Epichloë Endophyte Modifies Antioxidative Defense and Aquaporin Genes Expression in Response to Ni Contamination in Lolium perenne

The aim of this study was to determine the impacts of endophyte (E) inoculation on Nickel tolerance of the Lolium prenne by measuring the physiological and biochemical traits in two populations of ryegrass consisting both (E-) and (E+) plants cultivated under Ni stress. The plants were grown in a Ni polluted soil at 0, 30, 90 and 180 mg Ni kg -1. The present research showed that the activity of antioxidant enzymes increased in Ni treated plants in contrast to control plants; whereas the activity of glutathione reductase enzyme decreased. Also, endophyte infection increased the activity of some antioxidant enzymes but decreased the activity of SOD enzyme. Upregulation of aquaporin gene (LpTIP1;1) was shown in population 1 E+ plants at all treatments and 30 ppm Ni in E- plants, whereas, the expression of LpTIP1;2 in population 1 E- plants increased and no significant difference was shown for E+ plants. After 3 months from treating plants, considerable reduction in shoot biomass of E+ and E- plants was observed in 180 ppm Ni and endophyte inoculation decreased the biomass of plants. The shoot water content of E- plants was greater than E+ counterparts. A significant increase of Ni concentration of roots and shoots was also observed under Ni stress and the Ni concentration of E+ plants was 88.7% and 12.7% greater in shoots and roots, respectively, than in E- plants. Overall, results suggest that variation in response to Ni stress in E+ and E- ryegrass populations may aid survival of the grass under stress conditions.