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…
To explore the chemical composition of root exudates of the model plant Arabidopsis thaliana a workflow for nontargeted metabolite profiling of the semipolar fraction of root exudates was developed. It comprises hydroponic plant cultivation and sampling of root exudates under sterile conditions, sample preparation by solid-phase extraction and analysis by reversed-phase UPLC/ESI-QTOFMS. Following the established workflow, root exudates of six-week-old plants were profiled and a set of reproducibly occurring molecular features was compiled. To structurally elucidate the corresponding metabolites, accurate mass tandem mass spectrometry and on-line hydrogen/deuterium exchange were applied. Currently, a total of 103 compounds were detected and annotated by elemental composition of which more than 90 were structurally characterized or classified. Among them, 42 compounds were rigorously identified using an authenticated standard. The compounds identified so far include nucleosides, deoxynucleosides, aromatic amino acids, anabolites and catabolites of glucosinolates, dipeptides, indolics, salicylic and jasmonic acid catabolites, coumarins, mono-, di- and trilignols, hydroxycinnamic acid derivatives and oxylipins and exemplify the high chemical diversity of plant root exudates.
Publikation
Böttcher, C.; Roepenack-Lahaye, E. v.; Willscher, E.; Scheel, D.; Clemens, S.;Evaluation of Matrix Effects in Metabolite Profiling Based on Capillary Liquid Chromatography Electrospray Ionization Quadrupole Time-of-Flight Mass SpectrometryAnal. Chem.791507-1513(2007)DOI: 10.1021/ac061037q
The coupling of liquid chromatography to electrospray ionization quadrupole time-of-flight mass spectrometry can be a powerful tool for metabolomics, i.e., the comprehensive detection of low molecular weight compounds in biological systems. There have, however, been doubts about the feasibility and reliability of this approach, because LC−MSespecially with electrospray ionizationcan be subject to matrix effects. We evaluated matrix effects for our metabolomics platform in three ways: (i) postextraction addition of a set of reference compounds to different complex biological matrixes to determine absolute and relative matrix effects, (ii) postcolumn infusion of two reference compounds, and (iii) mixing of two complex matrixes. Our data demonstrate that there are indeed significant absolute matrix effects when comparing highly divergent samples. However, relative matrix effects are negligibleunless extremely divergent matrixes are comparedand do not compromise the relative quantification that is aimed for in nontargeted metabolomics studies. In conclusion, employing LC-coupled ESI-QTOF-MS for metabolomics studies is feasible yet rigorous validation is necessary.
Publikation
Landtag, J.; Baumert, A.; Degenkolb, T.; Schmidt, J.; Wray, V.; Scheel, D.; Strack, D.; Rosahl, S.;Accumulation of tyrosol glucoside in transgenic potato plants expressing a parsley tyrosine decarboxylasePhytochemistry60683-689(2002)DOI: 10.1016/S0031-9422(02)00161-9
As part of the response to pathogen infection, potato plants accumulate soluble and cell wall-bound phenolics such as hydroxycinnamic acid tyramine amides. Since incorporation of these compounds into the cell wall leads to a fortified barrier against pathogens, raising the amounts of hydroxycinnamic acid tyramine amides might positively affect the resistance response. To this end, we set out to increase the amount of tyramine, one of the substrates of the hydroxycinnamoyl-CoA:tyramine N-(hydroxycinnamoyl)-transferase reaction, by placing a cDNA encoding a pathogen-induced tyrosine decarboxylase from parsley under the control of the 35S promoter and introducing the construct into potato plants via Agrobacterium tumefaciens-mediated transformation. While no alterations were observed in the pattern and quantity of cell wall-bound phenolic compounds in transgenic plants, the soluble fraction contained several new compounds. The major one was isolated and identified as tyrosol glucoside by liquid chromatography–electrospray ionization–high resolution mass spectrometry and NMR analyses. Our results indicate that expression of a tyrosine decarboxylase in potato does not channel tyramine into the hydroxycinnamoyl-CoA:tyramine N-(hydroxycinnamoyl)-transferase reaction but rather unexpectedly, into a different pathway leading to the formation of a potential storage compound.Expression of a parsley tyrosine decarboxylase in potato unexpectedly channels tyramine into a pathway leading to the formation of tyrosol glucoside.
Publikation
Brunner, F.; Wirtz, W.; Rose, J. K. C.; Darvill, A. G.; Govers, F.; Scheel, D.; Nürnberger, T.;A β-glucosidase/xylosidase from the phytopathogenic oomycete, Phytophthora infestansPhytochemistry59689-696(2002)DOI: 10.1016/S0031-9422(02)00045-6
An 85-kDa β-glucosidase/xylosidase (BGX1) was purified from the axenically grown phytopathogenic oomycete, Phytophthora infestans. The bgx1 gene encodes a predicted 61-kDa protein product which, upon removal of a 21 amino acid leader peptide, accumulates in the apoplastic space. Extensive N-mannosylation accounts for part of the observed molecular mass difference. BGX1 belongs to family 30 of the glycoside hydrolases and is the first such oomycete enzyme deposited in public databases. The bgx1 gene was found in various Phytophthora species, but is apparently absent in species of the related genus, Pythium. Despite significant sequence similarity to human and murine lysosomal glucosylceramidases, BGX1 demonstrated neither glucocerebroside nor galactocerebroside-hydrolyzing activity. The native enzyme exhibited glucohydrolytic activity towards 4-methylumbelliferyl (4-MU) β-d-glucopyranoside and, to lesser extent, towards 4-MU-d-xylopyranoside, but not towards 4-MU-β-d-glucopyranoside. BGX1 did not hydrolyze carboxymethyl cellulose, cellotetraose, chitosan or xylan, suggesting high substrate specificity and/or specific cofactor requirements for enzymatic activity.A β-glucosidase/xylosidase was purified from the phytopathogenic oomycete, Phytophthora infestans. The encoding gene is the first such sequence reported from a species of the kingdom chromista.