Biomonitoring of Non-Dioxin-Like Polychlorinated Biphenyls in Transgenic Arabidopsis Using the Mammalian Pregnane X Receptor System: A Role of Pectin in Pollutant Uptake

Lieming Bao,Hongwu Bian,Weiqiang Lin,Ning Han,Yanjun Yang,Chen Gao,Yong Chen,Miaomiao Li,Muyuan Zhu,Junhui Wang,Sunghun Park

doi:10.1371/journal.pone.0079428

Abstract

Polychlorinated biphenyls (PCBs) are persistent organic pollutants damaging to human health and the environment. Techniques to indicate PCB contamination in planta are of great interest to phytoremediation. Monitoring of dioxin-like PCBs in transgenic plants carrying the mammalian aryl hydrocarbon receptor (AHR) has been reported previously. Herein, we report the biomonitoring of non-dioxin-like PCBs (NDL-PCBs) using the mammalian pregnane X receptor (PXR). In the transgenic Arabidopsis designated NDL-PCB Reporter, the EGFP-GUS reporter gene was driven by a promoter containing 18 repeats of the xenobiotic response elements, while PXR and its binding partner retinoid X receptor (RXR) were coexpressed. Results showed that, in live cells, the expression of reporter gene was insensitive to endogenous lignans, carotenoids and flavonoids, but responded to all tested NDL-PCBs in a dose- and time- dependent manner. Two types of putative PCB metabolites, hydroxy- PCBs and methoxy- PCBs, displayed different activation properties. The vascular tissues seemed unable to transport NDL-PCBs, whereas mutation in QUASIMODO1 encoding a 1,4-galacturonosyltransferase led to reduced PCB accumulation in Arabidopsis, revealing a role for pectin in the control of PCB translocation. Taken together, the reporter system may serve as a useful tool to biomonitor the uptake and metabolism of NDL-PCBs in plants.

Highlights

Polychlorinated biphenyls (PCBs) are a class of chlorinated aromatic hydrocarbon chemicals that were used worldwide as heat-exchanger, transformer, and hydraulic fluids from the 1930s to the early 1980s [1]
Arabidopsis plants were co-transformed with the EGFP-GUS reporter gene construction (Fig. 1a) and the pregnane X receptor (PXR)/retinoid X receptor (RXR) receptor and binding partner construction (Fig. 1c, d)
We found that young Arabidopsis seedlings of NDL-PCB Reporters displayed no background GUS activities on the medium without NDL-PCBs (Fig. 2a, c), indicating that the expression of the reporter gene was insensitive to endogenous PXR ligands

Summary

Introduction

Polychlorinated biphenyls (PCBs) are a class of chlorinated aromatic hydrocarbon chemicals that were used worldwide as heat-exchanger, transformer, and hydraulic fluids from the 1930s to the early 1980s [1]. Different types of PCBs, known as congeners, are distinguished by the number of chlorine atoms and their location on the biphenyl ring structure. These congeners can be divided into two major groups, namely dioxin-like and non-dioxin-like PCBs [8,9]. Dioxin-like PCBs (DL-PCBs) have one or no chlorine atoms at the ortho-positions and adopt a more coplanar structure. Non-dioxinlike PCBs (NDL-PCBs) have at least two chlorine substitutions at the ortho-positions and are less coplanar

Methods

Results

Conclusion