鎵對阿拉伯芥生理以及分子層面上的影響

Abstract

Gallium (Ga) is a semimetallic element that has been progressively used in making electronics. The environmental contamination of gallium chemicals raises potential impacts on the ecology and human health. The information regarding how gallium interacts with plants is relatively insufficient in literatures. In this study, we demonstrate both the physiological and molecular basis of Ga exposure in the model plant Arabidopsis thaliana. Seedlings exposure to 6-150 µM Ga(NO3)3 had no effect on plant biomass and only slight reduction (15%) on root elongation. However, at 250 and 500 µM of Ga, the fresh weight and the root length were significantly reduced by nearly 30% and 60%, respectively. Malondialdehyde (MDA) production, a measure of lipid peroxidation, was unaffected under 6-500 µM Ga(NO3)3 exposure but increased by 2.5-fold at 750 µM, suggesting that Ga stress has potential to cause oxidative damage in plants. No significant accumulation of Ga was detected in plants grown below 150 µM Ga(NO3)3. In addition, the Ga concentration in the root (1000 mg kg-1 DW) was higher than in the shoot (200 mg kg-1 DW) under 500 µM Ga(NO3)3, indicating the immobilization or limited translocation of Ga in plants. With analysis of Ca, Mg, K, Na, P, N, Fe, Mn and Zn contents, we found that only Fe accumulation was reduced under Ga treatments. It implies that Ga perturbs Fe homeostasis in plants. By monitoring the expression of Fe deficiency related genes, we found that Ga might interfere the upstream molecule(s) of Fe homeostasis to reduce the activity of Fe deficiency signaling regulatory networks. Furthermore, we demonstrate that supplying exogenous citrate significantly increased Ga tolerance in Arabidopsis, which might be a potential way to remediate Ga-contaminated soil in the future.