Integrative analysis of plant responses to a combination of water deficit, heat stress and eCO2

ABSTRACT The frequency, intensity, and duration of environmental stressors, such as droughts, heat waves, floods, and pollution, are increasing due to anthropogenic activities, subjecting plants to compound conditions of ‘multifactorial stress combination (MFSC)’. These can have contrasting or additive effects on plant physiological performance and impact different ecosystems and agro-ecosystems worldwide. Using an integrative physiological, genetic, hormonal, and transcriptomic analysis, we studied the response of Arabidopsis thaliana (L.) Heynh to a combination of water deficit (WD), heat stress (HS) and/or elevated levels of CO 2 (eCO 2 ). Our findings identified unique, as well as common, responses to MFSC. We further reveal that stomatal aperture regulation under conditions of MFSC is controlled by a combination of different pathways that is different than that activated in plants under less complex stress conditions. Under a combination of WD+HS+eCO 2 , for example, stomatal closure requires the function of the S-type anion channel SLAH3, but not the S-type anion channel SLAC1, or many other regulators typically found to control stomatal aperture under simpler conditions of abiotic stress/stress combinations. Our findings highlight the complexity of plant physiological and molecular responses to conditions of MFSC and open the way for future studies focused on how climate change and increased pollution impact different ecosystems and agro-ecosystems worldwide.