Deciphering Acclimation to Sublethal Combined and Sequential Abiotic Stresses in Arabidopsis thaliana

Abstract Plants are frequently exposed to environmental challenges. Responses to sublethal abiotic stress combinations are complex and often distinct from responses to individual stresses and remain poorly understood. Investigating traits and molecular factors mediating acclimation to stress combinations is essential for the development of climate change-resilient field crops. Here, we studied the morphological, physiological, and molecular responses of Arabidopsis thaliana to (i) co-occurring high temperature and drought and (ii) flooding followed by drought, both of which have increased in frequency due to climate change, and the individual component stresses: high temperature, drought, and flooding. A set of 15 physiological and morphological traits were assessed during single and combined stresses. By combining these comprehensive trait analyses with transcriptome characterization, we detected generally additive negative effects of simultaneous or sequential stresses on plant morphology and physiology compared with the corresponding individual stresses. Although drought had a mild effect on various growth, morphological, and physiological traits in both stress combinations, a unique transcriptome signature emerged upon combination with high temperature simultaneously, or flooding sequentially. Molecular processes identified as important for multistress resilience included plastid–nucleus communication, abscisic acid signaling, and photo-acclimation. Based on the RNA-seq data, a set of 39 genes were identified as potential multistress response regulators. Mutants were tested to validate the contribution of these genes to plant survival and phenotypic acclimation under combined stress. We confirmed the involvement of several genes. Among the identified factors were EARLY FLOWERING 6 (ELF6) and ARABIDOPSIS TÓXICOS EN LEVADURA 80 (ATL80), with substantial effects on plant growth, leaf development, and plant survival (wilting) during high-temperature drought and postsubmergence drought, respectively.