PLANT GENETICS AND BREEDING
Arbuscular mycorrhiza (AM) fungi receive photosynthetic products and sugars from plants in exchange for contributing to the uptake of minerals, especially phosphorus, from the soil. The identification of genes controlling AM symbiotic efficiency may have practical application in the creation of highly productive plant-microbe systems. The aim of our work was to evaluate the expression levels of SWEET sugar transporter genes, the only family in which sugar transporters specific to AM symbiosis can be detected. We have selected a unique “host plant–AM fungus” model system with high response to mycorrhization under medium phosphorus level. This includes a plant line which is highly responsive to inoculation by AM fungi, an ecologically obligate mycotrophic line MlS-1 from black medick (Medicago lupulina) and the AM fungus Rhizophagus irregularis strain RCAM00320, which has a high efficiency in a number of plant species. Using the selected model system, differences in the expression levels of 11 genes encoding SWEET transporters in the roots of the host plant were evaluated during the development of or in the absence of symbiosis of M. lupulina with R. irregularis at various stages of the host plant development in the presence of medium level of phosphorus available for plant nutrition in the substrate. At most stages of host plant development, mycorrhizal plants had higher expression levels of MlSWEET1b, MlSWEET3c, MlSWEET12 and MlSWEET13 compared to AM-less controls. Also, increased expression relative to control during mycorrhization was observed for MlSWEET11 at 2nd and 3rd leaf development stages, for MlSWEET15c at stemming (stooling) stage, for MlSWEET1a at 2nd leaf development, stemming and lateral branching stages. The MlSWEET1b gene can be confidently considered a good marker with specific expression for effective development of AM symbiosis between M. lupulina and R. irregularis in the presence of medium level of phosphorus available to plants in the substrate.
Modern varieties of common wheat (Triticum aestivum L.) bred mainly for high productivity are often of low grain quality. The identification of NAM-1 alleles associated with high grain protein content in wheat relatives has enhanced the significance of distant hybridization for the nutritional value of T. aestivum L. grain. In this work we aimed to study the allelic polymorphism of the NAM-A1 and NAM-B1 genes in wheat introgression lines and their parental forms and evaluate the effects of various NAM-1 variants on the grain protein content and productivity traits in the field conditions of Belarus. We studied parental varieties of spring common wheat, the accessions of tetraploid and hexaploid species of the genus Triticum and 22 introgression lines obtained using them (2017–2021 vegetation periods). Full-length NAM-A1 nucleotide sequences of T. dicoccoides k-5199, T. dicoccum k-45926, T. kiharae, and T. spelta k-1731 accessions were established and registered with the international molecular database GenBank. Six combinations of NAM-A1/B1 alleles were identified in the accessions studied and their frequency of occurrence varied from 40 to 3 %. The cumulative contribution of NAM-A1 and NAM-B1 genes to the variability of economically important wheat traits ranged from 8–10 % (grain weight per plant and thousand kernel weight) to up to 72 % (grain protein content). For most of the traits studied, the proportion of variability determined by weather conditions was small (1.57–18.48 %). It was shown that, regardless of weather conditions, the presence of a functional NAM-B1 allele ensures a high level of grain protein content; at the same time, it does not significantly decrease thousand kernel weight. The genotypes combining the NAM-A1d haplotype and a functional NAM-B1 allele demonstrated high levels of productivity and grain protein content. The results obtained demonstrate the effective introgression of a functional NAM-В1 allele of related species increasing the nutritional value of common wheat.
This review considers the processes of morphogenesis used in the development of propagation methods and the creation of a new starting material for sugar beet. It has been demonstrated that methods of particulation, in vitro microcloning and cell breeding that reflect non-sexual forms of plant reproduction increase the effectiveness of breeding experiments. The review describes the in vitro culture methods maintaing a tendency in plants for vegetative propagation and stimulating increase in genetic variability of properties when mutagens such as ethyl methanesulfonate, alien genetic structures with mf2 and mf3 bacterial genes in Agrobacterium tumefaciens strains, and selective agents (Сd++ ions and abscisic acid) are incorporated into plant cells. It presents the results of using fluorescent microscopy, cytophotometry, biochemical analysis and determining the level of phytohormones and content of nucleic acids in nuclei for forecasting the seed setting ability. It has demonstrated that long self-pollination of plants causes decrease in fertility of pollen grains, resulting in the sterilization of male gametes and the appearance of pistillody flowers. Self-fertile plants isolated from these lines serve as sterility fixers, while the apomixis elements increased the ovule number, additional embryo sacs and embryos. A role of apomixis in contributing to variability in the ontoand phylogenetic development of plants have been substantiated. The review reflects the morphological features of the in vitro development of sexual and somatic cells in embryos during the formation of seedlings based on floral and vegetative embryoidogeny. Use of the SNP and SSR (Unigenes) molecular-genetic markers having a high polymorphism level has appeared effective to characterize the developed breeding material and hybrid components when carrying out crossings. The study of sugar beet starting materials for the presence of TRs mini-satellite loci making it possible to reveal O-type plants-pollinators (sterility fixing agent) and MS-form plants are of interest for breeding as well. The selected material can be widely used in breeding to produce hybrids, allowing for a 2–3-fold reduction of the development period. The review also discusses the prospects for the development and implementation of new methods and original schemes in sugar beet genetics, biotechnology and breeding.
