title: Immunolocalisation of two tropinone reductases in potato (Solanum tuberosum L.) root, stolon, and tuber sprouts.
abstract: Tropinone reductases (TRs) are essential enzymes in the tropane alkaloid biosynthesis, providing either tropine for hyoscyamine and scopolamine formation or providing pseudotropine for calystegines. Two cDNAs coding for TRs were isolated from potato (Solanum tuberosum L.) tuber sprouts and expressed in E. coli. One reductase formed pseudotropine, the other formed tropine and showed kinetic properties typical for tropine-forming tropinone reductases (TRI) involved in hyoscyamine formation. Hyoscyamine and tropine are not found in S. tuberosum plants. Potatoes contain calystegines as the only products of the tropane alkaloid pathway. Polyclonal antibodies raised against both enzymes were purified to exclude cross reactions and were used for Western-blot analysis and immunolocalisation. The TRI (EC 1.1.1.206) was detected in protein extracts of tuber tissues, but mostly in levels too low to be localised in individual cells. The function of this enzyme in potato that does not form hyoscyamine is not clear. The pseudotropine-forming tropinone reductase (EC 1.1.1.236) was detected in potato roots, stolons, and tuber sprouts. Cortex cells of root and stolon contained the protein; additional strong immuno-labelling was located in phloem parenchyma. In tuber spouts, however, the protein was detected in companion cells.
authors.affiliation: Institute of Pharmaceutical Biology and Pharmacology, Martin-Luther-University Halle-Wittenberg, Hoher Weg 8, 06120 Halle/Saale, Germany.
authors.forename: Heike
authors.initials: H
authors.lastname: Kaiser
authors.forename: Ute
authors.initials: U
authors.lastname: Richter
authors.forename: Ronald
authors.initials: R
authors.lastname: Keiner
authors.forename: Anja
authors.initials: A
authors.lastname: Brabant
authors.forename: Bettina
authors.initials: B
authors.lastname: Hause
authors.forename: Birgit
authors.initials: B
authors.lastname: Dräger
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D000595:Amino Acid Sequence; D001285:Atropine / Q000378:metabolism; D015153:Blotting, Western; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D007150:Immunohistochemistry; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism*; D035281:Plant Tubers / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D011198:Solanum tuberosum / Q000201:enzymology* / Q000235:genetics; D014326:Tropanes / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D011994:Recombinant Proteins; D014326:Tropanes; D001285:Atropine; C005864:tropine; D000429:Alcohol Oxidoreductases; C083753:tropinone reductase