Sheep genome cracked, spotlights rumen evolution

After eight years of work, researchers have completed the first sequencing of the entire sheep genome.

Scientists have cracked the genetic code of sheep to reveal how they became a distinct species from goats around four million years ago.

The study is the first to pinpoint the genetic differences that make sheep different from other animals.

The findings could aid the development of DNA testing to speed-up selective breeding programs, helping farmers to improve their stocks.

The International Sheep Genomics Consortium — compared the sheep's genes with those of other animals — including humans, cattle, goats and pigs.

The analysis identifies several genes that are associated with wool production. It also reveals genes that underpin the evolution of the rumen.

This collaborative study, involving 26 research institutions in eight different countries, was led by researchers from the Commonwealth Scientific & Industrial Research Organization in Australia; BGI and the Kunming Institute of Zoology in China; Utah State University and Baylor College of Medicine in the U.S., and The Roslin Institute in the U.K.

Professor Alan Archibald, head of genetics and genomics at The Roslin Institute, said, "Sheep were one of the first animals to be domesticated for farming and are still an important part of the global agricultural economy. Understanding more about their genetic make-up will help us to breed healthier and more productive flocks."

The research identifies the genes that give sheep their fleece and uncovers features of their digestive system, which makes them so well-suited to a diet of low quality grass and other plants.

It also builds the most complete picture yet of sheep's complex biology. Further studies using this resource could reveal new insights to diseases that affect sheep.

"We investigated the completed genome to determine which genes are present in a process called gene annotation, which resulted in an advanced understanding of the genes involved in making sheep the unique animals that they are," CSIRO project leader Dr Brian Dalrymple said.

"Given the importance of wool production, we focused on which genes were likely to be involved in producing wool. We identified a new pathway for the metabolism of lipid in sheep skin, which may play a role in both the development of wool and in the efficient production of wool grease (lanolin)."

Min Xie, Project Manager from BGI, said, "Sheep is an important livestock with great economical value to provide people with meat, milk and fine wools. The availability of sheep genome provides us an opportunity to investigate the genetic basis of the rumen evolution and lipid metabolism in sheep skin. Based upon the genomic data in this study, more and more sheep-related studies could be conducted for expanding our understanding on this livestock. It also facilitates the maker-assisted selection for high-quality traits such as wool, meat, milk, among others."

Sheep are also an important biomedical model, particularly in Australia, and the genomic resources built by the team will provide a strong foundation for the detailed exploration of the similarities and differences between sheep and humans at the molecular level, and hopefully lead to improved medical treatments for a number of conditions such as sepsis and asthma.

The study is published June 5 in the journal Science.

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