Vol 53, No 7 (2017)

Unreduced gametes play a fundamental role in speciation of flowering plants, asexual reproduction of plants, and restoration of fertility of distant hybrids used to produce new varieties with breeding-valuable traits. Unreduced gametes are formed as a result of meiotic restitution. To date, a large body of data has been accumulated on the types of meiotic restitution in dicots and monocots. However, there is no clear idea on the cytological mechanisms of this process. In this review, we systematize and analyze all currently known mechanisms of restitution in plants. New data on the mechanisms and genetic regulation of unreduced gamete formation in intergeneric wheat hybrids are presented.

Many bacteria belonging to the order Rhizobiales have fixNOQP genes which encode cytochrome oxidase with high affinity to oxygen required for oxidative phosphorylation in microaerophilic conditions. There is one copy of the identified fixNOQP operon in ancestral forms of rhizobia (Bradyrhizobium), as well as in their putative evolutionary predecessors (bacteria related to Rhodopseudomonas). At the same time, forms deeply specialized in symbiosis (Rhizobium leguminosarum, Sinorhizobium meliloti) have multiple (2–3) copies, some of them have a high similarity (>90%) to fixNOQP genes of Bradyrhizobium and Rhodopseudomonas, and others have only 30–50% similarity. Two divergent copies fixNOQP are detected in Tardiphaga, which is a representative of the Bradyrhizobiaceae family, lacking the ability to fix N₂ (lack of nif genes encoding the synthesis of nitrogenase) and to induce the formation of nodules on legumes roots (lack of nod genes encoding the synthesis of signal Nod factors activating symbiosis development). The presence of Tardiphaga in nodule bacterial communities from a range of legumes, including Vavilovia formosa (relic representative of the tribe Fabeae, for which R. leguminosarum bv. viciae is the main microsymbiont), suggests that the ancestral gene duplication and subsequent divergence of fixNOQP operon in bacteria related to Tardiphaga opened the possibility of wide dissemination of functionally different copies of this cluster among symbiotically active forms of Rhizobiales. It is possible that the acquisition of fixNOQP genes determines adaptation of bacteria to microaerophilic niches not only in plants nodules but also in their environment (the rhizosphere, rhizoplane, internal portions of soil aggregates).

A study of the collection of sour cherry, sweet cherry, common plum, diploid and tetraploid types of plums, and apricots grown in Belarus carried out using 20 SSR markers showed that they are characterized by high genetic diversity. Among 106 genotypes, 524 polymorphic alleles were identified. The average number of alleles was 15.4 in common plum samples, 11.3 in diploid and tetraploid plum, 9.3 in sour cherry, 6.0 in apricot, and 4.9 in sweet cherry. The greatest genetic diversity is characteristic of common plum cultivars (PD = 0.811). The genetic diversity decreases as follows: diploid plum (PD = 0.741), sour cherry (PD = 0.721), apricot (PD = 0.673), and sweet cherry (PD = 0.655). Cluster analysis shows that the degree of intraspecific divergence in sour cherry and sweet cherry cultivars is less than that of common plum, diploid plum, and apricot plum. Although apricots and plums belong to the subgenus Prunophora, according to the results of SSR analysis, apricot cultivars form a cluster that is more distant from both Cerasus and Prunophora. A set of seven SSR markers (EMPA001, EMPA005, EMPA018, EMPA026 and BPPCT025, BPPCT026, BPPCT039) was selected for DNA identification of cultivars of sour cherry, sweet cherry, common plum, diploid plum, and apricot, as well as species and interspecies hybrids.

We conducted an association study of ten polymorphisms in six candidate genes of OA (rs1799750 (MMP1), rs35068180 (MMP3), rs2252070 (MMP13), rs63118460 and rs2276455 (COL2A1), rs143383 (GDF5), rs1544410, rs7975232, rs731236, and rs2228570 (VDR)) with the development of osteoarthritis (OA) in 333 women taking into account the localization of the pathological process, the age of disease manifestation, and ethnicity and investigated the presence of signs of undifferentiated connective tissue dysplasia (UCTD). On the basis of clinical and genetic data, we revealed statistically significant models to predict the development of osteoarthritis of various localizations (knee, hip, and generalized forms).

