Individual vs. Combinatorial Effect of Elevated CO2 Condition and Drought Stress on Physiological and Molecular Response of Glycine max Roots

Climate changes increasingly threaten plant growth and productivity. Soybean (Glycine max) is one of the most important crops in the world and although responses of soybean to increase in atmospheric [CO₂] have been previously studied, there is no report of root molecular responses of this plant under elevated [CO₂] (E[CO₂])  nor the combination of E[CO₂] and drought. In this study, we evaluated the individual and combinatory effect of E[CO₂] and drought on physiology and root molecular responses in soybean. Plants were grown hydroponically in open-top chambers under ambient and E[CO₂] and drought stress was applied followed by RNA-seq analyses. Plants growing under E[CO₂] had photosynthesis increased which result in higher biomass, plant height and leaf area. E[CO₂] decreases transcripts levels of genes related to iron uptake and transport, antioxidant activity, secondary metabolism and defense and stress responses in roots. Both physiological and transcriptomic analysis data showed that E[CO₂] may mitigate in some extend the negative effects of drought. However, the identification of genes that are modulated by the interaction effect CO₂:drought may draw attention to unexpected consequences to soybean yields. Our data provide a distinctive overview of the molecular responses of soybean roots to the global climate changes.