Exogenously added naphthols induce three glucosyltransferases, and are accumulated as glucosides in tobacco cells

Plants detoxify and accumulate several compounds as glucosides. In this work, detoxification of the exogenously added harmful compound naphthol in tobacco cells (Nicotiana tabacum L. Bright Yellow) was studied. When 250 muM of 1-naphthol or 2-naphthol was added to the tobacco cells, most of the naphthol was accumulated in the cell as glucosides and in further modified forms. The glucosylation activities against naphthols were increased in proportion to the concentration of naphthols in the culture medium. Addition of I mM naphthols caused cell death. Three glucosyltransferase genes, namely NtGT1a, NtGT1b and NtGT3 were isolated and characterized. The recombinant enzymes encoded by these genes showed glucosylation activity against naphthols and other phenolic compounds. It was also shown that these genes were induced following the addition of naphthols to the tobacco cells. These results suggest that naphthols are metabolized by glucosyltransferases whose production is inducible by naphthol itself. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.