Vol 53, No 12 (2017)

The nematode C. elegans is a classic study object of developmental biology and genetics, which is particularly suitable for studying the molecular bases of meiosis. Developing meiocytes are located in the threadlike gonads of C. elegans in linear gradient order of the stages of meiosis, which facilitates studying the order of intracellular events during meiosis. C. elegans has polycentric chromosomes. This causes a special order of events during meiosis, and as a consequence, meiosis in C. elegance differs from canonical meiosis of most eukaryotes. In the meiotic prophase I, all chromosomes carry single protein “pairing centers.” They are responsible for joining homologous chromosomes in pairs. This initiates the formation of synaptonemal complexes (SCs). Programmed double-stranded DNA breaks appear after initiation of the SC assembly, and they give rise to meiotic recombination. The initiation of meiotic recombination after the chromosome pairing distinguishes the C. elegans meiotic pattern from those in the absolute majority of eukaryotes studied. C. elegans has strict crossing over interference, which allows for the formation of one chiasma per bivalent. In the late prophase I, the polycentric centromeres are remodeled, one of the chromosome ends acquires a cuplike kinetochore, and during two meiotic divisions, chromosomes behave as monocentric. The study of meiosis in C. elegans allows for separate investigation of synapsis and recombination of homologous chromosomes and provides material for studying the evolution of meiosis.

Mutations in the white locus emerged in highly mutable isofemale Drosophila melanogaster lines from the populations of Novosibirsk 2013 (NS3 line), Nalchik 2014 (N119 line), and Sakhalin Island 2014 (S46 line). A single white-eyed male found in the NS3 line was sterile. Phenotypically mutant derivatives (white gene alleles) differing in eye color (pure white, different shades of yellow (honey), orange (apricot), cherry, and red (wild type)) emerged during the N119 and S46 line breeding in the laboratory. Molecular genetic study of the structure of wild type white locus in initial lines and white-mutant derivatives de novo emerging from them, as well as other white lines from the fund of the Laboratory of Population Genetics of the Institute of Cytology and Genetics (Siberian Branch, Russian Academy of Sciences), was conducted. The pairs of primers flanking different white gene regions were selected. Six such pairs overlapped the coding part of the gene. Molecular genetic analysis demonstrated that most DNA defects were limited to the region which includes the first exon (34 lines). Among them, four mutant events were accompanied by an insertion of DNA fragments of approximately 800 bp; one mutation event was accompanied by a deletion of approximately 200 bp; in 29 cases, no PCR product was obtained (this can indicate that as a minimum one of the primer binding sites is damaged). The inserted DNA fragments have no homology with known D. melanogaster sequences presented in the NCBI database. The complete white gene deletion with the manifestation of mutant “white eyes” phenotype was registered in four cases (and only in the N119 line derivatives). Normal PCR product was obtained in 22 cases for all six DNA fragments. Among them, there are both alleles phenotypically mutant by the eye color (white, cherry, or orange) and revertants to the wild type (red). The abundance of defects in the beginning of the gene can indicate a multiplicity of mobile genetic element insertion sites in this part of the white gene in D. melanogaster.

Earlier, in the wheat Triticum kiharae Dorof. et Migusch., a new family of genes coding for the hevein-like antimicrobial peptides WAMPs, involved in the protection of wheat plants against pathogens, was discovered. In the present study, we examined the wamp homologs in plants belonging to ten di-, tetra-, and hexaploid species of the genus Aegilops L., among which there are donors of polyploid wheat genomes, as well as of the resistance genes to the most important wheat pathogens. Using PCR amplification with genomic DNA as a template and primers specific to the sequences of the wheat wamp genes, for the first time, nucleotide sequences of the protein-coding regions of wamp homologs were determined in the species of the genus Aegilops L. The wamp homologs were found in all species studied. It was demonstrated that the WAMP peptide precursors encoded by them differed in single nucleotide substitutions, as well as deletions/insertions of amino acid sequences. The most conserved region of the precursor is the mature peptide region, where, in addition to the variable position 34, deletions of amino acid sequences were found in a number of peptides. To elucidate the role of deletions in the antimicrobial activity of WAMPs, a recombinant WAMP-3 peptide with a deletion in the N-terminal region was produced by expression in E. coli cells, and it was shown that antimicrobial activity of the peptide was preserved. It was demonstrated that all the discovered wamp genes were expressed in seedlings of the studied Aegilops species. The results shed new light on the structural diversity of genes encoding the hevein-like antimicrobial peptides WAMPs.

