Vol 53, No 5 (2017)

Keratoconus (KC) is the most common form of keratoectasia characterized by changes in corneal topography and its thinning, stretching, and protrusion. The hereditary or genetic theory of keratoconus development is widely recognized. To date, a large number of candidate genes have been investigated in patients with KC. One of the most important of them are the gene encoding a homeodomain-containing protein that belongs to the subfamily of paired-like homeodomain proteins (VSX1), superoxidedismutase 1 (SOD1) gene, and the gene of lysyloxidase (LOX). The linkage analysis reveals over 17 chromosomal regions mutations in which can lead to the development of KC. In families with a hereditary form of keratoconus by GWAS analysis, the association of central corneal thickness (CCT) with a number of genetic loci is revealed. Thus, diverse results of genetic studies and a large number of identified chromosomal regions associated with keratoconus, firstly, show marked genetic heterogeneity of the disease and, secondly, are associated with challenges in DNA diagnosis of this disease. However, there are prerequisites that keratoconus belongs to both hereditary and genetically caused diseases and identified genetic variants are specific both to individual populations and to certain ethnic groups in general.

A comparison of amino acid sequences is performed for orthologs to the meiosis-specific proteins in humans and seven other species, including animals, fungi, and plants that serve as models for the study of molecular mechanisms of meiosis. It is demonstrated that the RAD51 recombination mediator protein is the most conserved of the studied proteins. Its meiotic homolog DMC1 is less conserved, like the MHL1 mismatch-repair protein. The meiosis-specific SPO11 endonuclease is the least conserved among the studied meiotic enzymes. Structural proteins of meiotic chromosomes are poorly conserved. REC8 meiotic cohesin has 6 times lower similarity in the organisms from different kingdoms than its somatic homolog RAD21. The intermediate conservation level is characteristic of the synaptonemal complex proteins containing HORMA domain. Two functional domains of SPO11 endonuclease and MutL Trans_MLH1 domain of MLH1 enzyme are equally or even less conserved than the whole proteins. HORMA functional domain of a number of synaptonemal complex proteins is only 2–3 times more conserved than the whole molecule. Thus, among the key meiotic proteins, the most conserved are proteins responsible for the accuracy of meiotic recombination. Cohesins, synaptonemal complex proteins, and meiosis-specific SPO11 endonuclease are less conserved even within their functional domains. Obviously, the meiosis-specific proteins have undergone independent evolution in different phylogenetic lineages of eukaryotes.

Comparative molecular genetic study of Williopsis yeasts isolated in different world regions reveals some peculiarities of species content in Taiwan. Some Williopsis yeasts may represent novel species. In Taiwan, four of the five known Williopsis species are documented: W. saturnus, W. suaveolens, W. mrakii, and W. subsufficiens. The W. saturnus yeasts predominate in Taiwanese soils, while W. suaveolens is more frequently isolated in Europe.

To evaluate genetic variation, 27 accessions of allotetraploid species Aegilops kotschyi and Ae. variabilis with the US genome were analyzed using the AFLP, RAPD, and ISSR methods. A total of 316 polymorphic RAPD fragments, 750 polymorphic AFLP fragments, and 234 polymorphic ISSR fragments were obtained. It was demonstrated that the analyzed species were characterized by a considerable level of nuclear genome variation. According to the data of ISSR and RAPD analysis, the average value of the Jaccard similarity coefficient for the accessions of Ae. variabilis from different geographical regions was slightly lower than that for the accessions of Ae. kotschyi. At the same time, AFLP analysis showed no considerable differences in the levels of intraspecific variation of the studied species. Analysis of the summarized RAPD, ISSR, and AFLP marking data in the Structure software program showed that most of the analyzed accessions with high degree of probability could be assigned to one of two groups, the first of which corresponded to Ae. kotschyi and the second corresponded to Ae. variabilis, thereby confirming the species independence of Ae. kotschyi and Ae. variabilis. Accessions k900, k907, k908, and v90 could not with a sufficiently high degree of probability be assigned to one of the species, which possibly was the result of interspecific hybridization. Analysis of the species diversity using different molecular markers made it possible to identify the accessions that were notably different from other accessions of its species.

The objectives of conservation and sustainable forest management require in depth study of genomes of woody plants and definition of their intraspecific genetic diversity. In recent years, an approach was developed based on the study of “candidate genes” that can potentially be involved in the formation of adaptive traits. In this study, we investigated nucleotide polymorphism of several adaptive candidate genes in the populations of Siberian larch (Larix sibirica Ledeb.) in the Urals. Representatives of this genus are among the most valuable and widely distributed forest tree species in Russia. From ten selected gene loci in the genome of L. sibirica, we isolated and investigated three loci, one of which (ABA-WDS) was sequenced in L. sibirica for the first time. The total length of the analyzed sequence in each individual amounted to 2865 bp. The length of locus alignment was from 360 bp to 1395 bp. In total, we identified 200 polymorphic positions. The most conservative is locus 4CL1-363, and the most polymorphic is locus sSPcDFD040B03103-274. The studied populations of L. sibirica are characterized by a high level of nucleotide polymorphism in comparison with other species and genuses (Picea, Pinus, Pseudotsuga, Abies) conifers plants (Hd = 0.896; π = 0.007; θ_W = 0.015). The most selectively neutral polymorphism (D_T =–0.997) was attributed to locus 4CL1-363, and polymorphism with high probability of adaptability (D_T =–1.807) was determined for the ABA-WDS locus. We identified 54 SNP markers, only five of which were nonsynonymous (9.26%) replacements. The average frequency of SNPs in the three studied loci of L. sibirica was one SNP in 53 bp. We detected unique SNP markers for eight populations, which could potentially be used to identify populations. Populations that are characterized by the highest number of unique SNP markers can be recommended for selection in order to preserve the gene pool of the species.

Baikal endemic Benedictia fragilis gastropods distributed in a wide range of depths (from sublittoral to abyssal) of three lake basins are studied. The analysis of the nucleotide sequence of the COI mitochondrial gene fragment and internal transcribed nuclear DNA spacer (ITS1) demonstrates that the studied gastropods are represented in Lake Baikal by three genetic groups. The results of the studies on genetic diversity, phenotypic traits, and distribution allow us to assume that the detected groups are incipient allopatric (geographical) species. On the basis of the data obtained and geological and climatic history of Baikal, possible pathways of the B. fragilis resettlement in the lake and the emergence of three genetic groups are hypothesized.

The variability of the mtDNA locus COI in the Florida crab (Rhithropanopeus harrisii) of coastal populations of the northern Black Sea is studied. The introduction of this crab species is demonstrated to originate from European populations, most likely the Netherlands. The studied populations experienced a strong decline in the level of genetic variability based on the haplotype diversity, but to a lesser extent based on the nucleotide diversity. Analysis of the structure of decapod community of Crimea makes it possible to discuss the reasons underlying invasive success of the Florida crab in the region.