Studies Shows That One Gene ” Reinvented” Haemoglobin Several Times.
Thanks to the marine ragworm Platynereis dumerilii, an animal whose genes evolved very slowly, a group of scientists has shown that although haemoglobin appeared independently in several species, it actually comes from a single gene passed down to all of their last common ancestor.
The results of the study, conducted by scientists from CNRS, the University of Paris and the Sorbonne University, together with other universities in St. Petersburg and Rio de Janeiro, were published in the journal BMC Evolutionary Biology.
Having red blood is not peculiar to humans or mammals.
This color comes from haemoglobin, a complex protein specialized in transporting oxygen found in the vertebrate circulatory system, as well as from pectorals (a family of worms, the most famous representatives of which are earthworms), mollusks (especially pond snails) and crustaceans (such as daphnia or “water fleas”).
It was thought that in order for haemoglobin to appear in such diverse species, it had to be “invented” several times during evolution.
However, recent studies have shown that all of these haemoglobins, born “independently,” actually come from the same ancestral gene.
Researchers from the Institut Jacques Monod (CNRS/Universite de Paris), the Maternal and Systems Laboratory Complex (CNRS/Universite de Paris), the Roscoff Biological Station (CNRS/Sorbonne Universite), St. Petersburg (Russia) and Rio de Janeiro (Brazil) universities conducted this study on Platynereis dumerilii, a small sea worm with red blood.
This animal is thought to have evolved slowly because its genetic characteristics are close to those of the marine ancestor of most animals, Urbilateria.
Studying these worms by comparing them with other species with red blood has helped trace the origin of haemoglobin.
Research has focused on the broad family to which haemoglobins belong: globins, proteins present in almost all living things that “store” gases such as oxygen and nitric oxide.
But globins usually act inside cells because they do not circulate in the blood like hemoglobin.
This work shows that in all species with red blood, it is the same gene that makes a globulin called “cytoglobin,” which has independently evolved to become haemoglobin, encoding hemoglobin.
This new circulating molecule made oxygen transport more efficient in its ancestors, which became larger and more active.
Now scientists want to change the scale and continue this work by studying when and how different specialized cells of bilateral vascular systems came into being.