ANALYSIS OF DIVERGENCE OF ALPHITOBIUS-DIAPERINUS SATELLITE DNA - ROLES OF RECOMBINATION, REPLICATION SLIPPAGE AND GENE CONVERSION

Satellite DNA is highly abundant in Alphitobius diaperinus (Tenebrioni dae, Coleoptera), comprising 25% of the total genomic DNA. Sequence an alysis reveals an average GC content of 50.8% and the presence of thre e different groups of satellite monomer variants, tH1, tH2 and tH3 wit h corresponding lengths of 123, 128 and 126 bp. Their mutual homologie s range between 65 and 81%. Sequence comparison shows that the monomer variant tH2 has been formed by a recombination process between tH1 an d tH3, which have a low average homology of only 65.15%. The longest s tretch of 100% homology between the recombining units is 17 bp and is located 3' to the predicted recombination site. There is also an indic ation from sequence analysis that replication slippage and gene conver sion play a part in the formation of satellite units and contribute to their divergence. The tH1, tH2 and tH3 monomer variants are organized in higher order repeating structures: a dimer, composed of tH1 and tH 3, and a trimer containing tH1, tH2 and tH3 in series. The dimeric and trimeric repeat units furthermore create three higher order satellite subfamilies. Two of them contain either tandemly arranged dimers or t rimers, while the third one is composed of both types of repeats, mutu ally interspersed.