HUMAN GENETICS
Studies of the nature of mitochondrial DNA (mtDNA) variability in human populations have shown that proteincoding genes are under negative (purifying) selection, since their mutation spectra are characterized by a pro nounced predominance of synonymous substitutions over nonsynonymous ones (Ka/Ks < 1). Meanwhile, a number of studies have shown that the adaptation of populations to various environmental conditions may be accompanied by a relaxation of negative selection in some mtDNA genes. For example, it was previously found that in Arctic populations, negative selection is relaxed in the mitochondrial ATP6 gene, which encodes one of the subunits of ATP synthase. In this work, we performed a Ka/Ks analysis of mitochondrial genes in large samples of three regional population groups in Eurasia: Siberia (N = 803), Western Asia/Transcaucasia (N = 753), and Eastern Europe (N = 707). The main goal of this work is to search for traces of adaptive evolution in the mtDNA genes of aboriginal peoples of Siberia represented by populations of the north (Koryaks, Evens) and the south of Siberia and the adjacent territory of Northeast China (Buryats, Barghuts, Khamnigans). Using standard Ka/Ks analysis, it was found that all mtDNA genes in all studied regional population groups are subject to negative selection. The highest Ka/Ks values in different regional samples were found in almost the same set of genes encoding subunits of ATP synthase (ATP6, ATP8), NADH dehydrogenase complex (ND1, ND2, ND3), and cytochrome bc1 complex (CYB). The highest Ka/Ks value, indicating a relaxation of negative selection, was found in the ATP6 gene in the Siberian group. The results of the analysis performed using the FUBAR method (HyPhy software package) and aimed at searching for mtDNA codons under the influence of selection also showed the predominance of negative selection over positive selection in all population groups. In Siberian populations, nucleotide sites that are under positive selection and associated with mtDNA haplogroups were registered not in the north (which is expected under the assumption of adaptive evolution of mtDNA), but in the south of Siberia.
Glycosylation is an important protein modification, which influences the physical and chemical properties as well as biological function of these proteins. Large-scale population studies have shown that the levels of various plasma protein N-glycans are associated with many multifactorial human diseases. Observed associations between protein glycosylation levels and human diseases have led to the conclusion that N-glycans can be considered a potential source of biomarkers and therapeutic targets. Although biochemical pathways of glycosylation are well studied, the understanding of the mechanisms underlying general and tissue-specific regulation of these biochemical reactions in vivo is limited. This complicates both the interpretation of the observed associations between protein glycosylation levels and human diseases, and the development of glycan-based biomarkers and therapeutics. By the beginning of the 2010s, high-throughput methods of N-glycome profiling had become available, allowing research into the genetic control of N-glycosylation using quantitative genetics methods, including genome-wide association studies (GWAS). Application of these methods has made it possible to find previously unknown regulators of N-glycosylation and expanded the understanding of the role of N-glycans in the control of multifactorial diseases and human complex traits. The present review considers the current knowledge of the genetic control of variability in the levels of N-glycosylation of plasma proteins in human populations. It briefly describes the most popular physical-chemical methods of N-glycome profiling and the databases that contain genes involved in the biosynthesis of N-glycans. It also reviews the results of studies of environmental and genetic factors contributing to the variability of N-glycans as well as the mapping results of the genomic loci of N-glycans by GWAS. The results of functional in vitro and in silico studies are described. The review summarizes the current progress in human glycogenomics and suggests possible directions for further research.
