Comparative Physiological and Proteomic Analysis Reveals the Leaf Response to Cadmium-Induced Stress in Poplar (Populus yunnanensis).

Yunqiang Yang,Yunqiang Yang,Yunqiang Yang,Xiong Li,Xiong Li,Xiong Li,Xiong Li,Yanli Zhou,Yanli Zhou,Yanli Zhou,Yanli Zhou,Chao Dong,Chao Dong,Chao Dong,Chao Dong,Yongping Yang,Yongping Yang,Yongping Yang,Jian Ren,Shihai Yang,Shihai Yang,Shihai Yang,Xudong Sun,Xudong Sun,Xudong Sun

doi:10.1371/journal.pone.0137396

Abstract

Excess amounts of heavy metals are important environmental pollutants with significant ecological and nutritional effects. Cdmium (Cd) is of particular concern because of its widespread occurrence and high toxicity. We conducted physiological and proteomic analyses to improve our understanding of the responses of Populus yunnanensis to Cd stress. The plantlets experienced two apparent stages in their response to Cd stress. During the first stage, transiently induced defense-response molecules, photosynthesis- and energy-associated proteins, antioxidant enzymes and heat shock proteins (HSPs) accumulated to enhance protein stability and establish a new cellular homeostasis. This activity explains why plant photosynthetic capability during this period barely changed. During the second stage, a decline of ribulose-1, 5-bisphosphate carboxylase (RuBisCO) and HSP levels led to imbalance of the plant photosynthetic system. Additionally, the expression of Mitogen-activated protein kinase 3 (MPK3), Mitogen-activated protein kinase 6 (MPK6) and a homeobox-leucine zipper protein was higher in the second stage. Higher expression of caffeoyl-CoA O-methyltransferase (CCoAOMT) may regulate plant cell wall synthesis for greater Cd storage. These genes may be candidates for further research and use in genetic manipulation of poplar tolerance to Cd stress.

Highlights

Heavy metals constitute an important and worrying form of environmental pollution primarily caused by the increased mining and industrial activities in the 19th and early 20th centuries [1,2,3]
These results suggest the Cd decreases the photosynthetic activity of P. yunnanensis with the prolongation of Cd stress time, especially after 4 days of treatment
Some proteins associated with protection and repair mechanisms related to the photochemical reaction pathway were differentially expressed, such as three RuBisCO proteins (Fig 2a, spots 49, 68 and 79) and glyceraldehyde 3-phosphate dehydrogenase (GADPH) (Fig 2a, spot 43), which were up-regulated in P. yunnanensis leaves during Cd treatment, with expression peaks at 4 and 8 d, respectively (Fig 2a and Table 1)

Summary

Introduction

Heavy metals constitute an important and worrying form of environmental pollution primarily caused by the increased mining and industrial activities in the 19th and early 20th centuries [1,2,3]. Fifty-three of the ninety naturally occurring elements are heavy metals [4]. Cd is of particular concern because of its widespread occurrence and high toxicity. A problem in some agricultural soils in China is the uptake of Cd by rice (Oryza sativa) and other crops grown on the acidic red soils of southern China [5,6]. The concentration of Cd in these soils exceeds the World Health Organization’s recommendations (0.2 ppm) [7]. Forest soils are more susceptible to Cd because they are often acidic, poorly buffered and exposed to atmospheric heavy-metal pollution [6]

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Discussion

Conclusion