Genetics of the oyster is decrypted

Gene data provide an explanation for the adaptability of the sea shell

This oyster has just been caught fresh in the Pacific off the Chinese Qingdao. © Guofan Zhang, photo by Tao Liu
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An international research group has sequenced the genome of the oyster. This was the first time that the genome of a mollusc species, including shells and snails, was completely decoded. DNA analysis shows that the oyster genome carries a particularly extensive set of genes that allow marine animals to adapt to different environmental conditions. Oysters, for example, have survived severe temperature fluctuations, changes in salinity or even toxic heavy metals, the researchers report in the journal Nature.

The scientists also found that the formation of the shell shell is far more complex than previously thought. In addition to their current findings, the genome decryption finally help to further investigate the evolution of the mollusk hole, say the scientists.

Mostly grown on rocks in the surf area, the oyster can not easily escape changes in their environment. Affected by high tide and low tide, the mussel must master strong temperature fluctuations or different salt concentrations of the seawater. To better understand their enormous adaptability, Guofan Zhang from the Qingdao Chinese Academy of Sciences and his colleagues sequenced the genome of the oyster species Crassostrea gigas, which is widely distributed in the Pacific. The genome of mollusks, which include mussels and snails, is still under-researched, the researchers explain. Using the oystercorn DNA analysis, they hope to gain further basic knowledge about the evolution of this group of animals. Because the mollusks play an important role in the conservation of the ecosystem. Clams, for example, filter fresh and salt water and clean up the world's water resources.

For their study, it was not enough to sequence the genome of a mussel. Because initial experiments showed that in oysters especially many genes have different characteristics, the researchers write. This also occurs in humans. For example, there are genes for eye color which may be brown, blue or green. In order to include these different gene variants in the oyster, the researchers analyzed the genome of four clam generations of the species Crassostrea gigas.

The oyster species Crassostrea gigas originally comes from the Pacific in northern Asia and has penetrated as far as the Dutch Wadden Sea. Roger man

Using their genes, oysters can withstand up to 49 degrees Celsius

The sequencing revealed that the genome consists of 28, 027 genes. Of these alone 5, 844 are involved in the adaptation to different environmental conditions, the researchers report. They found that out when they recorded the activity of each gene sequence, while exposing it to nine different stressors such as temperature, salinity, air, or heavy metals. Most of these antistress genes, a total of 4, 420, responded to exposure in the air. This suggests that air is the main stress factor for oysters, the researchers conclude. display

Upon exposure to heat, the activity increased from a total of 88 genes, which are known to adapt to extreme temperatures. In comparison, humans would only have 17 of these genes. This explains why oysters endure heat spells of up to 49 degrees Celsius when exposed to direct sunlight at low tide, the researchers say.

In order to protect themselves from the sun or predators, oysters also have a particularly thick mussel shell made of lime. So far, it has been thought that these are mainly developed using silk-like proteins that attach themselves to each other and form the shell structure. However, the scientists did not find any genes that provided the blueprint for this type of molecule. The formation of a shell is much more complex, with probably a whole set of different proteins working together, the biologists suggest. (Doi: 10.1038 / nature11413)

(Nature, 20.09.2012 - IRE)