INSECT GENETICS
Spider mites (Acari: Tetranychidae) are dangerous pests of agricultural and ornamental crops, the most economically significant of them belonging to the genera Tetranychus, Eutetranychus, Oligonychus and Panonychus. The expansion of the distribution areas, the increased harmfulness and dangerous status of certain species in the family Tetranychidae and their invasion of new regions pose a serious threat to the phytosanitary status of agroand biocenoses. Various approaches to acarofauna species diagnosis determine a rather diverse range of currently existing methods generally described in this review. Identification of spider mites by morphological traits, which is currently considered the main method, is complicated due to the complexity of preparing biomaterials for diagnosis and a limited number of diagnostic signs. In this regard, biochemical and molecular genetic methods such as allozyme analysis, DNA barcoding, restriction fragment length polymorphism (PCR-RFLP), selection of species-specific primers and real-time PCR are becoming important. In the review, close attention is paid to the successful use of these methods for species discrimination in the mites of the subfamily Tetranychinae. For some species, e. g., the two-spotted spider mite (Tetranychus urticae), a range of identification methods has been developed – from allozyme analysis to loop isothermal amplification (LAMP), while for many other species a much smaller variety of approaches is available. The greatest accuracy in the identification of spider mites can be achieved using a combination of several methods, e. g., examination of morphological features and one of the molecular approaches (DNA barcoding, PCR-RFLP, etc.). This review may be useful to specialists who are in search of an effective system for spider mite species identification as well as when developing new test systems relevant to specific plant crops or a specific region.
The signal pathway of actin remodeling, including LIM-kinase 1 (LIMK1) and its substrate cofilin, regulates multiple processes in neurons of vertebrates and invertebrates. Drosophila melanogaster is widely used as a model object for studying mechanisms of memory formation, storage, retrieval and forgetting. Previously, active forgetting in Drosophila was investigated in the standard Pavlovian olfactory conditioning paradigm. The role of specific dopaminergic neurons (DAN) and components of the actin remodeling pathway in different forms of forgetting was shown. In our research, we investigated the role of LIMK1 in Drosophila memory and forgetting in the conditioned courtship suppression paradigm (CCSP). In the Drosophila brain, LIMK1 and p-cofilin levels appeared to be low in specific neuropil structures, including the mushroom body (MB) lobes and the central complex. At the same time, LIMK1 was observed in cell bodies, such as DAN clusters regulating memory formation in CCSP. We applied GAL4 × UAS binary system to induce limk1 RNA interference in different types of neurons. The hybrid strain with limk1 interference in MB lobes and glia showed an increase in 3-h short-term memory (STM), without significant effects on long-term memory. limk1 interference in cholinergic neurons (CHN) impaired STM, while its interference in DAN and serotoninergic neurons (SRN) also dramatically impaired the flies’ learning ability. By contrast, limk1 interference in fruitless neurons (FRN) resulted in increased 15–60 min STM, indicating a possible LIMK1 role in active forgetting. Males with limk1 interference in CHN and FRN also showed the opposite trends of courtship song parameters changes. Thus, LIMK1 effects on the Drosophila male memory and courtship song appeared to depend on the neuronal type or brain structure.
MICROBIAL GENETICS
The picobirnaviruses (Picobirnaviridae, Picobirnavirus, PBVs) are currently thought to be animal viruses, as they are usually found in animal stool samples. However, no animal model or cell culture for their propagation has yet been found. In 2018, a hypothetical assumption about PBVs belonging to prokaryotic viruses was put forward and experimentally substantiated. This hypothesis is based on the presence of Shine–Dalgarno sequences in the genome of all PBVs before three reading frames (ORF) at the ribosomal binding site, with which the prokaryotic genome is saturated, while in the eukaryotic genome such regions occur with low frequency. The genome saturation with the Shine–Dalgarno sequences, as well as the preservation of this saturation in the progeny, according to scientists, allows us to attribute PBVs to prokaryotic viruses. On the other hand, there is a possibility that PBVs belong to viruses of eukaryotic hosts – fungi or invertebrates, since PBVlike sequences similar to the genome of fungal viruses from the families of mitoviruses and partitiviruses have been identified. In this regard, the idea arose that, in terms of reproduction mode, PBVs resemble fungal viruses. The divergence of views on the true PBV host(s) has sparked discussions among scientists and required further research to elucidate their nature. The review highlights the results of the search for a PBV host. The reasons for the occurrence of atypical sequences among the PBV genome sequences that use an alter native mitochondrial code of lower eukaryotes (fungi and invertebrates) for the translation of viral RNAdependent RNA polymerase (RdRp) instead of the standard genetic code are analyzed. The purpose of the review was to collect arguments in support of the hypothesis about the phage nature of PBVs and to find the most realistic explanation of the reasons for identifying nonstandard genomic sequences for PBVs. Based on the hypothesis about the genealogical relationship of PBVs with RNA viruses from other families with similar segmented genomes, such as Reoviridae, Cystoviridae, Totiviridae and Partitiviridae, virologists support the assumption of a decisive role in the origin of atypical PBVlike reassortment strains between PBVs and viruses of the listed families. The collected arguments given in this review indicate a high probability of a phage nature of PBVs. The data presented in the review show that the belonging of PBVlike progeny to prokaryotic or eukaryotic viruses is determined not only by its genome saturation level with a prokaryotic motif, standard or mitochondrial genetic code. The primary structure of the gene encoding the viral capsid protein responsible for the presence or absence of specific proteolytic properties of the virus that determine its ability for independent horizontal transmission into new cells may also be a decisive factor.
