Short-term responses of soybean roots to individual and combinatorial effects of elevated [CO2] and water deficit

Abstract Climate change increasingly threatens plant growth and productivity. Soybean ( Glycine max ) is one of the most important crops in the world. Although its responses to increased atmospheric carbon dioxide concentration ([CO 2 ]) have been previously studied, root molecular responses to elevated [CO 2 ] (E[CO 2 ]) or the combination/interaction of E[CO 2 ] and water deficit remain unexamined. In this study, we evaluated the individual and combinatory effects of E[CO 2 ] and water deficit on the physiology and root molecular responses in soybean. Plants growing under E[CO 2 ] exhibited increased photosynthesis that resulted in a higher biomass, plant height, and leaf area. E[CO 2 ] decreased the transcripts levels of genes involved in iron uptake and transport, antioxidant activity, secondary metabolism and defense, and stress responses in roots. When plants grown under E[CO 2 ] are treated with instantaneous water deficit, E[CO 2 ] reverted the expression of water deficit-induced genes related to stress, defense, transport and nutrient deficiency. Furthermore, the interaction of both treatments uniquely affected the expression of genes. Both physiological and transcriptomic analyses demonstrated that E[CO 2 ] may mitigate the negative effects of water deficit on the soybean roots. In addition, the identification of genes that are modulated by the interaction of E[CO 2 ] and water deficit suggests an emergent response that is triggered only under this specific condition.