Molecular Domestication of TLEWI DNA Transposons: Evidence and Contradictions.

Transposable elements (TEs) are found in the genomes of almost all eukaryotes. They have a characteristic structure that ensures their transposition activity, as a result of which TEs can make changes in the structure and functioning of the genome. Through coevolution with the genome, TE sequences can be domesticated. "Molecular domestication" refers to the cooptation of a TE sequence, as a result of which it begins to perform a useful function in the host genome. In bivalves, DNA transposons of the TLEWI subfamily have been identified, which have signs of domestication, as well as spliceosomal introns, which makes them similar to eukaryotic genes. To test the domestication hypothesis, this work carried out an intraspecific analysis of the presence of TLEWI transposons in the Pacific oyster (Crassostrea gigas) and their transcriptional activity in various tissues, during ontogeny and under the influence of internal and external factors. As a result, intraspecific heterogeneity was revealed in the presence of potentially functional copies and expression of transposase genes. For example, for two elements, a dependence of transcriptional activity on the stages of ontogenesis, as well as on temperature, was revealed. This suggests that functional (possibly domesticated) alleles have been conserved in individual populations of the Pacific oyster. The accumulation of additional data will allow us to discover populations that retain active TLEWI transposase genes and to determine whether these genes have been domesticated by the genome. [ABSTRACT FROM AUTHOR]