“The expression of a large number of genes is regulated by alternative splicing. In human, for instance, recent studies have shown that this concerns 95 % of genes”, Patrick Motte explains. This alternative splicing is at the origin of the great diversity of proteins produced from a limited number of genes. “In the case of human, during the sequencing of the human genome, scientists were surprised to only find 30 000 genes. They found this to be very little considering the complexity of our organism. Indeed, the genome of the smallest flowering plant species also contains 30 000 genes... We now know that alternative splicing is the preponderant process leading to the great diversity of proteins”, continues the professor.

Retracing the evolutionary history of SR proteins

Whether it is constitutive or alternative, splicing requires a complex macromolecular edifice known as the spliceosome, which is itself composed of around a hundred different proteins. Among them are the SR proteins, whose name is derived from their domain rich in serine/arginine dipeptides. “The SR proteins participate in the assembly of the spliceosome, the selection of splicing sites and the inclusion or elimination of introns and exons in the mRNA”, Patrick Motte points out.

It is within the framework of the new research theme concerning alternative splicing, developed by Patrick Motte, that he began to focus on SR proteins. While he was working on these proteins, the scientist aimed to determine their origin over the course of evolution and, in particular, he wanted to know if they were present in all plants. “At my humble level, I started to compare and align several sequences of the green lineage (green algae and land plants) with a view to studying their evolution, but this quickly became very complex. That’s why I asked Professor Denis Baurain if he would be interested in working with me on this study”, explains Patrick Motte. 

Once contact was established, the researchers decided to do things on a large scale. Rather than limiting themselves to analysing the presence of SR proteins within the green lineage, they decided to research the presence of SR proteins on the scale of the tree of life! “We extended this study to numerous species whose proteome, i.e., the entire set of proteins, was already known at the time of the study”, specifies Patrick Motte. The idea was, among other things, to be able to answer the following question: were SR proteins already present in the last common eukaryotic ancestor?