How the evolution of genomes leads to the current diversity of life remains a central question in Biology. Some of the most puzzling genomic innovations are triggered by transposons. Transposons are mobile genetic elements (DNA sequences) that can jump within a genome. They are characterized by DNA motif repeats at both ends of their sequence (interspersed repeats) and were considered for long only as parasitic DNA elements or ‘junk’ DNA. However, recent evidence have demonstrated their role in adaptive evolution through several mechanisms. Nevertheless, most of transposons have no or a negative impact on host organisms and are therefore counter-acted by several host pathways, such as DNA methylation and PIWI-interacting RNAs (piRNAs). piRNAs are small RNAs that bind to transposons and are part of a protein complex which cut down transposons, disabling their ability to jump within genomes and producing more piRNAs (feedback loop). The recent advances in technologies, both sequencing techniques (long-read sequencing) and computational resources (Machine Learning / Artificial Intelligence), allow now to precisely categorize transposons. TEEPI is set to take advantage of those new technologies to understand the role of transposons in the emergence of phenotypic innovations. TEEPI is also set to understand the evolutionary dynamics of transposons with host defense mechanisms and its impact on the emergence of novel and complex phenotypes. To that end, both transposons and piRNAs are studied simultaneously to precisely understand their interactions.
In order to unravel the role of transposons, along with their evolutionary dynamics with host piRNAs, in the emergence of novel phenotypes, TEEPI focus on the evolution of the insect order Blattodea, which encompasses cockroaches and termites. Those insects were chosen as model system, since they have repeatedly evolved complex phenotypes, such as eusociality in termites (a Major Evolutionary Transition and the highest level of sociality) and wood feeding. Furthermore, only few blattodean species have been sequenced so far (3 cockroach and 6 termite species) and demonstrates that a large part of their genome is made up of transposons. This enhances the potential of TEEPI to bring groundbreaking results and to rely mostly on genomes obtained with long-read sequencing technology, hence allowing a precise categorization of transposons and piRNAs. In addition, several cockroach and termite species are common pests and responsible for billion of euros of damages to human societies, which warrant the need of a better characterization of their resilience and biology at the molecular level to efficiently manage them without hindering other valuable insect species. More precisely, TEEPI focus on the categorization and mapping of transposons and piRNAs within blattodean genomes, to unravel their role during termite eusocial transition.
