How Pigs Adapted To Altitude

A whole-genome sequencing study has undercovered the genes that helped pigs adapt to hot and cold environments at different altitudes.

AsianScientist (Feb. 2, 2015) – Scientists from Jiangxi Agricultural University, BGI and University of California published their latest research on genetic mechanism of pig altitude-adaptations in Nature Genetics.

Their research underlined the importance of introgression for the first time as a potential reason for pig adaptations to cold and hot environments, providing novel insights into the evolutionary history of pigs and the role of introgression in adaptation more generally.

Pigs, as one of the earliest domesticated animals, were domesticated largely in Near East and China approximately 10,000 years ago. Since then, under the combined effects of natural selection and human-driven artificial selection, pigs evolved phenotypic diversity in appearance, fertility, growth, palatability and local fitness.

To understand the genetic basis of the adaptation of the domestic Chinese pig to different latitudes and temperatures, researchers conducted a whole-genome sequencing and selective sweep analysis study.

They selected 69 pig individuals representing 11 geographically diverse breeds and three populations of wild boar from cold and hot environments in China. Each individual was sequenced at more than 20-fold depth with a genome coverage of 95 percent. In total, 41 million variants were identified, with 21 million variants that were previously not known. From the sequencing data, researchers constructed a nearly complete catalog of the genetic variants has been compiled, which allowed them to identify a genome-wide set of loci for local adaptation in Chinese pigs.

From the genome wide scan, a set of gene loci correspond to thermostatic regulation has been identified. Notably, an exceptionally large (14 Mb) and low-recombination region on the X chromosome appeared to have two distinct haplotypes in the high- and low-latitude populations, which may be possibly responsible for adaptations to cold and hot environments respectively.

Another surprising finding of this study was that the adaptive haplotype in the high-latitude populations was likely introduced from another divergent pig species. This is the first example of adaptive evolution triggered by interspecies introgression in domesticated animals, suggesting that introgression events between divergent species may be an important resource for evolutionary adaptation and could largely facilitate this process.

Mao Likai, the project manager of BGI, said, “We found lots of loci could be related with environmental adaptation. When we noticed a big region with special pattern on the haplotype figure of chromosome X, we knew something must be there.”

The article can be found at: Ai et al. (2015) Adaptation and Possible Ancient Interspecies Introgression in Pigs Identified by Whole-Genome Sequencing.


Source: BGI; Photo: Tim Strater/Flickr/CC.
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