MicroRNAs are evolutionarily older than previously thought
MicroRNAs are evolutionarily older than previously thought
Microorganisms close to animals have animal microRNAs, according to a study with participation of the Institute of Evolutionary Biology (CSIC-UPF) (Spain). Published in Current Biology, reveals that microRNAs, small sequences that regulate the activity of genes, are not unique to animals. Several Ichtiosporea, microorganisms that live mainly in marine environments, have animal microRNAs without being themselves animals.
A microorganism in which animal microRNA has been found without being an animal itself is Sphaeoforma arctica (pictured). It has been isolated from the stomach of a small Arctic crustacean (Gammarus setosus), but no one knows yet if it is a parasite or if the crustacean had eaten it. " SEM microscope image taken by Arnau Sebé-Pedrós (Multicellgenome Lab / IBE (CSIC-UPF).
Scientists have long sought to discover what happened in evolution so that single unicellular organisms end up transforming into more complex multicellular organisms, like animals. Among other things, they look for what genetic elements made a difference, opening the way to greater genetic and morphological complexity.
One of these elements are microRNAs, very small pieces of RNA that regulate the activity of other genes, silencing or activating them.
A microorganism in which animal microRNA has been found without being an animal itself is Sphaeoforma arctica (pictured). It has been isolated from the stomach of a small Arctic crustacean (Gammarus setosus), but no one knows yet if it is a parasite or if the crustacean had eaten it. " SEM microscope image taken by Arnau Sebé-Pedrós (Multicellgenome Lab / IBE (CSIC-UPF).
All animals have microRNAs except Ctenophora, marine organisms similar to jellyfish. Until now it was thought that the microRNAs, and the genes involved in their formation (among them, Pasha and Drosha) were an exclusive innovation of the animals because they had not detected microRNA (or their genes) in unicellular organisms phylogenetically closest to animals .
Now, a work with participation of the Institute of Evolutionary Biology, mixed center of the CSIC and the UPF, and published in the journal Current Biology, denies that hypothesis and says that both the microRNAs and the genes Pasha and Drosha arose before the appearance of the animals. The work is led by researchers from the University of Oslo (Norway).
Iñaki Ruiz-Trillo, ICREA researcher at the Institute of Evolutionary Biology, mixed center of the CSIC and Pompeu Fabra University, and co-author of the work, explains that until now it was thought that the acquisition of microRNA was key to the origin and evolution of the animals - "the plants also have, but they are of another type", he clarifies. "In fact, previous studies in which coanoflagellates had been studied, unicellular organisms close to animals, revealed that these organisms have neither microRNA nor the genes to produce them."
In the work published this week, scientists have performed a genetic analysis of other unicellular organisms close to animals, organisms such as Capsaspora, an amoeba that parasitic snails, or the Ichthyosporea, a group of protists that live, above all, in environments marine The results reveal that different species of Ichthyosporea have animal-like microRNAs, as well as the genes that process them.
This means that "the unicellular ancestor of animals was already able to regulate the expression of some genes by means of microRNA, as current animals do," says Ruiz-Trillo, who is also an associate professor at the University of Barcelona.
One of the microorganisms that have animal microRNA without being animal itself is Sphaeoforma arctica. As a curiosity, Ruiz-Trillo explains "that he was isolated from the stomach of a small Arctic crustacean (Gammarus setosus), but no one knows yet if it is a parasite or if the crustacean had eaten it."
The results fit with recent findings, largely by the same team of Ruiz-Trillo. "In recent years we have seen that the unicellular ancestor that gave rise to animals was genetically quite complex, both in genes and in processes of gene regulation and genomics," concludes the researcher. (Source: CSIC)
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