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…
Lukačin, R.; Matern, U.; Specker, S.; Vogt, T.;Cations modulate the substrate specificity of bifunctional class I O-methyltransferase from Ammi majusFEBS Lett.577367-370(2004)DOI: 10.1016/j.febslet.2004.10.032
Caffeoyl‐coenzyme A O‐methyltransferase cDNA was cloned from dark‐grown Ammi majus L. (Apiaceae) cells treated with a crude fungal elicitor and the open reading frame was expressed in Escherichia coli . The translated polypeptide of 27.1‐kDa shared significant identity to other members of this highly conserved class of proteins and was 98.8% identical to the corresponding O‐methyltransferase from parsley. For biochemical characterization, the recombinant enzyme could be purified to apparent homogeneity by metal‐affinity chromatography, although the recombinant enzyme did not contain any affinity tag. Based on sequence analysis and substrate specificity, the enzyme classifies as a cation‐dependent O‐methyltransferase with pronounced preference for caffeoyl coenzyme A, when assayed in the presence of Mg2+‐ions. Surprisingly, however, the substrate specificity changed dramatically, when Mg2+ was replaced by Mn2+ or Co2+ in the assays. This effect could point to yet unknown functions and substrate specificities in situ and suggests promiscuous roles for the lignin specific cluster of plant O‐methyltransferases.
Publikation
Flores, R.; Delgado, S.; Gas, M.-E.; Carbonell, A.; Molina, D.; Gago, S.; De la Peña, M.;Viroids: the minimal non-coding RNAs with autonomous replicationFEBS Lett.56742-48(2004)DOI: 10.1016/j.febslet.2004.03.118
Viroids are small (246–401 nucleotides), non‐coding, circular RNAs able to replicate autonomously in certain plants. Viroids are classified into the families Pospiviroidae and Avsunviroidae , whose members replicate in the nucleus and chloroplast, respectively. Replication occurs by an RNA‐based rolling‐circle mechanism in three steps: (1) synthesis of longer‐than‐unit strands catalyzed by host DNA‐dependent RNA polymerases forced to transcribe RNA templates, (2) processing to unit‐length, which in family Avsunviroidae is mediated by hammerhead ribozymes, and (3) circularization either through an RNA ligase or autocatalytically. Disease induction might result from the accumulation of viroid‐specific small interfering RNAs that, via RNA silencing, could interfere with normal developmental pathways.
Publikation
Bücking, H.; Förster, H.; Stenzel, I.; Miersch, O.; Hause, B.;Applied jasmonates accumulate extracellularly in tomato, but intracellularly in barleyFEBS Lett.56245-50(2004)DOI: 10.1016/S0014-5793(04)00178-4
Jasmonic acid (JA) and its derivatives are well‐characterized signaling molecules in plant defense and development, but the site of their localization within plant tissue is entirely unknown. To address the question whether applied JA accumulates extracellularly or intracellularly, leaves of tomato and barley were fed with 14C‐labeled JA and the label was localized in cryofixed and lyophilized leaf tissues by microautoradiography. In tomato the radioactivity was detectable within the apoplast, but no label was found within the mesophyll cells. By contrast, in barley leaf tissues, radioactivity was detected within the mesophyll cells suggesting a cellular uptake of exogenously applied JA. JA, applied to leaves of both plants as in the labeling experiments, led in all leaf cells to the expression of JA‐inducible genes indicating that the perception is completed by JA signal transduction.
In elicitor-treated potato cells, 9-lipoxygenase-derived oxylipins accumulate with the divinyl ether colneleic acid as the major metabolite. Here, the identification of a potato cDNA is described, whose predicted amino acid sequence corresponds to divinyl ether synthases, belonging to the recently identified new P450 subfamily CYP74D. The recombinant protein was expressed in Escherichia coli and shown to metabolize 9-hydroperoxy linoleic acid to colneleic acid at pH 6.5. This fatty acid derivative has been implicated in functioning as a plant antimicrobial compound. RNA blot analyses revealed accumulation of divinyl ether synthase transcripts both upon infiltration of potato leaves with Pseudomonas syringae and after infection with Phytophthora infestans.