Temperature savvy
Evolution exploits editing
The nervous system of this warm water-dwelling Octopus vulgaris functions smoothly thanks to edits in the animals' RNA.
The frigid waters of the Southern Ocean don't slow Antarctic octopuses down, even though their nervous systems are governed by the same genetic instructions as their tropical counterparts. Now scientists know why: Edits to the creatures' genetic instructions tweak the octopuses' nerve cells for smooth operating in the numbing polar waters. The discovery is the first report of such editing actually helping an organism adjust to its environment, scientists report online January 5 inScience. Because nerve cells can't send signals as quickly in the cold, scientists decided to compare genes fromPareledone, an octopus that lives in the icy waters off Antarctica, with those of the warm-water species Octopus vulgaris. To the researchers' surprise, the genetic instructions were pretty much the same. "It was a real disappointment at first," says molecular neurobiologist Joshua Rosenthal of the University of Puerto Rico Medical Sciences Campus in San Juan. "We thought there was going to be a difference in their genes, but they were basically identical. It was puzzling." Rosenthal and graduate student Sandra Garrett figured something must alter the way the DNA instructions are relayed to and interpreted by the body's nerve cellbuilding machinery. DNA always stays put in the nucleus of cells, and sections of it are copied when instructions for functioning or building parts are needed. So the researchers looked at this genetic photocopy, the mRNA. It turns out that an enzyme that specializes in editing mRNA alters the blueprints for the octopuses' nerve cells in both polar and tropical species, the researchers discovered. The mRNA edits slightly change the way that nerve cells open and close gates to produce electrical impulses. In the Antarctic octopus species, the edits speed up the closing of one gate, while in the tropical species, the edits make that gate close more slowly. Because cold slows the gates down, these editing tweaks nicely counteract the effects of temperature and keep the gates in sync with other parts of the nervous system.
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