Changes in physio-biochemical parameters and expression of metallothioneins in Avena sativa L. in response to drought

Drought is one of the major threats to food security. Among several mechanisms involved in plant stress tolerance, one protein family—the plant metallothioneins (MTs)—shows great promise for enhancing drought resistance. Plant metallothioneins in oat (Avena sativaL.) have not yet been deeply analysed, and the literature lacks a comprehensive study of the whole family of plant MTs in response to drought. In this study, we showed that the number and nature ofcis-elements linked with stress response in promoters ofAsMTs1–3differed depending on the MT type. Drought stress in oat plants caused an increase in the expression ofAsMT2andAsMT3and a decrease in the expression ofAsMT1compared to well-watered plants. Moreover, the low values of relative water content, water use efficiency, net photosynthesis (PN), transpiration (E), stomatal conductance (gs), chlorophylla, and carotenoid were accompanied by high levels of electrolyte leakage, internal CO2concentration (Ci) and abscisic acid content, and high activity of antioxidants enzymes in plants under drought stress. The present study puts forward the idea thatAsMTsare crucial for oat response to drought stress not only by regulating antioxidant activity but also by changing the plant water regime and photosynthesis. Our results support the hypothesis that structural differences among types of plant MTs reflect their diversified physiological roles.