Regulation of Legume-Rhizobial Symbiosis: Molecular Genetic Aspects and Participation of Reactive Oxygen Species

Abstract

The formation of legume-rhizobial symbiosis goes through a series of coordinated stages, the main of which is the distant interaction of symbionts, which is carried out through the exchange of molecular signals between macro- and microsymbionts. There is clear regulation in the interaction between symbiosis partners: rhizobia with their associated molecular patterns (MAMPs) and the plant, which forms two types of immune response (MTI/ETI) to infection, leading to the activation of symbiotic processes in host plants and suppression of their functional systems. The development of protective reactions of legume plants to the invasion of rhizobia is very similar to the processes of pathogenesis. However, the result of symbiotic interaction is not the inactivation of the microorganism but rather the regulation of its reproduction and metabolic activity, primarily regulated by macrosymbionts. Clear regulation of precontact intermolecular events between both partners of symbiosis leads to the activation of the main pathways of symbiotic signals’ transduction and the successful development of organogenesis programs of the nodule–epidermal and cortical. The important participation of the reactive oxygen species in the regulation of symbiotic processes that occur on the early stages of interaction of macro- and microsymbionts (preinfection, infection, formation of infectious threads), as well as the prospects for further studies of these signaling molecules in integration with other transduction pathways of legume-rhizobial symbiosis formation, were highlighted. The review summarizes the current scientific information on the main molecular genetic mechanisms that underlie the regulation of symbiotic interaction of legumes with nodule bacteria as well as the participation of reactive oxygen species in the formation of legume-rhizobial symbiosis.

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