Cold Edits

by Dr. Elizabeth Mitchell on January 14, 2012

Science: “Octopuses Rewrite Their RNA to Beat the Cold Why the octopus doesn’t have to come in from the cold

Puerto Rican neurophysiologists puzzling over how polar organisms “evolved structural changes to compensate for their thermal environment”1 have been surprised and delighted to discover the secret of the Antarctic octopus and its Arctic cousins.

Originally hypothesizing that polar organisms were genetically different from their tropical relatives, Dr. Joshua Rosenthal and Sandra Garrett discovered a “whole different molecular mechanism for increasing protein diversity.” Their paper published in the January 5 edition of Sciencexpress “sets the stage for showing that RNA editing can have a big role in adaptation.”

Nerve conduction is normally hampered by frigid temperatures. Protein channels in nerve cell membranes—channels that allow ions to move in and out of nerve cells—do not reset to their closed positions very well in the cold. Since Antarctic octopuses thrive in freezing water, Rosenthal said, “We thought we were going to see changes at the level of the gene”—figuring the cold-loving animals had evolved to genetically produce a channel protein with better cold-performance.

When they sequenced the gene coding for the channel protein in both Antarctic and tropical Puerto Rican octopuses, they found the genetic codes were virtually identical.

When they sequenced the gene coding for the channel protein in both Antarctic and tropical Puerto Rican octopuses, they found the genetic codes were virtually identical. They even inserted the gene sequences into frog eggs and confirmed the proteins produced behaved the same way. Therefore, they concluded the Antarctic octopus must somehow edit the messenger RNA after transcription in order to build a better protein for the cold.

Further testing confirmed octopus messenger RNA is consistently altered so that a different amino acid is inserted at several places in the protein. One of the substitutions in the Antarctic octopus, at site I321V, “more than doubled the rate of closure”2 of the channel protein, allowing the channel to close quickly even in the cold.

To confirm the importance of the I321V substitution for cold adaptation, the team tested two Arctic species, two more tropical ones, and two temperate ones. Editing at the I321V site was a prominent finding in the Arctic species, but not the others.

Rosenthal concludes, “This process can be used to help adapt to the environment.” Exactly how and “whether octopuses use editing for rapid acclimation or long-term adaptation”3 is as yet unknown.

Despite the researchers’ assertion that “RNA structures that drive editing evolve and generate species-specific patterns,”4 there is no evolution of new kinds of animals involved in this study. RNA editing does not build new kinds of creatures but it does allow a way for creatures to vary within their created kinds. The octopus design at the molecular level already has in it the information required to adapt to the cold by varying this necessary protein’s structure. God created all kinds of creatures fully functional about 6,000 years ago. This research reveals one way He equipped the octopus to adapt.


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Footnotes

  1. www.sciencemag.org/content/early/2012/01/04/science.1212795
  2. Garrett, S. and J. Rosenthal. 2012. “RNA Editing Underlies Temperature Adaptation in K+ Channels from Polar Octopuses.” Sciencexpress. DOI: 10.1126/science.1212795.
  3. Garrett, S. and J. Rosenthal. 2012. “RNA Editing Underlies Temperature Adaptation in K+ Channels from Polar Octopuses.” Sciencexpress. DOI: 10.1126/science.1212795.
  4. Garrett, S. and J. Rosenthal. 2012. “RNA Editing Underlies Temperature Adaptation in K+ Channels from Polar Octopuses.” Sciencexpress. DOI: 10.1126/science.1212795.

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