Influence of Various Factors on the Transcription Activity of Pogo Transposons in the Pacific Oyster Crassostrea Gigas

Transposable elements (TE) are a ubiquitous component of eukaryotic genomes. The genomes of different organisms contain different combinations of elements. TE are divided into retrotransposons and DNA transposons depending on the structural organization and mechanism of movement. One of the most common groups of DNA transposons is the pogo superfamily. Ten pogo transposons have been described in the genome of the Pacific oyster Crassostrea (Magallana) gigas (Thunberg, 1793). In this paper, it was shown that the pogo oyster elements belong to three families: pogoR, Passer and Fot, although there is a possibility that the Mariner-30_CGi element may represent a new evolutionary group in the superfamily. Analysis of the genomes of five oyster individuals showed that the presence of nine pogo elements is detected in all individuals, one element (Mariner-38_CGi) was found in only two genomic assemblies. The studied genomic assemblies showed differences both in the number of copies of pogo transposons, and in their length and also the presence and length of inverted repeats. However, in most cases, the differences identified are not fundamental. Data on the evolutionary dynamics of pogo transposons and a low number of copies in the genomes of individual individuals indicate low activity throughout the life cycle. The analysis of transcriptional activity revealed that the elements Mariner-30_CGi and Mariner-34_CGi showed constant or condition-dependent expression in more than half of the cases. Transcriptional activity was revealed in five elements, depending on the stages of development. It is assumed that these elements could have been domesticated (co-opted) by the oyster genome. This study expands our understanding of the evolution of pogo transposons and their role in the diversification of animal genomes.