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…
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Fellenberg, C.; van Ohlen, M.; Handrick, V.; Vogt, T.;The role of CCoAOMT1 and COMT1 in Arabidopsis anthersPlanta23651-61(2012)DOI: 10.1007/s00425-011-1586-6
Arabidopsis caffeoyl coenzyme A dependent O-methyltransferase 1 (CCoAOMT1) and caffeic acid O-methyltransferase 1 (COMT1) display a similar substrate profile although with distinct substrate preferences and are considered the key methyltransferases (OMTs) in the biosynthesis of lignin monomers, coniferyl and sinapoylalcohol. Whereas CCoAOMT1 displays a strong preference for caffeoyl coenzyme A, COMT1 preferentially methylates 5-hydroxyferuloyl CoA derivatives and also performs methylation of flavonols with vicinal aromatic dihydroxy groups, such as quercetin. Based on different knockout lines, phenolic profiling, and immunohistochemistry, we present evidence that both enzymes fulfil distinct, yet different tasks in Arabidopsis anthers. CCoAOMT1 besides its role in vascular tissues can be localized to the tapetum of young stamens, contributing to the biosynthesis of spermidine phenylpropanoid conjugates. COMT1, although present in the same organ, is not localized in the tapetum, but in two directly adjacent cells layers, the endothecium and the epidermal layer of stamens. In vivo localization and phenolic profiling of comt1 plants provide evidence that COMT1 neither contributes to the accumulation of spermidine phenylpropanoid conjugates nor to the flavonol glycoside pattern of pollen grains.
Publikation
Bektas, I.; Fellenberg, C.; Paulsen, H.;Water-soluble chlorophyll protein (WSCP) of Arabidopsis is expressed in the gynoecium and developing siliquePlanta236251-259(2012)DOI: 10.1007/s00425-012-1609-y
Water-soluble chlorophyll protein (WSCP) has been found in many Brassicaceae, most often in leaves. In many cases, its expression is stress-induced, therefore, it is thought to be involved in some stress response. In this work, recombinant WSCP from Arabidopsis thaliana (AtWSCP) is found to form chlorophyll-protein complexes in vitro that share many properties with recombinant or native WSCP from Brassica oleracea, BoWSCP, including an unusual heat resistance up to 100°C in aqueous solution. A polyclonal antibody raised against the recombinant apoprotein is used to identify plant tissues expressing AtWSCP. The only plant organs containing significant amounts of AtWSCP are the gynoecium in open flowers and the septum of developing siliques, specifically the transmission tract. In fully grown but still green siliques, the protein has almost disappeared. Possible implications for AtWSCP functions are discussed.
Publikation
Weichert, H.; Kolbe, A.; Kraus, A.; Wasternack, C.; Feussner, I.;Metabolic profiling of oxylipins in germinating cucumber seedlings - lipoxygenase-dependent degradation of triacylglycerols and biosynthesis of volatile aldehydesPlanta215612-619(2002)DOI: 10.1007/s00425-002-0779-4
A particular isoform of lipoxygenase (LOX) localized on lipid bodies was shown by earlier investigations to play a role in initiating the mobilization of triacylglycerols during seed germination. Here, further physiological functions of LOXs within whole cotyledons of cucumber (Cucumis sativus L.) were analyzed by measuring the endogenous amounts of LOX-derived products. The lipid-body LOX-derived esterified (13S)-hydroperoxy linoleic acid was the dominant metabolite of the LOX pathway in this tissue. It accumulated to about 14 µmol/g fresh weight, which represented about 6% of the total amount of linoleic acid in cotyledons. This LOX product was not only reduced to its hydroxy derivative, leading to degradation by β-oxidation, but alternatively it was metabolized by fatty acid hydroperoxide lyase leading to formation of hexanal as well. Furthermore, the activities of LOX forms metabolizing linolenic acid were detected by measuring the accumulation of volatile aldehydes and the allene oxide synthase-derived metabolite jasmonic acid. The first evidence is presented for an involvement of a lipid-body LOX form in the production of volatile aldehydes.
Publikation
Vogt, T.;Substrate specificity and sequence analysis define a polyphyletic origin of betanidin 5- and 6-O-glucosyltransferase from Dorotheanthus bellidiformisPlanta214492-495(2002)DOI: 10.1007/s00425-001-0685-1
Betanidin 6-O-glucosyltransferase (6-GT) is involved in the glycosylation of betacyanins, which replace the chromogenic anthocyanins as flower colorants in the Caryophyllales. The 6-GT cDNA was cloned from a cDNA library of Dorotheanthus bellidiformis (Burm. f.) N.E. Br., and the amino acid and nucleotide sequences were shown to be distinctly different from the corresponding betanidin 5-O-glucosyltransferase (5-GT) from the same plant species. Although both enzymes share very similar substrates, the proteins show only 19% amino acid sequence identity. In contrast, the protein sequence of the 6-GT showed significant identity to GTs from other species and may identify a new cluster of putative anthocyanidin GTs. Therefore, 6-GT and 5-GT apparently have evolved independently from ancestral glucosyltransferases involved in flavonoid biosynthesis.