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Stress-induced genes identified in corals

Editor: zhangrui 丨Xinhua

03-13-2017 07:55 BJT

SAN FRANCISCO, March 12 (Xinhua) -- Marine biologists at Stanford University have discovered that corals activate a specific group of ancient, defensive genes when exposed to stressful environmental conditions.

By monitoring three coral colonies in a lagoon on Ofu Island, American Samoa, for their response to stressors like high temperatures, oxygen, and ocean acidity, the researchers saw a significant change in which genes the corals were activating within their cells.

These stress-induced genes could serve as a kind of warning sign for coral bleaching events.

Under stressful conditions, a coral's normal cellular functions begin to fail. In response, the group of genes identified in this study triggers a process, called the unfolded protein response, that works to restore normal conditions within the cell. If conditions continue to worsen, the corals bleach and eventually die.

Over the course of the seventeen-day study, Steve Palumbi, a professor of marine sciences and an author of a paper published in the latest issue of Science Advances, together with graduate student Lupita Ruiz-Jones, monitored over 17,000 coral genes at just after noon each day.

On the seventh and eighth day, when tides were lowest and temperatures hottest, the corals' genes initiated the cellular unfolded protein response. On day nine, the tides rose and the corals' systems returned to normal.

"For the first time, we are able to ask those corals, 'how are you doing?' They don't have a heartbeat. They don't have a pulse. We need to know their vital signs in order to understand how they react to the environment," Palumbi was quoted as saying in a news release from Stanford.

The lagoon on Ofu Island, a shallow turquoise bathtub, provided the ideal coral laboratory for studying heat-tolerant corals. The corals on Ofu experience water temperatures near human body temperature, enough to kill most coral species. However, they prosper in stressful environmental conditions.

Scientists believe that frequent, pulsing exposure to high temperatures may make corals stronger, much in the same way athletes train for competition. Understanding why some of the world's toughest corals are so heat-tolerant could help scientists identify and map other survivor coral colonies around the globe.

The stress response has been observed in mammals as well as some yeast species. Humans activate the same ancient genes in response to diseases, like cancer.

In times of stress, a cell's misfolded and unfolded proteins accumulate in the endoplasmic reticulum, a series of flattened, tube-like structures in the cell that assist with building proteins. The unfolded protein response is a reaction to the flood of misassembled proteins.

"It's basically the organism recognizing that something isn't right," Ruiz-Jones said.

In the corals' case, Palumbi said, "they started using a whole set of genes that they had just not been using before."

 

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