How Octopi Can Edit Their Own RNA to Rapidly Respond to Environmental Changes

 Organisms have multiple ways that they change their gene expression in response to stimuli. For example, an octopus thats suddenly put into frigid water can slow their enzyme activity. Some organisms can control their genetic responses to stimuli in another way, RNA editing. RNA editing involves the insertion and deletion of nucleotides in the RNA and has been visualized in mRNAs, tRNAs, rRNAs. It has not been yet visualized in prokaryotes. RNA editing is divided into two categories. One categories being insertion and deletion of nucleotides that changes the length of the target DNA. The second category is editing by base modification that changes a nucleotide into a different nucleotide, without changing the length of the RNA. The article describes how cephalapods, octopi, squid, and cuttlefish can change their mRNA in ways that can alter enzymes. Since the edits are in RNA and not DNA, they can go away quickly. The nucleotide adenine in the mRNA is replaced with inosine, a nucleoside that acts similar to guanine. This RNA edit can be known as "A-to-I RNA editing" and if it occurs in a protein, it alters its function. Finding out what the cephalopods use this RNA editing for was the big question. Researchers tested this by using the California two-spot octopus, which cannot generate its own body temperature, and placed both captive and wild octopi in tanks of 13 degress celcius. In these tanks, the researchers observed an increase in 13,285 mRNAs where the edited genes altered the proteins functions. When placing the animals back into warmer water of 22 degrees celcius, the amount of mRNAs decreased to 550. These RNA edits affected their nervous system and the scientists could hypothesize that the octopi were using these gene edits to cope with the change in temperature.