The effect of L-histidine on nickel translocation and the activities of antioxidant enzymes in hyperaccumulator (Odontarrhena inflata) and non-accumulator (Aurinia saxatilis) plants

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 tolerance in Odontarrhena inflata and Aurinia saxatilis.Methods To determine the impact of L-His and L-alanine (L-Ala) on the shoot Ni accumulation, we quantified the Ni concentration in plants pretreated with amino acids for 4 h and then exposed to Ni for 8 h. Hydrogen peroxide (H2O2) and antioxidant enzymes activities were determined after 4 h of pretreatments and 48 h of 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 activities of APX and CAT were higher in O. inflata. Ni exposure increased the H2O2 concentration in A. saxatilis. L-His pretreatment did not decrease the H2O2 concentration in Ni-treated plants, but decreased the activity of POD, APX, and CAT only at 300 mu M Ni in O. inflata. In A. saxatilis, L-His pretreatment, decreased the activity of CAT, but increased POD activity at 150 and 300 mu M Ni. Pretreatment with L-Ala decreased POD and APX activity but had no significant impact on H2O2 concentration and CAT activity.Conclusion L-Histidine promoted root-to-shoot Ni translocation and alleviated Ni toxicity, possibly through inducing the activities of antioxidant enzymes, in hyperaccumulator and non-accumulator plants. Histidine might not only facilitate the Ni translocation, but also contribute to Ni tolerance, at least in A. saxatlilis.

Automated summary

L-histidine promotes root-to-shoot nickel translocation and alleviates nickel toxicity by inducing antioxidant enzyme activities, at least in Aurinia saxatilis. Meanwhile, L-alanine decreases POD and APX activity without significant impact on H2O2 concentration and CAT activity.