Soybean drought resilience: contributions of a brassinosteroid functional analogue.

Drought is one of the most important causes of severe yield loss in soybean worldwide, threatening food production for the coming years. Phytohormones such as brassinosteroids can increase response to water deficit. However, natural brassinosteroids low stability precludes large-scale field application, challenging research and development of more stable and cost-effective analogues. Seeking functional analogues capable of improving plant drought-response, we investigated for the first time the effect of DI-31 in Arabidopsis and soybean. We found that, in A. thaliana, the DI-31 increased root growth, biomass accumulation, leaf number per plant, triggered antioxidant response and dose-dependent stomatal closure, requiring NADPH and peroxidase-dependent ROS production. In soybean, the relative water content, water use efficiency, biomass production and duration, root length, free proline, chlorophyll and carotenoid accumulation and enzymatic antioxidants activity were stimulated by DI-31 application after four and eight days of mild water shortage, while significantly reduced the lipid-peroxides content. Additionally, our results demonstrated that DI-31 diminishes the nodular senescence and successfully maintains the N homeostasis through a fine tune of biological/assimilative N2-fixation pathways. These findings support the DI-31 potential use as a sustainable alternative for integrative soybean resilience management under drought.nnHighlightBrassinosteroid analogue DI-31 improves soybean growth, water economy, respiration, anti-stress response and nitrogen homeostasis under drought. Thus, they may be considered as a sustainable and environmentally-safe alternative for raising legumes climate resilience.