Maternal phylogeny of a newly-found yak population in china.

The Jinchuan yak is a new yak population identified in Sichuan, China. This population has a special anatomical characteristic: an additional pair of ribs compared with other yak breeds. The genetic structure of this population is unknown. In the present study, we investigated the maternal phylogeny of this special yak population using the mitochondrial DNA variation. A total of 23 Jinchuan yaks were sequenced for a 823-bp fragment of D-loop control region and three individuals were sequenced for the whole mtDNA genome with a length of 16,371-bp. To compare with the data from other yaks, we extracted sequence data from Genebank, including D-loop of 398 yaks (from 12 breeds) and 55 wild yaks, and whole mitochondrial genomes of 53 yaks (from 12 breeds) and 21 wild yaks. A total of 127 haplotypes were defined, based on the D-loop data. Thirteen haplotypes were defined from 23 mtDNA D-loop sequences of Jinchuan yaks, six of which were shared only by Jinchuan, and one was shared by Jinchuan and wild yaks. The Jinquan yaks were found to carry clades A and B from lineage I and clade C of lineage II, respectively. It was also suggested that the Jinchuan population has no distinct different phylogenetic relationship in maternal inheritance with other breeds of yak. The highly haplotype diversity of the Pali breed, Jinchuan population, Maiwa breed and Jiulong breed suggested that the yak was first domesticated from wild yaks in the middle Himalayan region and the northern Hengduan Mountains. The special anatomic characteristic that we found in the Jinchuan population needs further studies based on nuclear data.

Mipam TD ，Wen Y ，Fu C ，Li S ，Zhao H ，Ai Y ，Li L ，Zhang L ，Zou D ... -  《INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES》

Comprehensive investigation of nucleotide diverdity in yaks.

To understand the maternal genetic diversity of Tianzhu white yak better, we analyzed mtDNA D-loop sequences of 209 Tianzhu white yaks, which are from the central region of Tianzhu white yak habitat. Accordingly, a total of 45 haplotypes were identified in Tianzhu white yaks in this study, and 18 of them were unique. The nucleotide diversity and haplotype diversity of population studied were 0.024 ± 0.003 and 0.946 ± 0.007 respectively, revealing that Tianzhu white yak possess a relatively high genetic diversity. The phylogenetic analysis, combining D-loop sequences in this study with 533 previous published D-loop sequences of 13 yak breeds, indicated that Tianzhu white yaks fell mainly into haplogroup A and that a small portion belonged to haplogroups B, C, D and E. Moreover, six haplotypes of 20 individuals identified in Tianzhu white yak were in the taurine haplogroup, indicating hybridization between Bos taurus and Tianzhu white yaks. In summary, this study supplies a comprehensive maternal genetic pattern for Tianzhu white yak and provides a basic reference for future breeding programs to conserve the purebred Tianzhu white yak.

Yue X ，Liang Y ，Liang Y ，Li F ... -  《-》

Genetic Diversity, Molecular Phylogeny, and Selection Evidence of Jinchuan Yak Revealed by Whole-Genome Resequencing.

Jinchuan yak, a newly discovered yak breed, not only possesses a large proportion of multi-ribs but also exhibits many good characteristics, such as high meat production, milk yield, and reproductive performance. However, there is limited information about its overall genetic structure, relationship with yaks in other areas, and possible origins and evolutionary processes. In this study, 7,693,689 high-quality single-nucleotide polymorphisms were identified by resequencing the genome of Jinchuan yak. Principal component and population genetic structure analyses showed that Jinchuan yak could be distinguished as an independent population among the domestic yak population. Linkage disequilibrium analysis showed that the decay rate of Jinchuan yak was the lowest of the domestic yak breeds, indicating that the degree of domestication and selection intensity of Jinchuan yak were higher than those of other yak breeds. Combined with archaeological data, we speculated that the origin of domestication of Jinchuan yak was ∼6000 yr ago (4000-10,000 yr ago). The quantitative dynamics of population growth history in Jinchuan yak was similar to that of other breeds of domestic and wild yaks, but was closer to that of the wild yak. No significant gene exchange between Jinchuan and other domestic yaks occurred. Compared with other domestic yaks, Jinchuan yak possessed 339 significantly and positively selected genes, several of which relate to physiological rhythm, histones, and the breed's excellent production characteristics. Our results provide a basis for the discovery of the evolution, molecular origin, and unique traits of Jinchuan yak.

