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…
Müller, H.; Heinze, M.; Heinke, R.; Schmidt, J.; Roos, W.;Self-regulation of phytoalexin production: a non-biosynthetic enzyme controls alkaloid biosynthesis in cultured cells of Eschscholzia californicaPlant Cell Tiss. Organ Cult.119661-676(2014)DOI: 10.1007/s11240-014-0565-6
Benzophenanthridine alkaloids are strong antimicrobials of Papaveraceae and attractive lead compounds for drug development. The cytotoxicity of these compounds requires the producing plant to limit the pathogen-triggered burst of biosynthesis. Cells of Eschscholzia californica excrete early benzophenanthridines to the cell wall, followed by re-uptake and reduction in the cytoplasm by the detoxifying enzyme sanguinarine reductase. We now discovered that this enzyme is a core component of self-control in alkaloid production. RNAi-based silencing of sanguinarine reductase gave rise to mutants that either show a complete stop of elicitor-triggered alkaloid production or a burst of biosynthesis that severalfold surpasses the wild type level. These unexpected phenotypes reflect impacts of substrate or product of sanguinarine reductase: the substrate, sanguinarine, inhibits phospholipase A2 at the plasma membrane, an initial component of the signal path towards expression of biosynthetic enzymes. The product, dihydrosanguinarine, inhibits enzymes of early biosynthesis, prior to reticuline formation. By tuning these steady states, sanguinarine reductase adjusts the capacity of alkaloid biosynthesis: a minimum activity is sufficient to prevent the blockade of the induction pathway by sanguinarine, while the full activity of the same enzyme causes a limitation of the biosynthetic flow via dihydrosanguinarine.
Publikation
Schrick, K.; Mayer, U.; Horrichs, A.; Kuhnt, C.; Bellini, C.; Dangl, J.; Schmidt, J.; Jürgens, G.;FACKEL is a sterol C-14 reductase required for organized cell division and expansion in Arabidopsis embryogenesisGenes Dev.141471-1484(2000)DOI: 10.1101/gad.14.12.1471
In flowering plants, the developing embryo consists of growing populations of cells whose fates are determined in a position-dependent manner to form the adult organism. Mutations in the FACKEL(FK) gene affect body organization of theArabidopsis seedling. We report that FK is required for cell division and expansion and is involved in proper organization of the embryo. We isolated FK by positional cloning. Expression analysis in embryos revealed that FK mRNA becomes localized to meristematic zones. FK encodes a predicted integral membrane protein related to the vertebrate lamin B receptor and sterol reductases across species, including yeast sterol C-14 reductase ERG24. We provide functional evidence that FK encodes a sterol C-14 reductase by complementation of erg24. GC/MS analysis confirmed that fk mutations lead to accumulation of intermediates in the biosynthetic pathway preceding the C-14 reductase step. Although fk represents a sterol biosynthetic mutant, the phenotype was not rescued by feeding with brassinosteroids (BRs), the only plant sterol signaling molecules known so far. We propose that synthesis of sterol signals in addition to BRs is important in mediating regulated cell growth and organization during embryonic development. Our results indicate a novel role for sterols in the embryogenesis of plants.