Bacterial species of the genus Rhodococcus are known to be efficient degraders of hydrocarbons in contaminated soil. They are also employed for bioremediation of polluted environments. These bacteria are widely met in soil, water and living organisms. Previously, we have isolated the Rhodococcus qingshengii strain VKM Ac-2784D from the rhizosphere of couch grass growing on oil-contaminated soil. This strain can effectively degrade oil and some model compounds (naphthalene, anthracene and phenanthrene). The results of phylogenetic analysis show that this strain belongs to the species R. qingshengii. To understand the catabolic properties of this strain, we have studied its gene clusters possessing such properties. The alkane destruction genes are represented by two clusters and five separate alkB genes. The destruction of aromatic compounds involves two stages, namely central and peripheral. The R. qing shengii VKM Ac-2784D genome contains four out of eight known central metabolic pathways for the destruction of aromatic compounds. The structure of the gene clusters is similar to that of the known strains R. jostii RHA1 and R. ru ber Chol-4. The peripheral pathways include the genes encoding proteins for benzoic acid destruction. The presence of biphenyl 2,3-dioxygeneses as well as gene clusters of benzoate and 2-hydroxypentandienoate pathways suggests that R. qingshengii VKM Ac-2784D could degrade polychlorinated biphenyls. The biodegradation ability can be enhanced by biosurfactants, which are known to be synthesized by Rhodococcus. The R. qingshengii VKM Ac-2784D genome contains the otsA, otsB, treY, treZ genes. The bioinformatics data are supported by the previous biochemical experiments that allow a mixture of species with a wide variation of metabolic pathways to be obtained.
BIOINFORMATICS
Telomeres are the terminal regions of chromosomes that ensure their stability while cell division. Telomere shortening initiates cellular senescence, which can lead to degeneration and atrophy of tissues, so the process is associated with a reduction in life expectancy and predisposition to a number of diseases. An accelerated rate of telomere attrition can serve as a predictor of life expectancy and health status of an individual. Telomere length is a complex phenotypic trait that is determined by many factors, including the genetic ones. Numerous studies (including genome-wide association studies, GWAS) indicate the polygenic nature of telomere length control. The objective of the present study was to characterize the genetic basis of the telomere length regulation using the GWAS data obtained during the studies of various human and other animal populations. To do so, a compilation of the genes associated with telomere length in GWAS experiments was collected, which included information on 270 human genes, as well as 23, 22, and 9 genes identified in the cattle, sparrow, and nematode, respectively. Among them were two orthologous genes encoding a shelterin protein (POT1 in humans and pot-2 in C. elegans). Functional analysis has shown that telomere length can be influenced by genetic variants in the genes encoding: (1) structural components of telomerase; (2) the protein components of telomeric regions (shelterin and CST complexes); (3) the proteins involved in telomerase biogenesis and regulating its activity; (4) the proteins that regulate the functional activity of the shelterin components; (5) the proteins involved in telomere replication and/or capping; (6) the proteins involved in the alternative telomere lengthening; (7) the proteins that respond to DNA damage and are responsible for DNA repair; (8) RNA-exosome components. The human genes identified by several research groups in populations of different ethnic origins are the genes encoding telomerase components such as TERC and TERT as well as STN1 encoding the CST complex component. Apparently, the polymorphic loci affecting the functions of these genes may be the most reliable susceptibility markers for telomere-related diseases. The systematized data about the genes and their functions can serve as a basis for the development of prognostic criteria for telomere length-associated diseases in humans. Information about the genes and processes that control telomere length can be used for marker-assisted and genomic selection in the farm animals, aimed at increasing the duration of their productive lifetime.