Genome complexity: modifying RNA controls of genes (Introduction)

by David Turell , Friday, April 07, 2017, 15:10 (2575 days ago) @ David Turell

In cephalopods there are RNA editing sites that control the genetics, not seen so far in other parts of the bush of life:

http://www.the-scientist.com/?articles.view/articleNo/49153/title/Cephalopod-Genomes-Co...

"RNA editing sites are rarely found in the coding regions of most animals’ genomes. But according to a study published today (April 6) in Cell, the genomes of squid, octopus, and cuttlefish contain hundreds of thousands of editing sites, many of which are found in coding regions and are evolutionarily conserved.

"The authors showed that recoding events—in which RNA’s adenosine (A) is post-transcriptionally converted to inosine (I), resulting in incorporation of a new amino acid—are often adaptive and contribute to diversity in the animals’ proteomes. And sequence conservation of regions surrounding editing sites has slowed down genome evolution in behaviorally complex coleoid cephalopods.

"Coleoid cephalopods “change the amino acid code, so you have a big diversification of the proteome, which you don’t see in any other animals,” Marie Öhman, who studies RNA editing in the mammalian brain at Stockholm University in Sweden and did not participate in the work, told The Scientist. “That it’s so extensive is really amazing.”

“'When we started looking into this we really didn’t know if this massive recoding was more of a bug or more of a feature,” said coauthor Noa Liscovitch-Brauer, a postdoc at Tel Aviv University in Israel. “What we show here is that it is probably advantageous, and this is something special that only they do.”

"Most organisms have very few functional [editing] sites in coding regions,” said coauthor Eli Eisenberg of Tel Aviv University. “This is why we find it so unusual and surprising that in squid, octopus, and cuttlefish, we see exactly the opposite.”

***

"The team found evidence of positive selection in genomic regions immediately adjacent to editing sites. These regions had fewer mutations than sequences far from editing sites. And because there are so many editing sites and thus sequences under positive selection, the cumulative constraints have slowed down coleoid genome evolution.
 
“'There are lots of [editing] sites that are highly conserved between octopus and squid,” coauthor Joshua Rosenthal of the Marine Biological Laboratory in Woods Hole, Massachusetts, told The Scientist. “They’re going so far as to dampen genomic evolution in order to maintain it.” (my bold)

“'The editing is very pervasive, particularly the recoding events,” said Jin Billy Li, who studies RNA editing at Stanford University in Palo Alto, California, and was not involved in the study. “It’s a striking finding, but it’s also a first step. There are just so many questions to ask . . . How does this happen? And what’s the functional consequence?”

***

“'The cephalopods will offer a gold mine in terms of understanding the mechanisms that they’ve adopted to generate this [behavioral] complexity,” said Rosenthal. “I’m certainly not suggesting that editing is the only answer. I think it’s part of the equation, and I think looking how organisms solve problems differently is invaluable.'”

Comment: Note my bold. This appears to be a mechanism to sustain current phenotypes, not advancing evolution in this group. This is opposite to the recent report on how human evolution proceeded: Wednesday, March 08, 2017, 18:54, which was not seen in the rest of the primate group. From the report:

"'This paper lifts the lid off something that had been largely unsuspected: the tremendous species-specific dimension of human gene regulation", says Trono. "It has profound implications for our understanding of human development and physiology,"(my bold)

This suggests that genome controls complexity is broadly different across the bush of life. If common descent is true, the genome mechanisms should be similar across the bush. Since it isn't perhaps God is actively seen to be monkeying with the works. This seems to be direct evidence of dabbles!