8% respectively.Base variation betweenthe yak and the other species is mainly base transition and transversion,no baseinsertion and deletion and invertion is discovered in the nucleoside arrays comparison.Most of the single-base-variations occurs at the same nucleoside acid array site which isaccordance with the neutralism hypothesis on the molecular evaluation.(5)Molecular phylogenetic tree is constructed through multi-arrays comparison onpart nucleoside acid arrays of exonâ… of HSL gene.The result shows that firstly,zebu ismost closely related to cattle;secondly,closely related to yak,buffalo,pig,human,lastly,related to rat and mouse.The results of the phylogenetic trees reflect the molecularevolution relationship among these species,consistent with the zoological classification.The genetic distances among yak,cattle and zebu were relatively small,but geneticdistances between these three species and buffalo were relatively large.Therefore,itwas more reasonable to consider yak,cattle and zebu as independent species of thegenus Bos,while buffalo belongs to another category (Bubalus).(6)The results indicate that the yak HSP72 gene was an intron-free 1926bpnucleotide,encoding a protein of 641 AAs.The difference of HSP72 gene and HSP72protein does exist in yak and cow,swine,human,which is main cause of differentadaption of these species to temperature,the clustering analysis results of HSP72 geneand HSP72 protein in yak,cow,swine and human on different levels are consistent withthose of evolutional theory and other genes.(7) The EPO genes of Bazhou yak,Datong yak,Jiulong yak and Sanjiang cattle arecomprised by 5 exons and 4 introns,but the variance of the base coposition and size isdistinct.The lenghth of this gene was,respectively,3284bp,3281bp,3260bp and3245bp in Jiulong yak,Datong yak,Bazhou yak and Sanjiang cattle.The nucleotidesequences of EPO genes were compared,as a result,the homology was,respectively,99.7%,99.6%,99.5% between Datong yak and Bazhou yak,Jiulong yak,Sanjiangcattle,was 99.5%,99.4% between Bazhou yak and Jiulong yak,Sanjiang cattlerespectively,and was 99.4% between Jiulong yak and Sanjiang cattle,which indicatedthat there is high conservation among yaks,and the same between yaks and Sanjiangcattle.The difference at the nucleotide level of EPO gene may be related with high-altitude and oxygen-poor ecological environment,which is deserved to expore.(8)The comparation of the EPO AA sequence among Bazhou yak,Datong yak,Jiulong yak and Sanjiang cattle showed that Datong yak has the homology with Bazhouyak,Jiulong yak and Sanjiang cattle,was 100%,99.5%,99.5% respectively;andBazhou yak with Jiulong yak and Sanjiang cattle are all 99.5%;Jiulong yak withSanjiang cattle is 100%.That is to say,it is more conservative among yaks,and equallybetween yaks and Sanjiang cattle.However,there is some difference in AA level.So,itis further required to research whether the change effect the adaptive capability to theharsh natural condition.Molecular phylogenetic tree is constructed about Bazhou yak,Datong yak,Jiulong yak,Sanjiang cattle,bovine,pig and human on nucleoside acidarrays of EPO gene.The result indicates that the molecular phylogenetic tree reflectsthe evolution and genetic relationship in every researched species.