Compartmentalization and Excretion of 2,4,6-Tribromophenol Sulfation and Glycosylation Conjugates in Rice Plants

Abstract

The most environmentally abundant bromophenol congener, 2,4,6-tribromophenol (2,4,6-TBP, 6.06 μmol/L), was exposed to rice for 5 d both in vivo (intact seedling) and in vitro (suspension cell) to systematically characterize the fate of its sulfation and glycosylation conjugates in rice. The 2,4,6-TBP was rapidly transformed to produce 6 [rice cells (3 h)] and 8 [rice seedlings (24 h)] sulfated and glycosylated conjugates. The predominant sulfation conjugate (TP408, 93.0–96.7%) and glycosylation conjugate (TP490, 77.1–90.2%) were excreted into the hydroponic solution after their formation in rice roots. However, the sulfation and glycosylation conjugates presented different translocation and compartmentalization behaviors during the subsequent Phase III metabolism. Specifically, the sulfated conjugate could be vertically transported into the leaf sheath and leaf, while the glycosylation conjugates were sequestered in cell vacuoles and walls, which resulted in exclusive compartmentalization within the rice roots. These results showed the micromechanisms of the different compartmentalization behaviors of 2,4,6-TBP conjugates in Phase III metabolism. Glycosylation and sulfation of the phenolic hydroxyl groups orchestrated by plant excretion and Phase III metabolism may reduce the accumulation of 2,4,6-TBP and its conjugates in rice plants.

Rapid plant uptake of isothiazolinone biocides and formation of metabolites by hydroponic Arabidopsis

“…30,31 Some xenobiotics, e.g. 2,4,6-tribromophenol with its hydroxyl group in the parent compound, 32 can proceed directly to Phase II metabolism without rst undergoing Phase I metabolism. Thus, the functional group chemistry of the parent compound is important to plant metabolism.…”

“…29,31 Nevertheless, recent evidence demonstrates that some xenobiotic compounds do not follow all the phases of classical plant metabolism. For example, recent evidence indicates that conjugated metabolites can subsequently deconjugate 33,34 and/ or be excreted from the plant, [25][26][27]32,[35][36][37] presenting previously unknown exposure routes. Additionally, amino-acid conjugated xenobiotics may closely resemble natural plant compounds and be incorporated into those biosynthesis pathways rather than simply being sequestered.…”

Biotic and Abiotic Transformation Pathways of a Short-Chain Chlorinated Paraffin Congener, 1,2,5,6,9,10-C10H16Cl6, in a Rice Seedling Hydroponic Exposure System

“…Glycosylation metabolites with glucose and glucuronic acid groups could be formed under the catalysis of O-glucosyltransferase. 33,43,44 Hence, M 491 , M 471 , and M 487 were deduced as the products of direct glycosylation of monohydroyxlation compounds, M 329 , M 295 , and M 311 . The other glucose conjugate metabolites M 507 and M 523 were hydroxylated from M 491 in sequence, and M 489 was hydroxylated from M 473 .…”

Bromophenol Induced Multiple Stress Responses in Rice Plants: Impact of Doses and Congener Structures

“…Plant uptake of emerging contaminants has generally resulted in unintended oxidative damage and eventually led to inhibition of plant growth and even cell death. − For example, halogenated phenols (e.g., 4-chlorophenol and 2,4-dichlorophenol) can inhibit seed germination and plant transpiration. , With regard to the phytotoxicity of xenobiotics, transferase enzymes (i.e., glycosyltransferase, sulfotransferase, and glutathione S-transferases) are appended glucuronyl, sulfonyl, and glutathionyl groups to hydroxyl, thiols, and amine groups to form more polar metabolites in phase II metabolism. , Glycosyltransferases mediate the glycosylation process of phenolic contaminants in various plants and yield numerous glycoconjugates. Notably, 6–23 glycoconjugates have been observed for triclosan, tetrabromobisphenol A, and 2,4,6-TriBP in carrots, pumpkins, and rice plants. − Subsequently, the excretion of conjugates of xenobiotics (phase III metabolism) is orchestrated with other processes to conduct the detoxifcation . Our previous studies have illustrated that in both suspension rice cells and seedlings, several glycoconjugates were formed in 2,4,6-TriBP exposure systems at relatively high concentrations. , The coordination of glycosylation-related genes, glycosyltransferases, and glycosylation processes responding to BPs stress at different concentrations remains obscure.…”

“…Notably, 6–23 glycoconjugates have been observed for triclosan, tetrabromobisphenol A, and 2,4,6-TriBP in carrots, pumpkins, and rice plants. − Subsequently, the excretion of conjugates of xenobiotics (phase III metabolism) is orchestrated with other processes to conduct the detoxifcation . Our previous studies have illustrated that in both suspension rice cells and seedlings, several glycoconjugates were formed in 2,4,6-TriBP exposure systems at relatively high concentrations. , The coordination of glycosylation-related genes, glycosyltransferases, and glycosylation processes responding to BPs stress at different concentrations remains obscure. Additionally, the O -glycosylation of BPs among different types of congeners is not clear.…”