The Dynamic Changes of the Plasma Membrane Proteins and the Protective Roles of Nitric Oxide in Rice Subjected to Heavy Metal Cadmium Stress.

Liming Yang,Hongliang Wang,Xiangyang Hu,Karen R Harris-Shultz,Yuming Luo,Hui Wang,Jianhui Ji,Elsayed F Abd-Allah

doi:10.3389/fpls.2016.00190

Abstract

The heavy metal cadmium is a common environmental contaminant in soils and has adverse effects on crop growth and development. The signaling processes in plants that initiate cellular responses to environmental stress have been shown to be located in the plasma membrane (PM). A better understanding of the PM proteome in response to environmental stress might provide new insights for improving stress-tolerant crops. Nitric oxide (NO) is reported to be involved in the plant response to cadmium (Cd) stress. To further investigate how NO modulates protein changes in the plasma membrane during Cd stress, a quantitative proteomics approach based on isobaric tags for relative and absolute quantification (iTRAQ) was used to identify differentially regulated proteins from the rice plasma membrane after Cd or Cd and NO treatment. Sixty-six differentially expressed proteins were identified, of which, many function as transporters, ATPases, kinases, metabolic enzymes, phosphatases, and phospholipases. Among these, the abundance of phospholipase D (PLD) was altered substantially after the treatment of Cd or Cd and NO. Transient expression of the PLD fused with green fluorescent peptide (GFP) in rice protoplasts showed that the Cd and NO treatment promoted the accumulation of PLD in the plasma membrane. Addition of NO also enhanced Cd-induced PLD activity and the accumulation of phosphatidic acid (PA) produced through PLD activity. Meanwhile, NO elevated the activities of antioxidant enzymes and caused the accumulation of glutathione, both which function to reduce Cd-induced H2O2 accumulation. Taken together, we suggest that NO signaling is associated with the accumulation of antioxidant enzymes, glutathione and PA which increases cadmium tolerance in rice via the antioxidant defense system.

Highlights

The heavy metal cadmium is a common environmental contaminant with a long biological half-life in the soil and has adverse effects on crop growth and development (Das et al, 1997; Tuan Anh and Popova, 2013; Choppala et al, 2014)
By directly measuring the nitric oxide (NO) content in the roots, we found that Cd treatment increased the NO content as compared to control plants, but this increase could be suppressed by the NO scavenger cPTIO treatment (Figure 3B)
We found that Cd or Cd+SNAP treatments increased the level of phospholipase D (PLD) protein in the plasma membrane (Figure 5B) and partially increased the total PLD protein level in the total protein (Figure 5C)

Summary

Introduction

The heavy metal cadmium is a common environmental contaminant with a long biological half-life in the soil and has adverse effects on crop growth and development (Das et al, 1997; Tuan Anh and Popova, 2013; Choppala et al, 2014). Cadmium is absorbed by plant roots and is quickly transported to the leaves via the xylem. Most plants are very sensitive to trace amounts of cadmium, responding with retardation in growth and development, due to decreased photosynthesis in the leaves. This impairs photosynthetic supply and accelerates apoptosis and necrosis of the leaves. NO is required for cadmium-induced programmed cell death in Arabidopsis (Balestrasse et al, 2006; De Michele et al, 2009)

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Discussion

Conclusion