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…
Plant isoprenoids are formed from precursors synthesized by the mevalonate (MVA) pathway in the cytosol or by the methyl-D-erythritol 4-phosphate (MEP) pathway in plastids. Although some exchange of precursors occurs, cytosolic sesquiterpenes are assumed to derive mainly from MVA, while plastidial monoterpenes are produced preferentially from MEP precursors. Additional complexity arises in the first step of the MEP pathway, which is typically catalyzed by two divergent 1-deoxy-D-xylulose 5-phosphate synthase isoforms (DXS1, DXS2). In tomato (Solanum lycopersicum), the SlDXS1 gene is ubiquitously expressed with highest levels during fruit ripening, whereas SlDXS2 transcripts are abundant in only few tissues, including young leaves, petals, and isolated trichomes. Specific down-regulation of SlDXS2 expression was performed by RNA interference in transgenic plants to investigate feedback mechanisms. SlDXS2 down-regulation led to a decrease in the monoterpene β-phellandrene and an increase in two sesquiterpenes in trichomes. Moreover, incorporation of MVA-derived precursors into residual monoterpenes and into sesquiterpenes was elevated as determined by comparison of 13C to 12C natural isotope ratios. A compensatory up-regulation of SlDXS1 was not observed. Down-regulated lines also exhibited increased trichome density and showed less damage by leaf-feeding Spodoptera littoralis caterpillars. The results reveal novel, non-redundant roles of DXS2 in modulating isoprenoid metabolism and a pronounced plasticity in isoprenoid precursor allocation.
The general phenylpropanoid metabolism generates an enormous array of secondary metabolites based on the few intermediates of the shikimate pathway as the core unit. The resulting hydroxycinnamic acids and esters are amplified in several cascades by a combination of reductases, oxygenases, and transferases to result in an organ and developmentally specific pattern of metabolites, characteristic for each plant species. During the last decade, methodology driven targeted and non-targeted approaches in several plant species have enabled the identification of the participating enzymes of this complex biosynthetic machinery, and revealed numerous genes, enzymes, and metabolites essential for regulation and compartmentation. Considerable success in structural and computational biology, combined with the analytical sensitivity to detect even trace compounds and smallest changes in the metabolite, transcript, or enzyme pattern, has facilitated progress towards a comprehensive view of the plant response to its biotic and abiotic environment. Transgenic approaches have been used to reveal insights into an apparently redundant gene and enzyme pattern required for functional integrity and plasticity of the various phenylpropanoid biosynthetic pathways. Nevertheless, the function and impact of all members of a gene family remain to be completely established. This review aims to give an update on the various facets of the general phenylpropanoid pathway, which is not only restricted to common lignin or flavonoid biosynthesis, but feeds into a variety of other aromatic metabolites like coumarins, phenolic volatiles, or hydrolyzable tannins.
Publikation
Feussner, I.; Porzel, A.; Wasternack, C.; Kühn, H.;Quantitative Analyse von Lipoxygenase-Metaboliten in Lipiden durch NMR-SpektroskopieBIOspektrum354-58(1997)