Breast cancer (BC) is one of the most common oncological diseases in the world and has a complex polygenic multifactorial character. The simultaneous analysis of a large number of medium- and low-penetrance genes in the genesis of the sporadic forms of BC makes it possible to more accurately predict the individual risk of this disease, and the analysis of their intergenic associations will help to identify the most significant interactions between several of them. This would significantly simplify further screening studies. In this study, we analyzed all possible combinations of pathogenetically significant polymorphic variants for the key genes involved in (1) repair systems (XRCC1, XRCC3, and PALB2); (2) biotransformation of xenobiotics (NAT2, EPHX1, GSTP1, GSTT1, and GSTM1); (3) cell cycle control (HMMR, TP53); and (4) folate cycle (MTHFR) among patients from Belarus (eastern European region) with the sporadic forms of BC and in the control group. The combinations of genotypes (genetic profile) significantly modifying the risk of sporadic BC were identified using the multifactor dimensionality reduction (MDR). The genetic profile (combinations of genotypes) leading to a significant increase in the risk of sporadic BC is the presence of the G allele in SNP p.I105V (GSTP1), the T allele in SNP p.T241M (XRCC3), and the AA genotype in SNP p.E429A (MTHFR).

According to the neonatal screening conducted during the last nine years in Karachay-Cherkessia, the frequency of hyperphenylalaninemia (including PKU) was 1: 850 newborns, which significantly exceeded the average frequency of 1: 7000 in Russia. Analysis of DNA obtained from 25 patients with a diagnosis of “hyperphenylalaninemia” (HPA) from the Karachay-Cherkess Republic was performed to search for mutations in the PAH gene. Mutations were identified on 90% of the studied chromosomes, while at least one mutation in the PAH gene was observed in all patients. The allele frequency of a major mutation R261X was 32.5%. A correlation between genotype and phenotype was confirmed in patients with HPA.

A model of a random mating diploid population with non-overlapping generations is considered. The dynamics of the population-genetic structure (with respect to a set of autosomal loci) under the pressure of recombination and segregation is investigated. In discrete time, the model is described by difference equations with respect to the population genetic state (the vector of multilocus gamete frequencies). Transition from the state description in terms of gamete frequencies to the description in terms of the fixed reference state with independent combining of alleles in gametes and deviations from such independence (gametic disequilibria) is made. According to the first part of the communication, it is possible to select among gametic disequilibria the basis ones, and the others are decomposed into the basis disequilibria. Basis gametic disequilibria have a hierarchical organization, which is determined by the number of loci starting from which it becomes possible to find the existing disequilibrium. From this point of view, we characterize the known results on the convergence of the multilocus genetic structure to an equilibrium state with independent combining of alleles in gametes. Basis gametic disequilibria of the first level of hierarchy decay the fastest. They are observed only at investigation of the whole given set of studied loci simultaneously and they cannot be discovered on the subsets of smaller sizes. Gametic disequilibria of the second level of hierarchy have slower rates of decay. These disequilibria are observed starting from the subsets of loci one unit less in size, but they are invisible at a smaller quantity of loci, etc. The description is based on the use of the coordinate system developed by S. Karlin and U. Liberman in analysis of non-epistatic selection models, but considered from another angle of view. Justification of the results assumes that readers are familiar with the basics of linear algebra and, in particular, the properties of Kronecker multiplication.

The migratory and stationary ecotypes of Atlantic cod are two ecological forms that differ by migratory behavior. Recent studies have revealed extended genomic regions associated with local adaptations of the ecotypes. In this study, a panel of markers was created to identify the variants of these genomic regions.