In “Biochemistry: A Cold Editor Makes the Adaptation” (Science, February 17, 2012), Marie Öhman introduces an article that explains how life forms can live in very cold environments. Octopi and squid in particular, which adapt to tropics and poles, attracted research attention. It turns out that RNA gets edited to enable that, without changes in the genome sequence:
Although organisms have evolved to live in diverse conditions, closely related species often inhabit vastly different environments. This is particularly true for aquatic animals such as squid and octopus, which are common in tropical waters but are also found at the poles. These cephalopods have highly developed nervous systems, and one challenging question is how temperature-sensitive neuronal synaptic transmission has adapted to function at a near-freezing temperature. On page 848 of this issue, Garrett and Rosenthal (1) show that RNA editing rather than changes in the genome sequence enable potassium (K+) channels in octopus to function at different temperatures.
The abstract, “RNA Editing Underlies Temperature Adaptation in K+ Channels from Polar Octopuses” (Science 17 February 2012: Vol. 335 no. 6070 pp. 848-851
DOI: 10.1126/science.1212795) actually says they are “extensively edited” to enable a cold water switchover:
Abstract: To operate in the extreme cold, ion channels from psychrophiles must have evolved structural changes to compensate for their thermal environment. A reasonable assumption would be that the underlying adaptations lie within the encoding genes. Here, we show that delayed rectifier K+ channel genes from an Antarctic and a tropical octopus encode channels that differ at only four positions and display very similar behavior when expressed in Xenopus oocytes. However, the transcribed messenger RNAs are extensively edited, creating functional diversity. One editing site, which recodes an isoleucine to a valine in the channel*s pore, greatly accelerates gating kinetics by destabilizing the open state. This site is extensively edited in both Antarctic and Arctic species, but mostly unedited in tropical species. Thus adenosine-to-inosine RNA editing can respond to the physical environment.
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