Effective symbiosis and activation of protective antioxidant systems for increasing soybean tolerance to drought

Abstract

Abstract Background and Aims In the face of increasing drought associated with a warming climate, encouraging rhizobial symbioses represents a promising Nature-Based Solution for providing legume crops with ecological nitrogen and increasing drought resistance. In addition, to effectively resist drought, plants must adapt under stress and activate key systems for antioxidant protection. The aim of the present study is to explore the role of protective antioxidant systems in the drought resistance of soybean, depending on the effectiveness of forming a symbiotic interaction with the nodula bacteria Bradyrhizobium japonicum. Methods The study uses microbiological, biochemical, physiological approaches and employs various symbiotic soybean systems based on Bradyrhizobiumstrains and Tn5 mutants, differing in activity and virulence. Results The effective symbiotic systems are able to activate the key antioxidant enzymes superoxide dismutase and catalase under prolonged drought, thus maintaining the prooxidant-antioxidant balance of plants and the functioning of the symbiotic relationship under stress conditions. The less effective and ineffective symbiotic systems are unable to provide the soybean plants with antioxidant protection due to the significant development of drought-related oxidative processes, as evidenced by excessive production of hydrogen peroxide and intensification of lipid peroxidation. Conclusion The formation of a tolerant soybean-rhizobial symbiosis is the result of the combined ability of both partners, i.e. the macro- and microsymbiont, to realize their adaptive potential and regulate redox homeostasis under effects of drought. This is achieved by activating key antioxidant enzyme systems, thus maintaining the prooxidant-antioxidant status of the symbiotic system.