Search

In order to investigate the effect of the RapA1 protein on growth-stimulating activity, biofilm formation, and root colonization by rhizobia, strains Rhizobium leguminosarum Pvu5, VSy12, Thy2, TPr4 and R. galegae 0702 were transformed with the pJN105TurboRapA1GFP vector, providing for constitutive expression of the rapA1 and gfp genes. Constitutive expression of the rapA1 gene was shown to result in more efficient biofilm formation on inert surfaces and to promote microcolony formation on plant root surfaces. Analysis of auxin production by wild and transformed strains revealed decreased auxin synthesis in all transformed strains, except for R. leguminosarum Thy2. Growth-stimulating activity of the wild and transformed strains did not correlate with the amount of auxins produced in vitro.

The genetic diversity and phylogeny of root module bacteria entering into symbiotic relations with Caragana arborescens introduced on the territory of the Republic of Bashkortostan (RB) were studied. Analysis of the 85 strains isolated from root-nodules showed that, according to the DNA polymorphism revealed by RAPD analysis, they can be divided into 12 groups. It was found that, both in natural habitats and on the territory of the RB, Caragana arborescens is primarily nodulated by Mesorhizobium bacteria whose 16S rRNA gene sequences differ to some degree from those of the bacteria described earlier by Chinese authors. Bacteria assigned to the genus Phyllobacterium based on their 16S rRNA gene sequences were also revealed in plants growing on the territory of the RB.

Biomethods in plant protection against pests and diseases considered the most prospective alternative to chemicals which pollute soil and water causing concern about public health. The possibility of creating an artificial association of nodule bacteria with plants to protect them from the adverse effects of pathogenic fungi can be realized using one of the specific mechanism of nodule bacteria attachment to the roots of leguminous plants by plant lectins, able to recognize and specifically bind with different carbohydrates, particularly polysaccharides of rhizobia cell wall. In our study we used the composite plants of tomato (Lycopersicon esculentum) Dubok variety and bacterial strains associated with the roots of wild legumes from the collection of Institute of Biochemistry and Genetics (IBG USC RAS). «Hairy rooted» tomato plants were obtained by treatment with Agrobacterium rhizogenes ATCC 15834, containing vehicle gene construction pCambia 1305.1 with inserted pea lectin gene psl under cauliflower mosaic virus 35S promoter. The antagonistic activity of bacteria towards pathogens was tested by dual culture study. The ability of microorganisms to produce siderophores and cyanide was analyzed. Few isolates were identified by sequencing of the 16S rRNA gene fragments. By screening of the collection of isolates from nodules of wild legume from tribe Viceae the candidate strains were detected, particularly Rhizobium leguminosarum, Pseudomonas sp. and Stenotrophomonas rhizophila, with fungistatic activity against Fusarium solani, F. oxysporum, Fusarium sp. and F. oxysporum f. sp. lycopersici. Prodiction of siderophores was detected in two members of Pseudomonas genus, S. rhizophila and R. leguminosarum. Two Pseudomonas strains, the 14M and 103, and S. rhizophila were shown to produce cyanide. It was also found that treatment of roots transgenic by psl gene with R. leguminosarum 116 strain reduced the amount of hyphae of the pathogen F. oxysporum f. sp. lycopersici in the rhizosphere of tomato plant that could potentially contribute to plant defense against pathogenic fungi. Thus, the use of lectins as transgenes in roots allows us to obtain artificial association with rhizobia in non-symbiotic plants such as tomato, which in combination with the use of microorganisms possessing fungistatic activity can more effectively protect the plant root system o against pathogens.

The genetic diversity and phylogeny of rhizobia from eight genera belonging to four tribes (Loteae, Genisteae, Galegeae, and Hedysareae) that nodulate 18 species of South Urals wild-growing bean plants are studied. It is demonstrated that symbiotic interaction with various strains of nodule bacteria that are closely related to bacteria of Mesorhizobium sp. was typical for the wild growing plants of the Galegeae and Hedysareae tribes and interaction with bacteria of Bradyrhizobium sp. for the plants of the Genisteae tribe. A rhizobium that is closely related to the bacteria of Mesorhizobium sp. is found in the nodules of Lotus ucrainicus from the Loteae tribe, and Coronilla varia rhizobia strains obtained are found to be closely related to Rhizobium sp., based on the sequence of a 16S rRNA gene. Some minor species of rhizobia, the structure of which is greatly influenced by the conditions of the host plant growth, were also found in the nodules of some kinds of investigated plants.

Sea-buckthorn (Hyppopha L.) transgenic roots transformed with the lectin gene were obtained using the wild-type strain of Agrobacterium rhizogenes 15834 preliminary transformed with the plasmid pCAMBIA 1305.1, which contained the full-size pea lectin gene. Effects of lectin gene expression on symbiotic responses of sea-buckthorn to inoculation with rhizobia (Rhizobium leguminosarum, pea symbiont) and actinomycetes of genus Frankia (sea-buckthorn symbiont) were studied. In sea-buckthorn seedlings, whose transgenic roots were inoculated with both microsymbionts simultaneously, atypical nodule-like structures were found along with typical actinorhizal nodules. Random amplified polymorphic DNA (RAPD) analysis of bacteria, isolated from these structures, revealed the presence of R. leguminosarum rhizobia and the absence of Frankia actinomycetes.