[Phylogenetic relationships among holarctic populations of Chironomus entis and Chironomus plumosus in view of possible horizontal transfer of mitochondrial genes]. / Filogeneticheskie vzaimootnosheniia golarkticheskikh populiatsii Chironomus entis i Chironomus plumosus s uchetom vozmozhnoi gorizontal'noi peredachi mitokhondrial'nykh genov.

In eight Holarctic populations of two typical chironomid sibling species of the plumosus group, Chrionomus entis and Chironomus plumosus, nucleotides sequences of mitochondrial (cytb) and nuclear (gb2b) gene regions were examined. The phylogenetic trees reflecting the evolutionary histories of the nuclear and mitochondrial markers exhibited significant differences. On the tree based on the nuclear gene sequences the populations clustered according to their species affiliation, whereas on the tree based on the mitochondrial gene sequences the populations were grouped according to their geographic position. This discrepancy is probably explained by mitochondrial gene flow between sympatric species with incomplete reproductive isolation (sibling species). Based on our results together with the earlier data on nuclear and mitochondrial gene sequences of some other species from the phylogenetic group plumosus, a scheme of phylogenetic relationships within this group is proposed. This scheme is in many ways different from the traditional view on the evolutionary relationships among species of the plumosus group.

[Headcase gene--proliferation or hormonal control?]. / Gen headcase--proliferatsiia ili gormonal'nyi kontrol'?

A new insertion allele of the hdc gene was isolated and described. The nucleotide sequence of the coding region had no detectable homology with genomic DNA of any other Drosophila species, except for D. mauritiana. Gene expression was found both in adult testes and ovaries and at embryonic and larval stages. This expression pattern exhibits a strong similarity to that of cell-cycle genes. In contrast to cycE (a typical cell-cycle gene), which leads to expression termination after in vivo culturing of the wing disk, hdc did not arrest expression. It is concluded that hdc is a species-specific differentiation gene, whose regulatory activity in the development of an organism differs from that of proliferation genes.