Abstract
Phenols are present in the environment and commonly in contact with humans and animals because of their wide applications in many industries. In a previous study, we reported that uridine diphosphate-glucose-dependent glucosyltransferase PtUGT72B1 from Populus trichocarpa has high activity in detoxifying trichlorophenol by conjugating glucose. In this study, more experiments were performed to determine the substrate specificity of PtUGT72B1 towards phenolic compounds. Among seven phenols tested, three were glucosylated by PtUGT72B1 including phenol, hydroquinone, and catechol. Transgenic Arabidopsis plants expressing the enzyme PtUGT72B1 showed higher resistance to hydroquinone and catechol but more sensitivity to phenol than wild type plants. Transgenic Pichia pastoris expressing PtUGT72B1 showed enhanced resistance to all three phenols. Compared with wild type Arabidopsis plants, transgenic Arabidopsis plants showed higher removal efficiencies and exported more glucosides of phenol, phenyl β-D-glucopyranoside, to the medium after cultured with the three phenols. Protein extracts from transgenic Arabidopsis plants showed enhanced conjugating activity towards phenol, hydroquinone and catechol. PtUGT72B1 showed much higher expression level in Pichia pastoris than in Arabidopsis plants. Kinetic analysis of the PtUGT72B1 was also performed.
Highlights
Phenols are widely distributed in the environment because of their various applications in several industrial processes
Among the seven phenols tested, PtUGT72B1 from P. trichocarpa was confirmed to catalyze the O-glucosylation of phenol, hydroquinone, and catechol when expressed in A. thaliana and P. pastoris
In comparison to WT plants, we found that PtUGT72B1 transgenic (PT) plants could tolerate higher concentrations of hydroquinone and catechol on plates but surprisingly displayed much lower tolerance to phenol
Summary
Phenols are widely distributed in the environment because of their various applications in several industrial processes. They can induce genotoxic [1], carcinogenic [2], and immunotoxic [3] effect. Hydroquinone can occur in several plant species or be artificially synthesized for wide commercial applications. Hydroquinone induces rats to produce renal tubule adenomas and to exacerbate spontaneous chronic progressive nephropathy [4]. Catechol can cause eczematous dermatitis in humans, depression of the central nervous system, and prolonged rise in blood pressure in animals. Many reactions can occur between catechol and biomolecules (DNA and proteins) or membranes, causing the latter to break, inactivate, or destruct [5]
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