30 November 2017
Camel DNA could unlock key to climate change adaptation
Published online 21 October 2014
Researchers analyse the DNA of different camel species to understand their evolution, hoping to uncover cures for common human disorders and to predict the effects of climate change.
An analysis of camel genomes, by Saudi and Chinese researchers, may help shed light on adaptation to climate change and the mechanisms behind diseases like asthma and diabetes.
The study, published in Nature Communications, is a collaborative effort between King Abdulaziz City for Science and Technology in Saudi Arabia (KACST), the Beijing Genomics Institute, and Inner Mongolia Agricultural University.
The researchers sequenced the genomes of the two-humped Asian camel, the single-humped Arabian camel, and one of their nearest relatives, the alpaca. They also sequenced the RNA of the Asian camel. The Arabian camel genome is the first mammalian genome to be sequenced in the Middle East.
“Camels have a significant impact on our economy [in Saudi Arabia] so we need research to improve camel breeds and their milk and meat yield,” says Abdulaziz Al-Swailem, vice president for scientific research support at KACST.
The Asian and Arabian camels live in extreme desert environments – making them ideal models for studying desert adaptations. They tolerate temperatures exceeding 40°C and water losses greater than 25% of their total body weight, extremes that would cause dehydration and death in mammals of other habitats.
The alpaca lives in the high altitudes of South America and does not exhibit the same adaptations to desert environments.
The researchers constructed an evolutionary tree based on 7,398 gene groups from ten species, including camelids (Bactrian Asian camel, dromedary Arabian camel, and alpaca). Their findings suggested the possibility of camel-specific evolution to adapt to desert environments.
They were also able to study historical rises and falls in camelid populations by analyzing the data of single-nucleotide polymorphisms: DNA variations that occur commonly within a population. Their data showed variations in population sizes that coincided with transitions between geological ages, periods of climatic changes, migrations across continents, and the dispersal of modern humans out of Africa and into Eurasia.
The researchers conducted a comparative analysis of the camelid genomes and all three camelids showed rapid evolution in genes related to the cellular response to insulin and in those related to energy, glucose, and fat metabolism.
Evolution and adaptation
We will sequence different varieties in Saudi Arabia and do comparative genomics within the Arabian camel species.
The two camels had an accelerated evolution in genes related to DNA damage and repair and immune responses. Compared to the alpaca, it was also evident that genes related to lung development had evolved rapidly, possibly allowing them to endure the respiratory challenges involved with airborne dust in desert environments.
Genes related to visual perception also showed rapid evolutionary development, suggesting a genetic basis for the camels’ ability to endure prolonged exposure to ultraviolet light without damaging their sight.
Differences in genes related to the transportation of sodium and potassium suggest camels may metabolize and transport salt more efficiently than alpaca and cattle. This is important for water reabsorption.
Further analysis indicates that camels are able to reabsorb water more efficiently in water-scarce conditions. Also, their ability to regulate sodium reabsorption may be essential for survival when water is scarce. It also seems that the characteristically high blood glucose levels in camels ensure enough energy to adapt to the effects of water restriction.
The identification of key genes involved in adaptation to desert environments may facilitate selective breeding to increase the proportion of camels with favorable genetic traits related, for example, to speed and milk yield.
Future studies on camel genomes and RNA may also contribute to a better understanding of the physiological mechanisms involved in some human medical conditions such as hypertension, diabetes, obesity and respiratory diseases.
Camels have a unique immune system that includes “nano-bodies”, special antibodies especially resistant to harsh conditions, explains Mohamed Al-Fageeh, manager and research associated professor at the National Center for Biotechnology at KACST. A deeper understanding of this system through genome sequencing can help develop new human vaccination approaches and improved antibody therapies. Understanding the molecular mechanisms involved in the very high blood sugar levels of camels could pave the way for the development of therapies for diabetes, he adds.
The researchers also believe camelid genomes could be useful for studying biological adaptations to climate change.KACST funded this research and was involved in the sequencing of the Arabian camel genome. “Our next step is to sequence more camels,” says Al-Fageeh. “We will sequence different varieties in Saudi Arabia and do comparative genomics within the Arabian camel species.”