Ectoine Reduces Nickel Stress and Boosts Antioxidant Defences in Wheat

Abstract

This study aimed to determine whether ectoine (ET), a bacterial compatible solute, can mitigate the adverse effects of nickel (Ni) toxicity in wheat plants. Treatments included 50 and 75 ppm Ni, with ET applied at 5 mM and 10 mM concentrations. Results showed that Ni stress significantly increased nickel accumulation in plant tissues (from 348 ppb in the control to 17.203 ppb under 50 ppm Ni), while reducing chlorophyll content from 1.38 to 1.01. However, application of 10 mM ET effectively ameliorated these effects by reducing nickel levels to 6.610 ppb (a 61.56% improvement) and increasing chlorophyll content from 1.01 to 1.22 (a 20.79% improvement). Nickel exposure also elevated oxidative stress markers, such as hydrogen peroxide and malondialdehyde (MDA), and increased the activities of antioxidant enzymes. Co-application of ET reduced these oxidative stress indicators and moderated enzyme activity, with 10 mM ET demonstrating the greatest protective effect. In the docking studies of ET with antioxidant enzymes, it was observed that ET exhibits a binding affinity ranging from - 6.3 to -4.6 kcal/mol. It was determined that a significant portion of ET interactions with antioxidant enzymes occurred with glutamine and lysine residues of these enzymes. These findings suggest that the role of ET as a compatible solute contributes to its ability to stabilize cellular structures, decrease reactive oxygen species (ROS) accumulation, and enhance antioxidant defences, indicating its potential as an effective agent for alleviating heavy metal stress in plants.