The Role of L-histidine on Nickel Translocation and Antioxidant enzymes activity in Hyperaccumulator (Odontarrhena inflata) and Non-accumulator (Aurinia saxatilis) plants

Abstract

Abstract Background and Aims The role of L-histidine (L-His) in nickel (Ni) hyperaccumulation is not well known. The present study aimed to understand the impact of L-His on Ni translocation and Ni toxicity in shoots of Odontarrhena inflata and Aurinia saxatilis. Methods In the preliminary experiments, the Ni content of plants was quantified in pretreated plants using L-histidine and L-alanine (L-Ala) for 4 hours and then exposed to Ni for 8 hours. Hydrogen peroxide (H2O2) and activity of some antioxidant enzymes were determined after 4 hours of pretreatment using L-His and L-Ala before 48 hours Ni treatments. Results L-histidine increased Ni translocation to shoots in O. inflata and A. saxatilis. Ni increased the activity of POD, APX, and CAT in both species, but the higher activity of APX and CAT in O. inflata. Ni revealed a concentration-dependent increase in H2O2 content in A. saxatilis. L-His pretreatment increased H2O2 concentration in Ni-treated plants. Pretreatment with L-His decreased the activity of POD, APX, and CAT only at 300 µM Ni in O. inflata while decreasing the activity of CAT, but increased POD activity at 150 and 300 µM Ni in A. saxatilis. Pretreatment with L-Ala decreased POD and APX activity but had no significant impact on H2O2 content and CAT activity. Conclusion L-Histidine promoted root-to-shoot Ni translocation and alleviated Ni toxicity by inducing of antioxidant enzymes in hyperaccumulator and non-accumulator plants. The role of histidine in Ni hyperaccumulation may not be limited to Ni transport, but linked to detoxification of Ni.