Journal Article

Exogenous Abscisic Acid Alleviates Cadmium Toxicity by Restricting Cd super(2+) Influx in Populus euphratica Cells

Zhao, Nan, Wang, Shaojie, Yi, Huilan, Chen, Shaoliang, Deng, Shurong, Li, Nianfei, Shen, Xin, Zhao, Chenjing, Han, Yansha, Zhao, Rui, Sun, Jian

2016

Overview

Abscisic acid (ABA), a widely known phytohormone involved in the plant response to abiotic stress, plays a vital role in mitigating Cd super(2+) toxicity in herbaceous species. However, the role of ABA in ameliorating Cd super(2+) toxicity in woody species is largely unknown. In the present study, we investigated ABA restriction on Cd super(2+) uptake and the relevance to Cd super(2+) stress alleviation in Cd super(2+)-hypersensitive Populus euphratica. ABA (5 mu M) markedly improved cell viability and growth but reduced membrane permeability in CdCl sub(2) (100 mu M)-stressed P. euphratica cells. Moreover, ABA significantly increased the activity of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX), contributing to the scavenging of Cd super(2+)-elicited H sub(2)O sub(2) within P. euphratica cells during the period of CdCl sub(2) exposure (100 mu M, 24-72 h). ABA alleviation of Cd super(2+) toxicity was mainly the result of ABA restriction of Cd super(2+) uptake under Cd super(2+) stress. Steady-state and transient flux recordings showed that ABA inhibited Cd super(2+) entry into Cd super(2+)-shocked (100 mu M, 30 min) and short-term-stressed P. euphratica cells (100 mu M, 24-72 h). Non-invasive micro-test technique data showed that H sub(2)O sub(2) (3 mM) stimulated the Cd super(2+)-elicited Cd super(2+) influx but that the plasma membrane (PM) Ca super(2+) channel inhibitor LaCl sub(3) blocked it, suggesting that the Cd super(2+) influx was through PM Ca super(2+)-permeable channels. These results suggested that ABA up-regulated antioxidant enzyme activity in Cd super(2+)-stressed P. euphratica and that these enzymes scavenged the Cd super(2+)-elicited H sub(2)O sub(2) within cells. The entry of Cd super(2+) through the H sub(2)O sub(2)-mediated Ca super(2+)-permeable channels was subsequently restricted; thus, Cd super(2+) buildup and toxicity were reduced in the Cd super(2+)-hypersensitive species, P. euphratica.

• Subject: Populus