EVOLUTION OF GYPSY-GROUP RETROTRANSPOSONS - PHYLOGENETIC ANALYSIS OF POL-POLYPROTEIN DOMAINS

Transposons of gypsy group are assigned to LTR-containing retrotranspo sons present in the genomes of invertebrates, fungi, and plants. In th is work, a theoretical analysis of the potential products of ORFs of t hese retrotranposons was conducted. Alignments were obtained and trees of similarity were constructed for domains of the POL region. On the basis of the obtained data, two hypothetically monophyletic subgroups of transposons were distinguished within the framework of the gypsy gr oup, settling the genomes of taxonomically related organisms (the subg roup of ''true'' gypsy of insects and the subgroup of gypsy-like tranp osons of plants and fungi). A number of peculiarities of the topology of these trees hypothetically indicate cases of genetic conversion and recombination of domains accompanying the evolution of this group. Th e amino acid substitution fixation rate was evaluated on the basis of comparison of sequences of the protein products of ORFs. Estimates of the time of divergence of subgroups of gypsy-group transposons are sig nificantly less than estimates of the times of divergence of their hos t species. One explanation for this discrepancy might be the hypothesi s of settlement by transposons of the genomes of isolated host species .