Amino Acid Transporter as a Potential Carrier Protein for the Root-to-Shoot Translocation of Polybrominated Diphenyl Ethers in Rice

Abstract

As typical persistent organic pollutants, polybrominated diphenyl ethers (PBDEs) tend to accumulate in edible parts of rice, posing great ecological and health risks. The translocation of PBDEs from underground to aboveground parts of rice is a crucial procedure to determine the final bioaccumulation level. Herein, this study aimed to identify the transporter proteins for PBDEs in rice plants in order to strengthen our understanding of the bioaccumulation mechanism and the potential prevention strategy of the PBDE risk. Similar time-dependent patterns were observed among the root-to-shoot translocation factors (TFs) of PBDEs, the expression of lysine histidine transporter (LHT) protein, and the relative levels of LHT substrates (phenylalanine or tyrosine), implying the potential co-transport of PBDEs, phenylalanine, and tyrosine by the carrier LHT. Fluorescence spectra and circular dichroism showed that PBDE congeners interfered with LHT via static fluorescence quenching and changes in the protein’s secondary structure. The in vitro sorption fraction of LHT to PBDEs, as revealed by sorption equilibrium analysis, was comparable to the in vivo TF values. Knockout of OsLHT1 in rice using CRISPR/Cas9 technology caused a 48.2–78.4% decrease in PBDE translocation. Molecular docking simulation suggested that PBDEs, phenylalanine, and tyrosine were inserted into the same ligand-binding cavity of LHT, substantiating the potential carrier role of LHT for PBDEs from a conformational perspective. Quantitative structure activity relationship analysis demonstrated that the ether-bond oxygen and the carbons at the site 4 and 4′ of PBDE molecules are significant determinants of the binding affinity with the LHT protein and in vivo translocation of PBDEs. In summary, this study discovered that LHT acts as the cellular carrier for PBDEs and offered a comprehensive molecular explanation for the bioaccumulation and translocation of PBDEs in rice plants, covering both biological and chemical perspectives. These findings fill in a knowledge gap on the endogenous transporter proteins for exogenous organic pollutants.

Novel Insights into Uptake, Translocation, and Transformation Mechanisms of 2,2′,4,4′-Tetra Brominated Diphenyl Ether (BDE-47) in Wheat (Triticum aestivum L.): Implication by Compound-Specific Stable Isotope and Transcriptome Analysis

“…As shown in Figure a, compared to roots (δ 13 C: −33.1 to −32.6‰), the δ 13 C values of BDE-47 in the shoots were overall higher during the whole period of incubation, with the ranges of −30.2 to −29.4‰ by considering measurement uncertainty of 0.5‰, indicating the enrichment in heavier isotopes during the translocation from roots to shoots. This phenomenon was also observed for translocation of hexachlorocyclohexane in the hydroponic and soil-wheat systems. , Due to the hindrance of endodermic Casparian strip, the compounds have to cross at least one lipid bilayer to enter the vascular bundle prior to the acropetal translocation from roots, and the transmembrane transport was depended on the channels and transporters of cell membrane. , Recently, Chen et al found that lysine histidine transporter protein acted as a cellular carrier for the root-to-shoot translocation of PBDEs in rice . In the present study, an energy-dependent active process was discovered by the inhibitors during the uptake of BDE-47 by wheat roots in addition to energy-free diffusion mediated by aquaporins and anion channels.…”

Quinolone Antibiotics Inhibit the Rice Photosynthesis by Targeting Photosystem II Center Protein: Generational Differences and Mechanistic Insights

“…Molecular docking, a computational technique based on principles of spatial arrangement and energy complementarity, − is commonly utilized to forecast the affinity between chemical entities (ligands) and biomolecules (receptors), , thereby playing a key role in unraveling the toxicity mechanisms posed by environmental contaminants. In this study, the interaction between three generations of antibiotics and the psbD protein was performed via a comparative molecular docking simulation.…”

Benzotriazole Ultraviolet Stabilizers (BUVSs) as Potential Protein Kinase Antagonists in Rice

“…In vitro competition binding experiments were first performed based on the equilibrium dialysis, which has been widely applied to evaluate the binding affinities of drug compounds with proteins. , The sorption of BUVSs and ATP to the dialysis bags was negligible (0.12–1.27%) (Figure S6). However, BUVSs and ATP were found to be significantly sorbed to CDPK in the individual sorption experiments (Figure S7), with the saturated sorption fractions (mean value) of 26.2–28.3 and 26.8%, respectively, when the initial concentration of chemicals was 75 μM and the incubation duration was 24 h (Figure S8).…”