A genetic engineer himself

Octopuses have edited their own genes

Anna Manshina, N+1

Israeli scientists have discovered that octopuses and their relatives from the subclass of diptera actively edit their own RNA for better adaptation to the environment. This ability is an alternative to the traditional gene expression model, it slows down the genome change, but makes cephalopods smarter. An article about the study was published in the journal Cell (Liscovitch-Brauer et al., Trade-off between Transcriptome Plasticity and Genome Evolution in Cephalopods).

The stages of gene expression, the process by which functional proteins and RNA are built according to the genetic "blueprint" of DNA, are well known. First, an intermediate information carrier, mRNA, is synthesized on the DNA matrix. Then, on the basis of the ribosome mRNA, proteins are collected. The transmission of information occurs without loss and changes, the sequence of amino acids in the protein exactly corresponds to the order of nucleotides in the gene that encodes it, and the diversity of proteins in the body arises due to their further modifications.

Much less often, mRNA modification occurs, it is carried out by enzymes from the ADAR family (adenosine deaminases of RNA), which convert the nucleotide adenosine into inosine. Such a change allows you to fine–tune the functions of proteins, but it is used quite rarely, in humans there are about three percent of the altered RNA, and in drosophila - from one to four percent. However, the authors of the current study found out in previous papers that octopuses use this modification to adapt to temperature changes.

In the new work, scientists decided to find out how often and for what octopuses use mRNA editing. To do this, they analyzed the DNA and RNA of cephalopods from all branches of the evolutionary tree: the developed two-gilled (octopus, cuttlefish, squid) and the more primitive nautilus, as well as the gastropod mollusk aplysia, as a control representative of another class.

To detect cases of RNA editing, scientists have found systematic inconsistencies between DNA and RNA. They found about one hundred thousand edited RNA sections in the two–gilled ones, and only a thousand in nautilus and aplysia. To find out how actively modified RNA is involved in the creation of proteins, scientists analyzed the proteome of the octopus brain. It turned out that about 60 percent of its proteins were created on the basis of edited RNA, including proteins that are responsible for connecting neurons in mammals. The researchers suggested that it is RNA editing that allows the two-gilled to use complex behavioral scenarios.

The scientists also noted that the modification of RNA significantly slows down the evolution of the two-gilled, because it is very sensitive to DNA mutations. Any mutation can close the possibility of protein editing and deprive octopuses of some important feature for survival.

It turns out that octopuses preferred excellent adaptability and very high intelligence for invertebrates at the moment to the usual evolutionary path that led to the appearance of, for example, mammals. 

Octopuses are generally very smart. They are able to seep into the cracks of a complex shape, threaten each other with color, use very complex camouflage for defense and attack, and use jellyfish as hunting tools.

Portal "Eternal youth" http://vechnayamolodost.ru  10.04.2017