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

Abstract

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 µM 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 1 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.

Cloning and characterization of a glucosyltransferase that reacts on 7-hydroxyl group of flavonol and 3-hydroxyl group of coumarin from tobacco cells

“…These values were the same as other plant GTases reported [14,23,27], suggesting that these substrates are reasonable sugar acceptors for the enzyme. Kaempferol but not 3-hydroxycoumarin is a natural compound in tobacco.…”

“…x 150 mm: LUNA 5u C18(2), Phenomenex, Torrance, CA) with an LC10Avp system (Shimadzu, Kyoto, Japan). Kaempferol and its glucoside were separated as described previously [23]. For the separation of 3-hydroxycoumarin and its glucoside, the column was eluted with solvent A (40 % methanol in 0.1 % HCOOH) for 12 min at a flow rate of 1 mL / min at 40 ºC.…”

“…Moreover, several GTase genes have been reported, namely, genes of IEGT, TOGT, jasmonate-inducible GTase gene (JIGT) [19], and salicylic acid GTase gene [20]. In our previous studies, the glucosylation activity in cultured tobacco cells was investigated [21][22][23]. We isolated GTase genes (NtGT1a, NtGT1b and NtGT3) whose encoding enzymes have glucosylation activity against many kinds of phenolics, such as flavonoids, coumarins and naphthols [22,23].…”

“…In our previous studies, the glucosylation activity in cultured tobacco cells was investigated [21][22][23]. We isolated GTase genes (NtGT1a, NtGT1b and NtGT3) whose encoding enzymes have glucosylation activity against many kinds of phenolics, such as flavonoids, coumarins and naphthols [22,23]. These enzymes glucosylate mainly on 3-OH of flavonoids.…”

Molecular cloning and characterization of coumarin glucosyltransferase in hairy roots of Pharbitis nil (Ipomoea nil)

“…Skimmin is a glucoside of umbelliferone, and it has shown very weak toxicity against PNHR . A similar detoxification method or defense system has been reported in A. thaliana and Nicotiana tabacum (Bowles et al 2005;Taguchi et al 2003a). In these reports, this detoxification system was controlled by a GTase.…”