Lan D ，Xiong X ，Mipam TD ，Fu C ，Li Q ，Ai Y ，Hou D ，Chai Z ，Zhong J ，Li J ... -  《G3-Genes Genomes Genetics》

[Study on mitochondrial DNA genetic polymorphism of some yak breeds in China].

This study determined yak's complete sequence of mitochondrial DNA control region (D-loop) of 35 individuals in 5 yak breeds at the first time. The result showed that the length of D-loop in yak was 891 -895 bp. Content of nucleotide T, C, A, G were 28.5%, 25.3%, 32.5% and 13.7% respectively. There were 55 polymorphic sites (6.16% in total analyzed sites). The transition,transversion and insertion/deletion were found in this region.24 haplotypes was defined in this study, in which haplotype H4 and H6 were major haplotypes of Chinese yak. The distribution of all the haplotypes among the breeds was disequilibrium. The average diversity of haplotypes were 0.9697 +/-0.0180, indicating the abundance of haplotypes of yak's D-loop. The average nucleotide difference and the nucleotide diversity in Chinese yak breeds were 10.936% and 1.231% respectively. Nucleotide divergence and Kimura 2-parameter distance between yak breeds were 0.760% -2.155%, and 0.000-0.029 respectively. The results indicated that the genetic diversity of Chinese yak was very abundant. Analysis of molecular variance and network construction results indicated that there was significant divergence among Chinese yak breeds. The network construction indicated that Chinese yak had been divided into 2 types and had probably 2 maternal origins or 2 domesticated places.

Lai SJ ，Wang L ，Liu YP ，Li XW ... -  《-》

Mitogenomic diversity and phylogeny analysis of yak (Bos grunniens).

Mitochondrial genome has aseries of characteristics such as simple structure, no recombination, maternalinheritance, stable structure, fast evolution rate, and high copy number. Moreover, it is easy to be sequenced,contains high-resolution phylogenetic information, and exists in a wide rangeof taxa. Therefore, it is widely used in the study of biological phylogeny. Atpresent, phylogenetic studies focus mainly on D-loop region, cytochrome b gene,and protein-coding sequence. Phylogenetic studies using the mitochondrialcomplete sequence are rarely reported in yak. Therefore, the present studyaimed to construct phylogenetic tree using yak mitochondrial complete sequenceand compare the subsequent results with previous findings obtained usingpartial sequences. Complete mitochondrial sequences of five yakpopulations from Qinghai and Xinjiang were obtained. The mitotype diversity ofthe five populations was Xueduo yak (0.992 ± 0.015), Pamir yak (0.990 ± 0.014),Yushu yak (0.963 ± 0.033), Qilian yak (0.948 ± 0.036), and Huanhu yak (0.905 ±0.048), which showed a higher mitotype diversity compared with other breeds fromthe previous reports, including Jiulong yak, Maiwa yak, Zhongdian yak, andTianzhu yak. A total of 78 mitotypes were obtained from 111 individuals. Amongthese, Yushu yak, Huanhu yak, Xueduo yak, and Qilian yak all shared mitotypes,but the Pamir yak did not share mitotypes with these four populations.Phylogenetic analysis showed that yak populations were separable into threedistinct branches. The analysis identified a new phylogenetic branch containingboth wild and domestic yaks. The 155 mitotypes found in 206 individuals weredivided into 3 haplogroups by mitotype clustering. Thehaplogroup was not associated with the geographical distribution of yaks. Theyaks in the same population or the same ecological environment were distributedin different haplogroups. Among the threehaplogroups, haplogroup A and haplogroup B showed a star-shaped distribution ofmitotypes. The central mitotypes were widely distributed and had a highfrequency. Thegenetic diversity of yaks in Qinghai was high. Both domestic and wild yaks clusteredinto three branches.

Wang X ，Pei J ，Bao P ，Cao M ，Guo S ，Song R ，Song W ，Liang C ，Yan P ，Guo X ... -  《BMC GENOMICS》