Metabolic adaptations in plants under the combination of salinity and high irradiance

Abstract

Climate change is shown as a combination of atmospheric phenomena and human-made pollution that have been aggravated over the last years. Among the different climate changeassociated environmental conditions, increased salinity in soils (S) combined with high light irradiances (HL) is one of the abiotic stress combinations that most affects global crop productivity. Plant responses to unfavorable conditions include physiological, metabolomic, and molecular changes that are tailored to the stress/stress combination impacting a plant. The present doctoral thesis is divided into three chapters. In Chapter 1, the metabolic response of two Arabidopsis ecotypes, Columbia-0 (Col) and Landsberg erecta (Ler) subjected to combined salinity and high light irradiance (S+HL) is compared. Our study reveals that both Col and Ler trigger a similar physiological response to S+HL. However, different metabolic profiles between both ecotypes subjected to S+HL are observed, including the accumulation of polyamides and flavonoids. In this work, it is suggested that Ler could exhibit an advantage in dealing with combined stress since they significantly accumulate both polyamides and flavonoids. In Chapter 2, using Arabidopsis mutants deficient in the accumulation of different phytohormones including ABA (aba2-11 and aba1-1), SA (sid2) and JA (aos), it is demonstrated that ABA is the key phytohormone for plant tolerance to S+HL. In this sense, ABA-deficient plants show a decreased survival rate with respect to their wild type or to sid2 and aos plants under stress combination conditions. Finally, in Chapter 3, we conclude that plants deficient in alpha-Tocopherol (alpha-Tc; Vitamin E; vte4-4 and Salk_036736C), a non-enzymatic antioxidant, plays a key role for plant tolerance to S+HL and could lead to the activation of other defense mechanism such as autophagy, APX2-mediated antioxidant responses, or an increased accumulation of ABA and SA under S+HL conditions. On the whole, this work provides novel information about physiological, metabolic and molecular responses to combined high salinity and high light irradiances. Our results suggest that ABA and alpha-Tc represent essential players in signaling plant acclimation to this combined stress situation.