Octopuses and other cephalopods are among the most intelligent invertebrates, capable of complex tasks such as solving puzzles. But their brains are very different from ours, with elaborate nervous systems stretching throughout their bodies and working in amazing ways that scientists are only beginning to understand.
For example, cephalopods have an unparalleled ability to edit their RNA, molecules that provide essential functions such as transferring information and building proteins. A new one A study published in the journal Go Two species of octopus found off the coast of Southern California (USA) describe how large sections of their RNA can be modified in response to sudden changes in temperature.
Certain RNA changes affect the proteins made in the nervous system, and the changes help everything run smoothly when conditions change. Those proteins are very sensitive to temperature fluctuations; Too hot or too cold, and its efficiency decreases. A change of a few degrees can be fatal. This is especially a problem for cold-blooded animals like the octopus, which are at the mercy of their environment’s will to regulate temperature.
“Water is a very cruel substrate to live on,” he says Joshua Rosenthal, a neuroscientist at the Marine Biological Laboratory in Woods Hole, Massachusetts, led the new study. “It’s a real challenge to think at different temperatures. Nervous systems are very complex.”
(Related: This octopus defends its place by throwing objects and is hunted)
A variety of animals, from squids to squirrels to humans, are known to recode their RNA. These natural changes alter the messages that genes send, subtly altering the molecules used to make proteins. But the changes are not permanent.
Rosenthal and other researchers previously found that cephalopods are unusually capable of pulling this genetic trick. While there are hundreds of known “editing sites” in the genomes of humans, there are tens of thousands in cephalopods. Scientists began to study what benefits such widespread but temporary fixes would bring to the species.
Acclimatization, or adaptation to new environmental conditions, is an “obvious hypothesis,” says Rosenthal. Having the ability to edit RNA on the fly would allow animals to optimize proteins in the nervous system and elsewhere based on ambient temperature. It’s an idea that scientists have been considering for a long time, but there’s no evidence at the molecular level.
To see if this biological rewiring could be captured in action, Rosenthal and his colleagues focused on two well-studied proteins: kinesin, which transmits important cellular material, and synaptotagmin, which is important for transferring signals between neurons. They chose to study Octopus pimaculoidesIt’s commonly known as the California two-spot octopus because it has a well-ordered genome and naturally lives in a wide range of temperatures (and, unlike other octopus species, because it cools down when transported to the lab, Rosenthal adds).
To test directly whether sudden changes in temperature increase RNA editing, the researchers placed octopuses in tanks and allowed them to acclimate for two to three weeks. Then they changed the temperature to 13 or 22°C at 10 to 12 days and maintained it for another 12 to 24 days.
Next, the researchers extracted RNA from the animals’ stellate ganglia, a part of the nervous system responsible for motor control, and examined how many RNA sites were edited under different environmental conditions. Even accounting for cephalopods’ ability to rewrite RNA, the results surprised the researchers. Most of the editing occurred within hours of the temperature change and was gone within four days.
“It was amazing,” Rosenthal says. “We expected a small number of sites to be temperature sensitive, maybe none. But about a third of them are temperature sensitive.”
(Related: Does this octopus that changes color in its sleep have nightmares?)
As scientists study how octopuses restructure their RNA in response to changes in temperature, they can also investigate what benefits this genetic tool gives the animals when they move to the ocean.
“They seem to be doing something unique with this, which is giving them a way to flexibly respond to their environment,” he says. Kavita Rangan, a molecular biologist at the University of California, San Diego, was not involved in the study. Rangan’s own work was discovered Recently similar temperature-driven RNA editing, another cephalopod. “Editing is a mechanism that can generate a lot of protein variation, and some of that variation may be adaptive.”
A clue may be that octopus RNA editing was more extensive when the animals were in colder environments. In the heating experiment, only about one percent increased, a result that may seem negative at first glance.
“Typically, enzymes are overheated. It’s just thermodynamics,” says Rosenthal. “Here we see more correction in the cold.” Perhaps the corresponding molecular structures are more stable at cold temperatures and therefore easier to modify, but further testing is needed to confirm this.
“It’s clear that the organism does something very important to adapt to temperature, but it’s very difficult to assess the functional consequences of this version,” he says. Jin Billy Ltd, a geneticist at Stanford University who was not involved in the study. “There are a lot of questions to ask from here, but this is very important and interesting work.”
