Copper-caused oxidative stress triggers the activation of antioxidant enzymes via ZmMPK3 in maize leaves.

Jianxia Liu,Jinxiang Wang,Riyu Wen,Shaochin Lee,Ricardo Aroca

doi:10.1371/journal.pone.0203612

Jianxia Liu, Jinxiang Wang + Show 3 more

Open Access

https://doi.org/10.1371/journal.pone.0203612

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Journal: PloS one	Publication Date: Sep 17, 2018
Citations: 86	License type: CC BY 4.0

Affiliation: Shanxi Datong University, Jiangsu Normal University

Abstract

Copper (Cu) is a necessary trace element participated in many physiological processes in plants. But excessive Cu2+ is toxic, which can activate intracellular signals that lead to cellular damage. The mitogen-activated protein kinase (MAPK) cascade is at the center of cell signal transduction and has been reported to be involved in stress-related signaling pathways. ZmMPK3, a kind of MAPKs in maize cells, can be activated by diverse abiotic stresses. In the present study, we investigated the effects of Cu2+ on hydrogen peroxide (H2O2) level, ZmMPK3 activity as well as the activities of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and ascorbic acid peroxidase (APX) using maize leaf as an experimental model. The results demonstrated that acute Cu2+ exposure for 24 hours led to rapid increases of H2O2 level and the increase in ZmMPK3 activity as well as the total activities of antioxidant enzymes SOD, CAT and APX. H2O2 scavenger, dimethylthiourea (DMTU), effectively inhibited the Cu2+-increased H2O2 level and the activity of ZmMPK3 as well as the activities of the antioxidant enzymes SOD, CAT and APX. Pre-treatment with the MAPK inhibitor, PD98059, significantly blocked the Cu2+-increased activities of ZmMPK3, CAT, APX and SOD, but didn’t affect the accumulation of H2O2. Our results suggest that Cu2+ causes oxidative stress to the maize leaves which then activates defense antioxidant enzymes via MAPK pathway. Thus, the signaling pathway is Cu2+—H2O2—ZmMPK3—antioxidant enzymes.

Highlights

Copper (Cu) is an essential trace element in plants, which participates in many physiological processes such as electron transport in photosynthesis and respiration, detoxication, and redox reaction [1]
It was observed that brown polymerization products were barely seen in the base of leave in the control plants, which indicated that the level of H2O2 was low (Fig 1A)
The results indicated that Cu2+ stress led to reactive oxygen species (ROS) production, which activated mitogen-activated protein kinase (MAPK) pathway including ZmMPK3 signal pathway

Summary

Introduction

Copper (Cu) is an essential trace element in plants, which participates in many physiological processes such as electron transport in photosynthesis and respiration, detoxication, and redox reaction [1]. Plants absorb Cu2+ from the soil through the root, which further reach the aboveground part of plants through the xylem vessels. These ions are sequestered in the cell walls, vacuoles and the Golgi apparatuses. The roles of H2O2 accumulation and ZmMPK3 activation under Cu stress through membrane transporter carriers [2]. High concentrations of Cu2+ are toxic, which can cause toxicity symptoms, severe root damage and plant growth inhibition [3]. [4] and Atha et al [5] reported that Cu2+ stress can alter the ion distribution of calcium, potassium and magnesium in the cucumber root and leaves, and inhibit leaf expand and photosynthesis. Excess Cu2+ is found to induce lipid peroxidation and promote potassium ion efflux in Arabidopsis seedlings [6]

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