Rhizobial symbiosis promotes drought tolerance in Vicia sativa and Pisum sativum

Drought is one of the greatest threats to agricultural production. Legumes are relatively susceptible to drought and have the unique ability to establish symbiosis with nitrogen-fixing bacteria. Deciphering how symbiotic interactions affect legume stress tolerance is a relevant question that remains unsolved, especially in the context of maintaining crop production under climate change. Our study addresses the comparative analysis of drought response and drought tolerance in symbiosis-dependent versus N-fed plants. Our results support the existence of attenuation in the damage promoted by drought in nodulated pea and vetch plants. This increase in drought tolerance correlates with changes in physiological parameters, such the hydric status of the plant, changes in biochemical parameters, such as the accumulation of osmolytes and antioxidant pigments, or the protection against lipid peroxidation. We have also found changes at the molecular level, identifying different genomic pathways through transcriptomic analysis. Although this characterization strengthens the evidence for a com-mon strategy of coping with water deprivation in nodulated and N-fed plants, the above-mentioned changes suggest divergent and specific strategies of drought tolerance in nodulated plants as well as differences between pea and common vetch. In addition, our transcriptomic studies help unravel the molecular mechanisms through which rhizobial symbiosis contributes to drought tolerance in Vicia sativa and Pisum sativum. These results highlight the potential of using effective Rhizobium inoculants as a tool to cope with drought and enhance N -fixing ability under agriculturally relevant conditions.