Larix kaempferi is an economically and ecologically valuable afforestation and timber species. However, functional genes participating in its growth and development remain largely unknown because of its long growth cycle and highly complex genetic background. In this study, LkAP2L2, an AP2/ERF transcription factor gene, was identified and the characteristics and functions of LkAP2L2 were further explored. The cDNA of LkAP2L2, with a length of 2124 bp, encodes a transcription factor comprising 707 amino acid residues. LkAP2L2 was further introduced into Arabidopsis genome using the Agrobacterium tumefaciens transformation method. The shoot branching phenotype of LkAP2L2-overexpressing Arabidopsis was enhanced. The number of their branches was almost twice as high as that of the vector control plants. In contrast to those on bushier branches, the size and number of rosette leaves were decreased by LkAP2L2 overexpression. In particular, the length of the fifth rosette leaves was shorter by approximately 17% in 35S::LkAP2L2 plants, and the number of rosette leaves was approximately 70% of that of the vector control. In addition, the length of silique was decreased by a half compared with the vector control plants, and no more than 4 seeds per silique were detected in the transgenic plants. The length of siliques and the number of seeds are decreased by LkAP2L2 through its influence on flower development. Therefore, LkAP2L2 of L. kaempferi plays a crucial role in branch, flower, silique and seed development, and this gene may be manipulated to obtain the bushy phenotype of plants.

Genetic and morphological analysis of endemic sponges of the Lubomirskiidae family from Lake Baikal and the upper reaches of the Angara River was performed. Various sponge species acquired a number of similar morphological traits after the transition from the lake into the river. These traits enabled an increase of sponge skeleton strength under the conditions of elevated hydrodynamic activity. The changes significantly impeded morphology-based species identification of Angara sponges. Phylogenetic analysis of ITS regions and noncoding mitochondrial DNA fragments confirmed that the Angara sponges belonged to the Baikalian Lubomirskiidae family and demonstrated the polyphyletic origin of the sponges. The use of combined molecular and morphological data allowed for the clustering of some sponge samples into groups that corresponded to individual species. The absence of genetic isolation between the Baikalospongia intermedia and Lubomirskia baicalensis species was demonstrated, whereas the B. intermedia profundalis subspecies was well separated from B. intermedia. This finding pointed to the necessity of further studies for the clarification of the taxonomic status of this subspecies.

The Tc1/mariner superfamily is one of the most widely distributed among the DNA transposons in both terrestrial and aquatic organisms. We studied the abundance of the Tc1/mariner elements in the genome of the gastropod Littorina saxatilis Olivi, 1792 (Gastropoda: Littorinimorpha). For this purpose, nucleotide sequences with a total length of 358877 bp were analyzed. Six sequences were found to be similar to the Tc1/mariner DNA transposons. These sequences were studied for structure, the presence of functional transposase, and the systematic position within the superfamily. In addition, the loci with high homology to the DNA transposons of the hAT, Sola, Ginger, EnSpm/CACTA, ISL2EU, Kolobok, Novosib, Zisupton, and Helitron superfamilies were identified.

Examination of the sex ratio (SR, male to female ratio) among carriers of Robertsonian translocations (rob) in newborns in the general population has not previously been given due attention, probably because of focusing on the striking female preponderance among fertile women explained by sterility of male carriers. Meta-analysis of published studies on 68,212 newborns showed differences in SR depending on the type of rearrangements: there were similar rates of male and female reciprocal translocation carriers (34♂/33♀, 0.97 and 0.99‰, correspondingly), but female preponderance among carriers of rob, regardless of their parental origin was observed (27♂/41♀, 0.77 and 1.24‰, correspondingly). Similar results were obtained from the prenatal cohort. Collectively, among carriers of rob with known parental origin, there were 66♂ and 97♀ (SR = 0.68), different from the expected ratio of 1: 1, p = 0.0093; for carriers of reciprocal translocations and inversions a typical slight male prevalence was found. Female-biased SR was demonstrated for carriers of the most frequent rob, t(13;14), with 50♂/85♀ (SR = 0.59, p = 0.0016), but not for carriers of other robs (28♂/27♀, SR = 1.04). A mechanism of female-specific rescue of translocation trisomy, due to loss of maternal chromosome, resulting in female preponderance among carriers of balanced translocations, along with reciprocal male preponderance among carriers of unbalanced translocations, could explain the observed phenomenon. Both female-biased SR among carriers of balanced 45,der(13;14),upd(14) with 4♂/12♀ and malebiased SR among carriers of unbalanced 46,+13,der(13;14) with 16♂/2♀, support the proposed hypothesis.

Karyotyping of the common shrews Sorex araneus from the poorly studied region of the Northwest of Russia revealed the belonging of individuals to two chromosomal races, Lemi and St. Petersburg. The Lemi race, previously known only from Finland, was discovered for the first time on the territory of Russia and thus replenished the list of S. araneus chromosomal races that are distributed within the Russian part of the species range (27 races out of 74 known in the whole species range at the moment). The studied individuals showed a high level of chromosomal polymorphism, caused by Rb translocations.