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Provorov N.A.,Saint Petersburg State University | Vorobyev N.I.,All Russia Research Institute for Agricultural Microbiology
Applied Biochemistry and Microbiology | Year: 2015

The literature and our own data on N2-fixing bacteria forming symbioses with plants and providing convenient models to study the evolution of interspecies (microsymbionts → hosts) altruism are considered in the review. It is presented as a deeply reorganized intraspecies altruism implemented in the clonal population of rhizobia (bacteroids → undifferentiated bacteria) under the control of kin selection induced by plant hosts. The analysis of this model suggests that it is possible to engineer practically valuable rhizobial strains in which high N2-fixing activity is combined with decreased survival outside of plants. © 2015, Pleiades Publishing, Inc.

Vorobyov N.I.,All Russia Research Institute for Agricultural Microbiology | Provorov N.A.,Saint Petersburg State University of Information Technologies, Mechanics and Optics
Russian Journal of Genetics: Applied Research | Year: 2015

A mathematical model is constructed which describes the impacts of a chaotically changing environment on the frequencies and productivity of partners in the legume-rhizobia symbiosis (LRS). The most sensitive for external impacts are the adaptively prospective bacteria strains which are specific with respect to hosts and are capable for the intensive evolution towards an improved symbiotic efficiency. The increased stability of these strains in the symbiotic system may be an important factor of its evolution for the improved efficiency of partners’ interaction. © 2015, Pleiades Publishing, Ltd.

Chen L.,Lancaster University | Dodd I.C.,Lancaster University | Theobald J.C.,Lancaster University | Belimov A.A.,All Russia Research Institute for Agricultural Microbiology | Davies W.J.,Lancaster University
Journal of Experimental Botany | Year: 2013

Many plant-growth-promoting rhizobacteria (PGPR) associated with plant roots contain the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase and can metabolize ACC, the immediate precursor of the plant hormone ethylene, thereby decreasing plant ethylene production and increasing plant growth. However, relatively few studies have explicitly linked ethylene emission and/or action to growth promotion in these plant-microbe interactions. This study examined effects of the PGPR Variovorax paradoxus 5C-2 containing ACC deaminase on the growth and development of Arabidopsis thaliana using wild-type (WT) plants and several ethylene-related mutants (etr1-1, ein2-1, and eto1-1). Soil inoculation with V. paradoxus 5C-2 promoted growth (leaf area and shoot biomass) of WT plants and the ethylene-overproducing mutant eto1-1, and also enhanced floral initiation of WT plants by 2.5 days. However, these effects were not seen in ethylene-insensitive mutants (etr1-1 and ein2-1) even though bacterial colonization of the root system was similar. Furthermore, V. paradoxus 5C-2 decreased ACC concentrations of rosette leaves of WT plants by 59% and foliar ethylene emission of both WT plants and eto1-1 mutants by 42 and 37%, respectively. Taken together, these results demonstrate that a fully functional ethylene signal transduction pathway is required for V. paradoxus 5C-2 to stimulate leaf growth and flowering of A. thaliana. © 2013 The Authors.

Dodd I.C.,Lancaster University | Zinovkina N.Y.,All Russia Research Institute for Agricultural Microbiology | Safronova V.I.,All Russia Research Institute for Agricultural Microbiology | Belimov A.A.,All Russia Research Institute for Agricultural Microbiology
Annals of Applied Biology | Year: 2010

Plant growth-promoting rhizobacteria are commonly found in the rhizosphere (adjacent to the root surface) and may promote plant growth via several diverse mechanisms, including the production or degradation of the major groups of plant hormones that regulate plant growth and development. Although rhizobacterial production of plant hormones seems relatively widespread (as judged from physico-chemical measurements of hormones in bacterial culture media), evidence continues to accumulate, particularly from seedlings grown under gnotobiotic conditions, that rhizobacteria can modify plant hormone status. Since many rhizobacteria can impact on more than one hormone group, bacterial mutants in hormone production/degradation and plant mutants in hormone sensitivity have been useful to establish the importance of particular signalling pathways. Although plant roots exude many potential substrates for rhizobacterial growth, including plant hormones or their precursors, limited progress has been made in determining whether root hormone efflux can select for particular rhizobacterial traits. Rhizobacterial mediation of plant hormone status not only has local effects on root elongation and architecture, thus mediating water and nutrient capture, but can also affect plant root-to-shoot hormonal signalling that regulates leaf growth and gas exchange. Renewed emphasis on providing sufficient food for a growing world population, while minimising environmental impacts of agriculture because of overuse of fertilisers and irrigation water, will stimulate the commercialisation of rhizobacterial inoculants (including those that alter plant hormone status) to sustain crop growth and yield. Combining rhizobacterial traits (or species) that impact on plant hormone status thereby modifying root architecture (to capture existing soil resources) with traits that make additional resources available (e.g. nitrogen fixation, phosphate solubilisation) may enhance the sustainability of agriculture. © 2010 Association of Applied Biologists.

Provorov N.A.,All Russia Research Institute for Agricultural Microbiology | Vorobyov N.I.,All Russia Research Institute for Agricultural Microbiology
Theoretical Population Biology | Year: 2010

We created the mathematical model for the evolution of the Efficiency of Mutualistic Symbioses (EMS) which was estimated as the microsymbiont impacts on the host's reproductive potential. Using the example of rhizobia-legume interaction, the relationships were studied between EMS and Functional Integrity of Symbiosis (FIS) which is represented as a measure for concordance of changes in the partners' genotypic frequencies under the environmental fluctuations represented by the minor deviations of the systemic model parameters. The FIS indices correlate positively with EMS values suggesting an enhancement of FIS via the natural selection operating in the partners' populations in favor of high EMS. Due to this selection, nodular habitats may be closed for colonization by the non-beneficial bacterial strains and the Genotypic Specificity of Mutualism (GSM) in partners' interactions is enhanced: the selective advantage of host-specific vs non-host-specific mutualists is increasing. The novelty of our model is to suggest a selective background for macroevolutionary events reorganizing the structure and functions of symbiotic systems and to present its evolution as a result of shifting the equilibrium between different types of mutualists under the impacts of the symbiosis-stipulated modes of natural selection. © 2010 Elsevier Inc.

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