From Wired:
But when Stanford University geneticist Jin Billy Li heard about Joshua Rosenthal’s work on RNA editing in squid, his jaw dropped. That’s because the work, published today in the journal Cell, revealed that many cephalopods present a monumental exception to how living things use the information in DNA to make proteins. In nearly every other animal, RNA—the middleman in that process—faithfully transmits the message in the genes. But octopuses, squid, and cuttlefish (but not their dumber relatives, the nautiluses) edit their RNA, changing the message that gets read out to make proteins.
In exchange for this remarkable adaptation, it appears these squishy, mysterious, and possibly conscious creatures might have given up the ability to evolve relatively quickly. Or, as the researchers put it, “positive selection of editing events slows down genome evolution.” More simply, these cephalopods don’t evolve quite like other animals. And that could one day lead to useful tools for humans.
From the paper itself:
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.
Or that not having a reliable site-identifying motif is a bit of a bummer.
A Popular Science article on the paper:
But they still don’t know how to make myelin sheaths.
Then again, apparently neither did the cephalopods’ designer.
Glen Davidson
I wonder how a cephalopod changes its pattern of RNA editing without making any change in its DNA. Leprechauns?
Leprechauns move in mysterious ways, don’t ya know.
Glen:
One designer didn’t tell the other. Don’t listen to the monodesignist heretics.
I wondered that, too. But I think this is the fault of the press release perhaps. I emailed Dr Rosenthal asking whether he was suggesting a violation of the central dogma but he replied:
At first glance, RNA editing might seem a violation of the central dogma. But the enzymes that are doing it are themselves encoded in DNA.
ADARs are the enzymes that edit RNA. They edit specific adenosine residues. In order to do so, they require complex surrounding structures in the RNA. The enzymes recognize and bind to these structures before they can edit—and the structures are often 100’s of nucleotides long. If an ocotpus and a squid want to edit the same adenosine, then the underlying structure had to be preserved during evolution. This means that I can’t have accumulated mutations. We show that RNA editing sites are conserved across large evolutionary distances and the mutation rates around the RNA editing sites are depressed. In cephalopods, there are lots of conserved RNA editing sites so there is a lot of the coding sequence with depressed mutations rates.
Looks like trap door evolution.
How about this analogy: If I misspell a few words in a paragraph, most people can still read it. But if I misspell a decryption key, I can lose everything.
So the sequences that code for the editor are highly conserved.
Evolutionarily conserved is an oxymoron.
If an ocotpus and a squid want to edit the same adenosine, then the underlying structure had to be preserved during evolution.
And if the ocotpus and the squid don’t want to edit the same adenosine?
Mung,
If you truly believe that, then you might benefit from some RNA editing in your own brain tissues.
None of this RNA editing stuff seems to square well with PZ Myers
http://freethoughtblogs.com/pharyngula/2017/04/07/cephalopods-are-natural-born-editors/
http://freethoughtblogs.com/pharyngula/2017/04/07/the-worst-take-on-that-cephalopod-rna-editing-story-yet/
http://freethoughtblogs.com/pharyngula/2017/04/09/aaargh-its-like-watching-the-spread-of-a-plague/
Edit: Posted in wrong thread.
Pet peeve of mine: confusing mutation rates with fixation rates. He really means the latter.
Rumraket,
It’s the press coverage he has a problem with, not the RNA editing.
Yeah that’s what I meant, thanks for the correction. An important distinction.
ENV’s inevitable (and laughable) take on this research:
It’s uncredited. Who writes this stuff?
And some idiot at the DI chose to take metaphor literally in order to score cheap points.
Sorry, Evolution New and Views, that’s hardly news.
Glen Davidson
Iwoud argue that “choose” has pretty much the same meaning in both cases.
The difference is that the DI buffoon thinks it has a choice.
Glen Davidson
John,
Apparently some things are too stupid even for a DI flack to take “credit” for.
I would argue that consciousness is irrelevant to the question of choice..