S u m m a r yIn the studies of Melilotus dentatus Pers. populations from different geographically remote areas (North Caucasus and Kazakhstan), a compex approach of intra-and inter-population analysis of taxonomically important molecular markers (ITS) was used. The analysis of receptor gene nfr5 was also made. It is shown that the Melilotus dentatus Pers. plants differ at both intra-and inter-population levels. A consolidation of sweet clover's populations to clusters is observed according to their geographic location. An independent distribution of populations on receptor part of nfr5 gene concerning cluster structure of ITS region is determined.Keywords: Melilotus dentatus Pers., genetic diversity, nfr5 gene.In global agriculture, sweet clover is a fodder plant less important than other leguminous forage grasses. At the same time, detailed recent studies show a number of valuable economical properties of Melilotus dentatus Pers.: high drought resistance, winter hardiness, along with better immunity against pests and diseases compared with other legumes (1), and better consumption by animals due to lower content of coumarin (2). Its ability to grow on saline lands allows using sweet clover in soil recultivation through the creation of saline-resistant legume-rhizobial complex. Such programs require the plants with improved symbiotic efficiency, which is largely determined by the genotype.The peculiarity of legume-rhizobium symbiosis is a signal exchange between both partners whose signaling molecules trigger the mechanism of formation of a specialized new organ -nodule. In response to the specific inducers -flavonoids released in soil by a host plant, nitrogen-fixing bacteria start the production of signaling molecules (Nod-factors) that initiate the formation of root nodules in leguminous plants (3). All Nod-factors are lypochytho-oligosaccharides. Legume plants have seven genes presumably involved in signaling recognition and interaction with symbiotic rhizobia (4). The family of LYK genes is of particular interest, which include nfr1 and nfr5 first identified in Lotus japonicus (3, 5), Sym10 and Sym2 in Pisum sativum (3), as well as NFP gene in diploid alfalfa (6, 7). These genes encode LysM-containing receptor kinase, and they have domain structure typical for plants: extracellular LysM-domains -probable participants in the reception of Nod-factor, a transmembrane domain, and an intracellular domain of serine / threonine kinase.The genes containing LysM-encoding regions (LysM-motifs) belong to an ancient and quite diverse group widespread in all kingdoms except Archaea (7). Phylogenetic analysis has shown that some sequences of bacterial LysM-motifs have common roots with nucleotide sequences of fungi, plants, insects and animals. This allowed suggesting that one group of these genes had been formed before the divergence of plants and animals, while the other group is the result of convergent evolution. A structural resemblance of LysM-containing protein kinase and the peptidogycan component of bacterial ce...
Sinorhizobium meliloti are agriculturally valuable species of soil bacteria that form nitrogen-fixing symbiosis with alfalfa plants. Global climate changes lead to an increase of agricultural areas subjected to salinity. Current knowledge about about high-salt stress impact on soil saprophitic root nodulated microsymbionts of legumes is weakly studied and rhizobia gene pool responsible for salt tolerance are fragment and far from clear. An increase of bacteria nonspecific resistance (immune status) to unfavorable stress factors can occur through the induction of defense mechanisms like restrictionmodification systems and CRISPR/cas systems which are aimed to protect bacteria cells from bacteriophages widespread in soil microbiome. The aim of this research was to evaluate the role of the megaplasmid pSymA in the formation of ecological genome of S. meliloti, which is related to stress tolerance and to determine the location of elements of adaptive immune systems protecting root nodule bacteria against external foreign DNA. The analysis was done on 11 genes, products of which involved in response to ion stress and synthesis of osmoprotectors. It was found that 6 out of 11 genes were found in the genomes of all analyzed S. meliloti strains, while it was not a case for other 5 genes. It was found that, unlike chromosome, megaplasmid I of S. meliloti accumulated copies of 4 from 5 genes, except kdpA gene, which is represented by a single copy and localized on megaplasmid I in all so far studied strains. It was predicted that closest phylogenetic relatives of genes whose products are involved in response to ion stress as well in synthesis of osmoprotectors are homologous genes of closely related S. medicae species. The exception was for betI2, for which the closest phylogenetic relative was homologous gene of Klebsiella pneumonia, and another exception is kdpA gene introduced onto megaplasmid-I from actinobacteria. Regarding elements of immune systems it was revealed that nonsymbiotic plasmids of S. meliloti harbored incomplete elements of RMS-I, -II, and - III systems, while the 4 complete RMS-IV systems were detected on a single plasmid. It was found out that corresponding methylases had similarities with similar enzymes detected in nitrogen-fixing strains of Agrobacterium tumefaciens, Mezorhizobium sp., Bradyrhizobium sp. CRISPR sequences were not detected on megaplasmid-I, while they were on chromosome, megaplasmid-II and on cryptic plasmids. So, it was concluded that megaplasmid-I of S. meliloti are enriched in copies of genes related to osmotic stress tolerance, but it role in immune status of rhizobia is requested further elucidation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.