Functional importance of the family 1 glucosyltransferase UGT72B1 in the metabolism of xenobiotics in Arabidopsis thaliana

Abstract

SummaryThe Arabidopsis type 1 UDP-glucose-dependent glucosyltransferase UGT72B1 is highly active in conjugating the persistent pollutants 3,4-dichloroaniline (DCA) and 2,4,5-trichlorophenol (TCP). To determine its importance in detoxifying xenobiotics in planta, mutant plants where the respective gene has been disrupted by T-DNA insertion have been characterized. Extracts from the knockout ugt72B1 plants showed radically reduced conjugating activity towards DCA and TCP and the absence of immunodetectable UGT72B1 protein. In contrast, activities towards phenolic natural products were unaffected. When aseptic root cultures were fed [ 14 C]-DCA, compared with wild types, the ugt72B1 plants showed a reduced rate of uptake of the xenobiotic and very little metabolism to soluble DCA-glucose or associated polar conjugates. Instead, the knockouts accumulated non-extractable radioactive residues, most probably associated with lignification. When the feeding studies were carried out with [14 C]-TCP, rates and routes of metabolism were identical in the wild type and knockouts, with TCP-glucoside a major product in both cases. Similar differential effects on the metabolism of DCA and TCP were obtained in whole plant studies with wild type and ugt72B1 mutants, demonstrating that while UGT72B1 had a central role in metabolizing chloroanilines in Arabidopsis, additional UGTs could compensate for the conjugation of TCP in the knockout. TCP was equally toxic to wild type and ugt72B1 plants, while surprisingly, the knockouts were less sensitive to DCA. From this it was concluded that the glucosylation of DCA may not be as effective in xenobiotic detoxification as bound-residue formation.

Recombinant expression and functional characterisation of regiospecific flavonoid glucosyltransferases from Hieracium pilosella L.

“…Besides the arbutin synthase from R. serpentina (Hefner et al 2002) mentioned above, subfamily 72 contains A. thaliana glucosyltransferases, including UGT72B1, which possesses both N-and O-glucosyltransferase activity. This enzyme was assigned to the detoxiWcation of xenobiotics (Loutre et al 2003;Brazier-Hicks and Edwards 2005;Brazier-Hicks et al 2007), whereas the UGTs 72E1-E3 are involved in the glucosylation of monolignols, hydroxycinnamic acids, and hydroxycinnamic aldehydes Lanot et al 2006). H. pilosella UGT90A7 belongs to group C and, to the best of our knowledge, an enzyme of this subfamily has never been characterised.…”

Characterization and engineering of the bifunctional N - and O -glucosyltransferase involved in xenobiotic metabolism in plants

“…2, Table 1). TCP was chosen, because studies with Arabidopsis protein extracts have shown it to be an excellent glucose acceptor (6). In each case, the specific activities of the UGTs were determined after quantifying the fusion protein.…”

“…Several UDP-glc-dependent glycosyltransferases (UGTs) in Arabidopsis have been shown to have O-glucosyltransferase (OGT) activity toward TCP (5), whereas only one enzyme, UGT72B1, was identified when N-glucosyltransferases (NGTs) active toward DCA were purified from suspension cultures (4). The importance of UGT72B1 in DCA metabolism in planta was subsequently demonstrated by using transposon-disrupted ugt72b1 knockouts (6). Plants lacking UGT72B1 metabolized DCA more slowly than wild types and, instead of accumulating N-glycosidic conjugates, incorporated the xenobiotic into insoluble macromolecules in phase 4 reactions (Fig.…”

“…The widespread N-glucosylation of DCA in plants (8) indicates that the activity catalyzed by UGT72B1 is important in regulating the metabolism of anilines in crops (6,9). Furthermore, the formation of C-N glycosidic bonds is of potential interest as a chemoenzymatic route to generate nonhydrolyzable glycosides.…”

Respuesta transcripcional de Populus a bifenilos policlorados: Aspectos aplicados a la fitorremediación

“…Esta comprobado que en presencia de un contaminante se forma un complejo con la molécula de GST, la cual interactúa con enzimas que facilitan su degradación, como la glutaminil-transpeptidasa (Brazier et al, 2005;. En el análisis de co-expresión se encontró un GST (GSTU25) (Potri.010G60900) que está relacionado con xenobióticos, por lo que es muy probable que esté relacionada con la detoxificación.…”