Unser 10. Leibniz Plant Biochemistry Symposium am 7. und 8. Mai war ein großer Erfolg. Thematisch ging es in diesem Jahr um neue Methoden und Forschungsansätze der Naturstoffchemie. Die exzellenten Vorträge über Wirkstoffe…
Omanische Heilpflanze im Fokus der Phytochemie IPB-Wissenschaftler und Partner aus Dhofar haben jüngst die omanische Heilpflanze Terminalia dhofarica unter die phytochemische Lupe genommen. Die Pflanze ist reich an…
Geschmack ist vorhersagbar: Mit FlavorMiner. FlavorMiner heißt das Tool, das IPB-Chemiker und Partner aus Kolumbien jüngst entwickelt haben. Das Programm kann, basierend auf maschinellem Lernen (KI), anhand der…
Frick, S.; Kramell, R.; Schmidt, J.; Fist, A. J.; Kutchan, T. M.;Comparative Qualitative and Quantitative Determination of Alkaloids in Narcotic and Condiment Papaver somniferum CultivarsJ. Nat. Prod.68666-673(2005)DOI: 10.1021/np0496643
In the present study morphinan, tetrahydrobenzylisoquinoline, benzo[c]phenanthridine, and phthalideisoquinoline alkaloids were determined qualitatively and quantitatively by HPLC and LC-MS analysis in tissues of the Tasmanian Papaver somniferum L. elite cultivar C048-6-14-64. The data were compared with the results from the low-morphine cultivar “Marianne”. In the elite cultivar, 91.2% of the latex alkaloids consist of the three pharmaceutically most valuable alkaloids: morphine, codeine, and thebaine. In the root system, the major alkaloids are sanguinarine/10-hydroxysanguinarine and dihydrosanguinarine/10-hydroxydihydrosanguinarine. In the stems and leaves of C048-6-14-64, the same alkaloids were measured as in the latex. In the stems, a gradient in relative total alkaloid content from the top downward toward the roots was observed. The concentration of morphine was decreasing toward the roots, whereas an increasing gradient from the upper to the lower stem parts was detected for codeine. The relative total alkaloid concentration in leaves remained constant; no gradient was observed. The cultivar “Marianne” displayed a shifted pattern of alkaloid accumulation and reduced levels of total alkaloid. In the condiment cultivar, 80.5% of the alkaloids of the latex consisted of the two phthalideisoquinoline alkaloids narcotoline and noscapine. Only 18.8% of the relative total alkaloid content were morphinan alkaloids. In contrast to the narcotic cultivar, in which the benzo[c]phenanthridines in roots dominated over the morphinan and tetrahydrobenzylisoquinoline alkaloids, the concentration of benzo[c]phenanthridines in “Marianne” was similar to that of morphinan and tetrahydrobenzylisoquinoline alkaloids. These data suggest a differential alkaloid regulation in each cultivar of P. somniferum.
Publikation
Page, J. E.; Hause, G.; Raschke, M.; Gao, W.; Schmidt, J.; Zenk, M. H.; Kutchan, T. M.;Functional Analysis of the Final Steps of the 1-Deoxy-d-xylulose 5-phosphate (DXP) Pathway to Isoprenoids in Plants Using Virus-Induced Gene SilencingPlant Physiol.1341401-1413(2004)DOI: 10.1104/pp.103.038133
Isoprenoid biosynthesis in plant plastids occurs via the 1-deoxy-d-xylulose 5-phosphate (DXP) pathway. We used tobacco rattle virus (TRV) to posttranscriptionally silence the expression of the last two enzymes of this pathway, the IspG-encoded (E)-4-hydroxy-3-methylbut-2-enyl diphosphate synthase (HDS) and the IspH-encoded isopentenyl/dimethylallyl diphosphate synthase (IDDS), as well as isopentenyl/dimethylallyl diphosphate isomerase (IDI), the enzyme that interconverts IPP and DMAPP. TRV-IspG and TRV-IspH infected Nicotiana benthamiana plants had albino leaves that contained less than 4% of the chlorophyll and carotenoid pigments of control leaves. We applied [13C]DXP and [14C]DXP to silenced leaves and found that 2-C-methyl-d-erythritol 2,4-cyclodiphosphate accumulated in plants blocked at HDS while DXP, (E)-4-hydroxy-3-methylbut-2-enyl phosphate and (E)-2-methylbut-2-ene-1,4-diol accumulated in IDDS-blocked plants. Albino leaves from IspG- and IspH-silenced plants displayed a disorganized palisade mesophyll, reduced cuticle, fewer plastids, and disrupted thylakoid membranes. These findings demonstrate the participation of HDS and IDDS in the DXP pathway in plants, and support the view that plastid isoprenoid biosynthesis is metabolically and physically segregated from the mevalonate pathway. IDI-silenced plants had mottled white-pale green leaves with disrupted tissue and plastid structure, and showed an 80% reduction in pigments compared to controls. IPP pyrophosphatase activity was higher in chloroplasts isolated from IDI-silenced plants than in control plant chloroplasts. We suggest that a low level of isoprenoid biosynthesis via the DXP pathway can occur without IDI but that this enzyme is required for full function of the DXP pathway.