Photo courtesy of Wang Xiaolong, Tibetan goat
Known as the “Third Pole of the Earth”, the Tibetan Plateau has created a unique biodiversity due to its extreme environment of cold, low oxygen, low pressure and strong ultraviolet rays. Along with human migration and production activities, a group of domesticated animals have gradually adapted to the harsh ecological conditions of the Qinghai-Tibet Plateau, and have become indispensable means of production and subsistence for residents in Tibetan areas.
Recently, professors Wang Xiaolong and Jiang Yu of Northwest A&F University, and Han Jianlin, a researcher at the Chinese Academy of Agricultural Sciences-International Livestock Research Institute, and other units collaborated to discover a new selected gene PAPSS2 in the genome of Tibetan goats. The gene originated from the gene infiltration of a wild relative species of goats in the Himalayas, an ancient gene infiltration event that helped goats quickly adapt to the harsh natural environment of the plateau. The findings were published in Molecular Biology and Evolution.
Goats quickly adapt to the harsh environment of the Qinghai-Tibet Plateau
With an average altitude of more than 4,000 m, the Qinghai-Tibet Plateau is the highest plateau in the world. Despite the unique geographical environment, early humans living on the plateau domesticated and domesticated animals including yaks, Tibetan cattle, Tibetan sheep, Tibetan goats, Tibetan pigs, Tibetan chickens, Tibetan horses and Tibetan mastiffs, and these livestock and poultry resources provided important means of production and subsistence for local herders.
Wang Xiaolong introduced that due to the natural barrier, goats traveled from Central Asia all the way east to the cold Qinghai-Tibet Plateau about 3,000-5,000 years ago, although this time was later than the time when goats migrated to Europe and East Asia, but goats adapted to the harsh and harsh natural environment of the plateau in a short time, and the reason behind them became the direction of scientific research.
Han Jianlin told China Science News that about 11,000 years ago, goats were successfully domesticated by ancient humans in the Fertile Crescent (today’s two river basins in West Asia and North Africa). As the origin of the ancient Lianghe civilization, the land is fertile, the climate is pleasant, and it has the innate conditions for the development of agriculture and animal husbandry, giving birth to the world’s first domesticated animals and plants such as goats, sheep, pigs, barley and wheat. With human migration, these species now reach all corners of the world, and in the process, animals need to try to adapt to a variety of differentiated environments, including the heat of the equatorial region and the cold hypoxia of the plateau.
How do goats migrating from low altitudes to plateaus adapt to the harsh environment of cold, low oxygen, low pressure and strong ultraviolet rays on the Qinghai-Tibet Plateau, the “third pole of the earth”?
“Analyzing the genetic mechanism of the adaptation of plateau livestock to extreme environments can not only reveal the interaction mechanism between plateau environment and genetic diversity, but also contribute to the mining, protection and utilization of existing plateau livestock and poultry genetic resources, and provide theoretical basis and technical support for the genetic improvement of plateau livestock.” Wang Xiaolong explained.
Look for the root cause of goat adaptation
In order to find the root cause of goats’ adaptation to the harsh environment of the Qinghai-Tibet Plateau, Wang Xiaolong, with the encouragement and support of team leader Professor Chen Yulin, cooperated in-depth with the Tibet Academy of Agriculture and Animal Husbandry, and led the team to enter Tibetan areas four times and collected genetic materials and tissue samples of more than 10 goat breeds in Tibet.
“We have cooperated with Jiang Yu’s team and other units to collect genomic data of multiple goat populations around the world, especially the application of third-generation long fragment sequencing technology to help us find genomic information that has not been discovered by previous technical means.” Wang added.
They first analyzed data from 331 genomes and 104 transcriptomes of domestic goats, wild goats, and ancient goats distributed at different altitudes around the world, and used PacBio HiFi data to assemble a chromosome-level reference genome of Tibetan goats. After locating the key selected gene PAPSS2, the project team also used the team’s mature CRISPR/Cas9 method to further verify the function of the PAPSS2 gene in cells.
