Physiological, biochemical, and genome‐wide transcriptional analysis reveals that elevated CO₂ mitigates the impact of combined heat wave and drought stress in Arabidopsis thaliana at multiple organizational levels

Abstract

Climate changes increasingly threaten plant growth and productivity. Such changes are complex and involve multiple environmental factors, including rising CO2 levels and climate extreme events. As the molecular and physiological mechanisms underlying plant responses to realistic future climate extreme conditions are still poorly understood, a multiple organizational level analysis (i.e. eco-physiological, biochemical, and transcriptional) was performed, using Arabidopsis exposed to incremental heat wave and water deficit under ambient and elevated CO2 . The climate extreme resulted in biomass reduction, photosynthesis inhibition, and considerable increases in stress parameters. Photosynthesis was a major target as demonstrated at the physiological and transcriptional levels. In contrast, the climate extreme treatment induced a protective effect on oxidative membrane damage, most likely as a result of strongly increased lipophilic antioxidants and membrane-protecting enzymes. Elevated CO2 significantly mitigated the negative impact of a combined heat and drought, as apparent in biomass reduction, photosynthesis inhibition, chlorophyll fluorescence decline, H2 O2 production, and protein oxidation. Analysis of enzymatic and molecular antioxidants revealed that the stress-mitigating CO2 effect operates through up-regulation of antioxidant defense metabolism, as well as by reduced photorespiration resulting in lowered oxidative pressure. Therefore, exposure to future climate extreme episodes will negatively impact plant growth and production, but elevated CO2 is likely to mitigate this effect.

Physiological and molecular alterations in plants exposed to high [CO2] under phosphorus stress

“…oxidative pressure (Farfan-Vignolo and Asard, 2012;Naudts et al, 2014;Zinta et al, 2014 Phosphorous being a major constituent of nucleic acid (about 40-60% P in the cell), P deficiency affects RNA synthesis and protein synthesis, and thus inhibits metabolism including photosynthesis. Optimum photosynthesis requires 2.0-2.5 mM P is required in the chloroplast.…”

“…Many experiments have been carried out to study the responses of plants to high [CO 2 ] at various levels ranging from the ecosystem to the genome (e.g. Ainsworth and Long 2005;Luo et al, 2006;Teng et al, 2006;Niu et al, 2011;Dieleman et al, 2012;AbdElgawad et al, 2014;Zinta et al, 2014). Such studies revealed that elevated [CO 2 ] increases plant growth and crop yield by the stimulation of carboxylation and suppression of oxygenation activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) particularly in C3 plants, whereas the effects are marginal in C4 plants because Rubisco is already saturated at ambient [CO 2 ] (reviewed by Bowes 1991;Ghannoum et al, 2003;Feng et al, 2014).…”

NPR1-dependent salicylic acid signaling is not involved in elevated CO2-induced heat stress tolerance in Arabidopsis thaliana

“…However, for hsp21 mutants, other protective processes such as efficient reactive oxygen species (ROS) detoxification, improved redox homeostasis and decreased photorespiration as consequences of CO 2 enrichment might occur. 8 Together, this work indicates that NPR1-mediated SA signaling is important for basal thermotolerance; however, NPR1 is not required for elevated CO 2 -induced HS mitigation in Arabidopsis. Elevated CO 2 could ameliorate HS-induced deleterious effect on photosynthetic apparatus without involvement of HSP21, but basal thermotolerance as well as elevated CO 2 -induced HS tolerance largely depends on HSP70-1 in Arabidopsis.…”

“…7 Previous studies indicate that elevated CO 2 could minimize HS-induced deleterious effects on plants. 7,8 Nonetheless, the mechanisms of elevated CO 2 -induced HS mitigation are unknown. Previously, we have demonstrated that elevated CO 2 -induced HS mitigation does not involve abscisic acid-dependent process in tomato.…”

“…Elevated CO 2 might stimulate cellular redox homeostasis and MAPK activity and thus ameliorate HS through NPR1-independent process in npr1-1 and npr1-5 mutants. 7,8,10,11 HSPs protect various important proteins from irreversible heat-induced damage through preventing denaturation as well as assisting the refolding of damaged protein. 1,4,9 The inability of hsp21 and hsp70-1 to produce respective proteins aggravated HS-induced damage to photosynthetic apparatus (Fig.…”