Dynamics of Metabolic Responses to Combined Heat and Drought Spells in Arabidopsis Thaliana under Ambient and Rising Atmospheric CO2.

As a consequence of global change processes, plants will be increasingly challenged by extreme climatic events, against a background of elevated atmospheric CO2. We analysed responses of Arabidopsis thaliana to a combination of heat wave and water deficit at ambient and elevated CO2, and provided mechanistic insight on changes in primary metabolism. Climate extreme-induced metabolic changes are dynamic and molecule class-specific. Concentrations of soluble sugars and amino acids increased transiently after short (4 d) exposure to heat and drought, and readjusted to control levels under prolonged (8 d) stress. In contrast, fatty acids showed persistent changes during the stress period. Elevated CO2 reduced the stress impact on sugar and amino acid metabolism, but not on fatty acids. Integrating metabolite data with transcriptome results, revealed that some of the metabolic changes are regulated at the transcriptional level. Multivariate analyses grouped metabolites on the basis of stress exposure time, indicating specificity in metabolic responses to short and prolonged stress. Taken together, the results indicate that dynamic metabolic reprograming plays an important role in plant acclimation to climatic extremes. The extent of such metabolic adjustments is less under high CO2, further pointing towards the role of high CO2 in stress mitigation.