Finally, the project team used the largest goat genome data obtained so far to reveal that the PAPSS2 gene is not only the most critical gene for goats to adapt to high altitude, but also the most significant gene in gene infiltration analysis, which proves that the ability of Tibetan goats to adapt to plateau comes from gene ingression from multiple levels.
Jiang Yu explained that gene exchange is a common cross-species or inter-population genetic phenomenon in nature, which plays an important role in the adaptive evolution of domestic animals. Gene inflection refers to the fact that the hybrid offspring of two species or populations can transfer or graft certain traits of one parent to another group through repeated backcrossing with their parents, specifically involving the transfer and integration of some genes of one species or population to the genome of another species or population.
Gene introgression can break the original reproductive isolation between species or groups, thereby generating and maintaining genetic diversity within the group, promoting its rapid adaptation and evolution, and then forming new populations and even species, promoting the spread of species, and playing an important role in the process of biological evolution.
Further analysis showed that the haplotype of the PAPSS2 gene of Tibetan goats was highly consistent with that of the kudu goat, which was mainly distributed in the Himalayas and its surrounding high-altitude areas. The kudu goat is Pakistan’s “national treasure” animal, with fewer than 3,000 individuals in existence.
A series of analyses showed that this infiltration was caused by interspecific hybridization of the kudu goat, and that this infiltration was only present in the genome of high-altitude goats and was not detected in nearly 20 goat breeds derived from Chinese mainland.
excavateHighland livestock genetic resources
“This study systematically evaluates the genetic resources of Tibetan goats at the genome-wide level, reveals the genetic mechanism of Tibetan goat plateau adaptation, and further confirms that gene infiltration between wild relatives plays a very important role in the rapid adaptation of livestock to extreme environments.” At the same time, the research results have very important guiding significance for the mining, protection and genetic improvement of plateau livestock genetic resources. Wang Xiaolong said.
Different plateau areas in the world have been settled by humans, animals and plants, but their adaptation mechanisms to the plateau environment are very different, and the highland populations in various places have experienced different adaptive changes in the long-term evolution and adaptation process.
For example, the Andean population adapts by improving the ability of each red blood cell to carry oxygen, while Tibetan compatriots in China effectively compensate for the lower oxygen content in the air by increasing the number of breaths.
A similar phenomenon exists in animals. Some animals have gained a place through long evolution, tapping their genetic potential to adapt to harsh environments; Others adapt quickly by communicating genes with closely related species.
In contrast, Wang Xiaolong believes that gene infiltration from “close relatives” is the most direct and rapid way to survive. In the Qinghai-Tibet Plateau, genetic infiltration has adapted to the plateau environment for a long time, and studies have shown that gene exchange was widespread between ancient Tibetans and Denisovans, Tibetan sheep and pan sheep, Tibetan mastiffs and Tibetan wolves, and Tibetan cattle and yaks. As a result of gene exchange, highaltitude animals are better adapted to local extreme environments.
The Qinghai-Tibet Plateau is one of the regions with the highest concentration of biodiversity, species diversity and genetic diversity in the world, and is a natural treasure trove, so it is of great significance to realize the conservation and strategic application of the resources of the Qinghai-Tibet Plateau.
According to Wang Xiaolong, due to various conditions, many livestock and poultry genetic resources distributed in plateau ravines, snowy mountains, deserts and deep forests have yet to be thoroughly investigated and excavated. It can be expected that the ongoing third national census of livestock and poultry genetic resources will make full use of the theories and methods of modern genomics and genetics to unearth a number of excellent new genetic resources for livestock and poultry. Through further germplasm creation and cultivation of new varieties, it will have great and long-term significance for fighting the battle of turning over the seed industry and promoting the revitalization of the seed industry. (Source: China Science News, Li Chen, Yang Yuan)
Related paper information:https://doi.org/10.1093/molbev/msac253