Physiological and metabolomic responses of the ethylene insensitive squash mutant etr2b to drought
Jessica Iglesias‐Moya, Ana Cristina Abreu, Sonsoles Alonso, M. Trinidad Torres‐García, Cecilia Martínez, Ignacio Fernández, Manuel Jamilena
Abstract
The squash gain-of-function mutant etr2b disrupts the ethylene-binding domain of ethylene receptor CpETR2B, conferring partial ethylene insensitivity, changes in flower and fruit development, and enhanced salt tolerance. In this paper, we found that etr2b also confers a growth advantage as well as a physiological and metabolomic response that make the mutant better adapted to drought. Mutant plants had a higher root and leaf biomass than WT under both well-watered and drought conditions, but the reduction in growth parameters in response to drought was similar in WT and etr2b. Water deficit reduced all gas-exchange parameters in both WT and etr2b, but under moderate drought the mutant increased photosynthesis rate in comparison with control conditions, and showed a higher leaf CO2 concentration, transpiration rate, and stomata conductance than WT. The response of etr2b to drought indicates that ethylene is a negative regulator of plant growth under both control and drought. Since etr2b increased ABA content in well-watered plant, but prevented the induction of ABA production in response to drought, it is likely that the etr2b response under drought is not mediated by ABA. A 1H NMR metabolomic analysis revealed that etr2b enhances the accumulation of osmolytes (soluble sugars and trigonelline), unsaturated and polyunsaturated fatty acids, and phenolic compounds under drought, concomitantly with a reduction of malic- and fumaric-acid. The role of CpETR2B and ethylene in the regulation of these drought-protective metabolites is discussed.