Leiden biologists sequence first two snake genomes
Leiden biologists Freek Vonk and Michael Richardson have sequenced the first two snake genomes, of the king cobra and the tiger python. They published their findings on 2 December in two articles in leading journal PNAS.
The genome is the complete collection of genetic material in a cell. The research indicates that the king cobra is continually having to evolve to outwit its prey, that over time builds up resistance to the snake venom. 'There is an evolutionary conflict going on between the snake and its prey, so the snake is under pressure to make sure its venom works ever more rapidly and effectively,' Vonk explains.
The researchers discovered that there are proteins in the complex snake venom that are important in capturing the prey, and that are under enormous pressure from natural selection. The research also shows that the venom genes in the evolutionary past were used in other places in the snake's body (such as in the stomach, heart, liver, blood cells and reproductive organs).
Genes that do not normally have a venomous function can be 'switched on' in the venom gland. This often takes place at the same time as the duplication of a particular gene, which means that both continue to exist and the copy is used in the venom gland. But sometimes a non-venomous gene is hijacked by the poison gland. In both cases, such a protein can develop over time to become venomous. 'Our results give a unique insight into the evolution of one of the world's most advanced natural bioweapons,' says Vonk.
The findings from this research can contribute to the development of new medicines. They also offer starting points for developing vaccines against snake bites, that cause 150,000 deaths every year.
The other article in PNAS describes the genome of the Indian python, a large constrictor snake native to Southern Asia. Vonk and Richardson have also worked on this research, that is being led by scientists from the University of Colorado (USA). The genome of the Indian python shows that this giant snake switches on particular genes directly after eating, so that organs that aid digestion (heart, liver and small intestine) temporarily increase in size. This is necessary because these giant snakes sometimes eat only a few times a year.
The prey of these snakes is often very large, sometimes 50 per cent of the snake's own body weight. To be able to handle food of this size, snakes have developed a range of physical adaptations: a moveable skull, flexible jaws, skin that is highly elastic and free-floating ribs. But there are also adaptations built into the genome. Directly after the snake has eaten, the cells of the organs expand and, once the prey has been digested, the cells shrink back to their normal size. The heart, for example, can expand by as much as 50 per cent.
To map the genetic structures of the king cobra, Vonk and Richardson worked with ZD Screens, run by Leiden Professor Herman Spaink, and Baseclear, a company located in the Leiden Bio Science Park. In total, scientists from 15 different institutes are involved in the project.
The journal Science will also focus attention on these two research projects on 7 December 2013, devoting a major article to Freek Vonk and his career as a researcher and TV presenter.
(3 December 2013 - W&N)
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