Rest assured, they are still far from resurrecting the dinosaurs as in Jurassic Park, but these biologists have reached a great step forward to better understand the evolutionary mechanisms, especially that of the fruit fly!
Once upon a time, 140 million years ago …
Biologists have come to understand, in part, what happened 140 million years ago in Drosophila DNA. They have indeed discovered two mutations that would be responsible for the skull formation of our modern flies.
Described in the eLife review, this work was done using a revolutionary technique, successfully used for the first time in the research of embryonic development and evolution. Called “evo-devo”, this method consists in recreating an ancestral gene, first thanks to computer science, then developing it in the laboratory and implementing it in Drosophila embryos. Several versions of this gene have been created thanks to a protein called Bicoid.
Stephen Small, one of the authors of the study explained: “By introducing individual mutations that took place in the distant past inside these ancient genes, we were able to show precisely how each affected the development there. millions of years ago ”
Only two small mutations are responsible for a major change
Bicoid is actually a morphogen, that is to say, it determines the shape of the structures of an organism. Scientists have shown that without this gene flies die very quickly at the embryonic stage by forming two “tails” but no skull. Their job was to understand why and how this gene was able to evolve 140 million years ago. They then discovered two proteins responsible for the activation of the Bicoid morphogen, Stephen Small explains: “What is particularly interesting is that we show that two minor modifications of DNA sequences can redraw all the functions of the gene”.
To get into the details of their work, Stephen Small adds, “The function of the ancestral protein was to bind to a specific set of DNA sequences and activate a set of target genes based on that sequence.” ancestral protein to its modern descendants, the research team has identified two specific amino acid modifications that allow modern protein to bind to a completely different set of DNA sequences, compared to the ancestral protein. ] also showed that these modifications allowed the protein to activate a new set of target genes in the developing embryo and to acquire a central role in the embryogenesis of a subset of insect species. ”
A study that paves the way for other species
This study, which at present only focuses on the morphological formation of Drosophila, may well pave the way for the study of other species. In the meantime, researchers are still trying to identify each of the proteins that have played a role in the mutation of the genes of this little fly until we arrive at the one we know today.
Like 42,000-year-old nematodes found alive in Siberian permafrost, this study on the evolution of Drosophila shows that we are not at the end of our surprises!