Ecological and genetic bases for construction of highly effective nitrogen-fixing microbe-plant symbioses

Abstract

Expression of quantitative traits characterizing the N₂-fixing symbiosis of nodule bacteria and leguminous plants is associated with operation of the evolutionary derived polygenic systems controlling the symbiotic efficiency (SE) (impact of inoculation on the plant productivity) and nodulation competitiveness (NC) (formation of nodules by rhizobia under mixed inoculation). Optimization of balance between positive and negative symbiotic regulators aimed at an increase of nitrogenase activity and at a complete allocation of its products into the plant metabolism provides the generation of rhizobia strains with high SE and NC. Inactivation of the negative symbiotic regulators often results in a decreased survival of rhizobia under the edaphic stresses but is responsible for a balanced increase of plant biomass and N accumulation. Improvement of symbiotic activity is to be based on the complementary interactions of microorganisms with the genetically engineered plant cultivars which are able for selection from soil of actively fi xing N₂ rhizobia strains and for their preferential multiplication in nodules. Construction of highly effective microbe-plant systems should be based on modifications of mechanisms controlling symbiosis development from the plant and bacterial sides providing the maintenance of N₂-fixing zone in nodules and synthesis of NCR proteins activating the bacteroid differentiation.

Keywords

microbe-plant interactions / nodule bacteria (rhizobia) / leguminous plants / symbiotic nitrogen fixation / positive and negative regulators of symbiosis / signal interactions / systemic regulation of nodule development / evolution of symbiosis / genetic engineering

Funding

Russian Science FoundationРоссийский научный фонд()

RIGHTS & PERMISSIONS

Provorov N.A., Onishchuk O.P.