Genome complexity: modifying RNA controls of genes (Introduction)

by David Turell , Friday, March 08, 2019, 20:43 (1876 days ago) @ David Turell

Another review on the same subject:

https://www.cell.com/cell/fulltext/S0092-8674(17)30344-6

"Unlike other taxa, cephalopods diversify their proteomes extensively by RNA editing
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Extensive recoding is specific to the behaviorally complex coleiods
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Unlike mammals, cephalopod recoding is evolutionarily conserved and often adaptive
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Transcriptome diversification comes at the expense of slowed-down genome evolution

"Summary

RNA editing, a post-transcriptional process, allows the diversification of proteomes beyond the genomic blueprint; however it is infrequently used among animals for this purpose. Recent reports suggesting increased levels of RNA editing in squids thus raise the question of the nature and effects of these events. We here show that RNA editing is particularly common in behaviorally sophisticated coleoid cephalopods, with tens of thousands of evolutionarily conserved sites. Editing is enriched in the nervous system, affecting molecules pertinent for excitability and neuronal morphology. The genomic sequence flanking editing sites is highly conserved, suggesting that the process confers a selective advantage. Due to the large number of sites, the surrounding conservation greatly reduces the number of mutations and genomic polymorphisms in protein-coding regions. This trade-off between genome evolution and transcriptome plasticity highlights the importance of RNA recoding as a strategy for diversifying proteins, particularly those associated with neural function."

Another discussion:

https://www.sciencealert.com/it-s-official-octopus-and-squid-evolution-is-weirder-than-...

"It's true that coleoid cephalopods are exceptionally intelligent. There are countless riveting octopus escape artist stories out there, not to mention evidence of tool use, and that one eight-armed guy at a New Zealand aquarium who learned to photograph people. (Yes, really.)

"So it's certainly a compelling hypothesis that octopus smarts might come from their unconventionally high reliance on RNA edits to keep the brain going.

"There is something fundamentally different going on in these cephalopods," said Rosenthal.

"But it's not just that these animals are adept at fixing up their RNA as needed - the team found that this ability came with a distinct evolutionary tradeoff, which sets them apart from the rest of the animal world.

"In terms of run-of-the-mill genomic evolution (the one that uses genetic mutations, as mentioned above), coleoids have been evolving really, really slowly. The researchers claimed that this has been a necessary sacrifice - if you find a mechanism that helps you survive, just keep using it.

"The conclusion here is that in order to maintain this flexibility to edit RNA, the coleoids have had to give up the ability to evolve in the surrounding regions - a lot," said Rosenthal.

"As the next step, the team will be developing genetic models of cephalopods so they can trace how and when this RNA editing kicks in.

"It could be something as simple as temperature changes or as complicated as experience, a form of memory," said Rosenthal."

Comment: An amazing side branch on the bush of life. They have ganglions of neurons in each leg helping to run the show in each leg.