Response of phase II detoxification enzymes in Phragmites australis plants exposed to organochlorines

Abstract

Mixed pollution is a characteristic of many industrial sites and constructed wetlands. Plants possessing an enzymatic detoxifying system that is able to handle xenobiotics seems to be a viable option for the removal of mixed persistent contaminants such organochlorines (OCs: monochlorobenzene (MCB), 1,4-dichlorobenzene (DCB), 1,2,4-trichlorobenzene (TCB), γ-hexachlorocyclohexane (HCH)). In this study, Phragmites australis plants were exposed to sub-lethal concentrations of OCs (7 days), in single-exposure (0.8 to 10 mg l(-1)) and in mixture of OCs (0.2 mg l(-1) MCB + 0.2 mg l(-1) DCB + 2.5 mg l(-1) TCB + 0.175 mg l(-1) HCH). Studies were conducted on the detoxification phase II enzymes; glutathione S-transferases (GST), and glucosyltransferases (UGT). Measurements of GST and UGT activities revealed that OCs may be buffered by glutathione and glucose conjugation. There appeared to be a correlation between the effects on phase II enzymes and the degree of chlorination of the benzene ring with, for example, the greatest effects being obtained for HCH exposure. In the case of mixed pollution, the induction of some GST isoenzymes (CDNB, 35 % non-significant) and UGT (118 %) in leaves and the inhibition of phase II enzymes in the other organs were measured. UGTs appear to be key enzymes in the detoxification of OCs.

Detoxification of polycyclic aromatic hydrocarbons (PAHs) in Arabidopsis thaliana involves a putative flavonol synthase

“…In addition to transformation, toxins may be conjugated to glucose, malonyl, or glutathione by transferases, transforming them into more water-soluble compounds [30, 69, 71–75] that are then translocated into the vacuole or cell wall compartments [69, 76]. Interestingly in Arabidopsis , the expression of 12 glutathione transferases increase under phenanthrene exposure, including At4g02520 , At2g02930 , At1g02920 , and At1g02930 [34, 77].…”

A Comparative Analysis on the Physiological Effects of the Physical and Chemical Properties of the Trihalomethanes on Nutrient Levels, Oxidative Stress and Sterol Compositions of Leaf Oils in Solanum Lycopersicum Cultivars

“…These include: the rapid sequestration and partitioning of organohalogens to lipophyllic plant cuticles (Moeckel et al, 2007); phyto-reduction of organohalogens to less halogenated metabolites (Nzengung and Jeffers, 2001); phyto-oxidation of organohalogens to halo-ethanols or haloacetic acids (Reichenauer and Germida, 2008) and the assimilation of organohalogens as non-phytotoxic metabolites into plant tissues (Susarla et al, 2002). The role of plant oxygenase and dehalogenase enzymes on the isolation, structure and detoxification mechanisms of organohalogens was also reported (Wolfe and Hoehamer, 2003;Van Aken, 2011;San Miguel et al, 2013).…”

Nucleophilic aromatic substitution in chlorinated aromatic systems with a glutathione thiolate model

“…Specifically, chlorobenzene and polychlorobenzenes trigger an increase in GST expression in epithelial cells and GST activity to detoxify these xenobiotic agents . Conjugates of chloroaromatic compounds from the displacement of chloride by GSH have been isolated in a number of cases, including monochlorobenzene, dichlorobenzenes, trichlorobenzenes, hexachlorobenzenes, the fungicide chlorothalonil, and PCBs …”

“…Besides activated aromatic substrates, such reactions are known to also take place with polychlorobenzenes, [9,72,[124][125][126] chlorinated xenobiotics, [127][128][129] and polychlorobiphenyls (PCBs). [130][131][132][133][134] Even simple chlorobenzene, [72,[135][136][137] along with dichlorobenzenes and trichlorobenzenes, [72,124,135,[137][138][139] is reported to undergo nucleophilic aromatic substitution.…”

“…[136,[145][146][147][148][149][150][151] Conjugates of chloroaromatic compounds from the displacement of chloride by GSH have been isolated in a number of cases, including monochlorobenzene, dichlorobenzenes, trichlorobenzenes, hexachlorobenzenes, the fungicide chlorothalonil, and PCBs. [126,127,[135][136][137][138][139]146] Glutathione S-transferases from mammalian systems have been extensively studied. Although three membranebound GSTs have been identified, only one appears to be responsible for xenobiotic activity.…”