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…
Tan, X.; Calderon-Villalobos, L. I. A.; Sharon, M.; Zheng, C.; Robinson, C. V.; Estelle, M.; Zheng, N.;Mechanism of auxin perception by the TIR1 ubiquitin ligaseNature446640-645(2007)DOI: 10.1038/nature05731
Auxin is a pivotal plant hormone that controls many aspects of plant growth and development. Perceived by a small family of F-box proteins including transport inhibitor response 1 (TIR1), auxin regulates gene expression by promoting SCF ubiquitin-ligase-catalysed degradation of the Aux/IAA transcription repressors, but how the TIR1 F-box protein senses and becomes activated by auxin remains unclear. Here we present the crystal structures of the Arabidopsis TIR1–ASK1 complex, free and in complexes with three different auxin compounds and an Aux/IAA substrate peptide. These structures show that the leucine-rich repeat domain of TIR1 contains an unexpected inositol hexakisphosphate co-factor and recognizes auxin and the Aux/IAA polypeptide substrate through a single surface pocket. Anchored to the base of the TIR1 pocket, auxin binds to a partially promiscuous site, which can also accommodate various auxin analogues. Docked on top of auxin, the Aux/IAA substrate peptide occupies the rest of the TIR1 pocket and completely encloses the hormone-binding site. By filling in a hydrophobic cavity at the protein interface, auxin enhances the TIR1–substrate interactions by acting as a ‘molecular glue’. Our results establish the first structural model of a plant hormone receptor.
Publikation
Nualkaew, N.; Guennewich, N.; Springob, K.; De-Eknamkul, W.; Zenk, M.; Kutchan, T.;cDNA cloning of prenyl diphosphate phosphatase from Croton stellatopilosus OhbaPlanta Med.73P_636(2007)DOI: 10.1055/s-2007-987416
Geranylgeraniol (GGOH) is an acyclic diterpene that posesses apoptotic activity to cancer cells [1]. It has been proposed to be the main intermediate of the biosynthetic pathway of plaunotol, an antipeptic ulcer drug from Croton stellatopilosus [2]. Our enzymological studies showed that GGOH is formed from the dephosphorylation of geranylgeranyl pyrophosphate (GGPP), through sequential monodephosphorylation [3], by the action of GGPP phosphatase enzyme [4]. As part of our interest in manipulating the gene of GGPP phosphatase for the production of GGOH in Escherichia coli system, we began with cloning of cDNA encoding prenyl diphosphate phosphatase from C. stellatopilosus. The degenerated primers were designed from the alignment of amino acid sequences of prenyl diphosphate phosphatase in database. The full-length gene was obtained by RACE-PCR. The cDNA contained an open reading frame encoding 888 amino acids with a calculated molecular mass of 33.6 kDa. The phosphatase motif [5] was included in the deduced amino acid sequence consisting of KX6RP, PSGH, and SRX5HX3D. Its amino acid sequence showed 71% identity to phosphatidic acid phosphatase from Vigna unguiculata. The topology prediction of the enzyme indicated that it was a transmembrane protein with 6 transmembrane regions. The recombinant prenyl diphosphate phosphatase and its 4 designed truncated genes were expressed in Escherichia coli BL21(DE3)RIL. Detection of their phosphatase activities by using [1-3H]GGPP and farnesyl pyrophosphate ([1-3H]FPP) as substrates showed that their enzymatic products of [1-3H]GGOH and [1-3H]FOH, respectively, were formed in the assay mixture. The results suggested the potential of GGOH production by the recombinant E. coli although the expression of the recombinant gene was still in low level.
In developing progeny of mammals the two parental genomes are differentially expressed according to imprinting marks, and embryos with only a uniparental genetic contribution die1,2,3. Gene expression that is dependent on the parent of origin has also been observed in the offspring of flowering plants, and mutations in the imprinting machinery lead to embryonic lethality, primarily affecting the development of the endosperm—a structure in the seed that nourishes the embryo, analogous to the function of the mammalian placenta4. Here we have generated Arabidopsis thaliana seeds in which the endosperm is of uniparental, that is, maternal, origin. We demonstrate that imprinting in developing seeds can be bypassed and viable albeit smaller seedlings can develop from seeds lacking a paternal contribution to the endosperm. Bypassing is only possible if the mother is mutant for any of the FIS-class genes, which encode Polycomb group chromatin-modifying factors. Thus, these data provide functional evidence that the action of the FIS complex balances the contribution of the paternal genome. As flowering plants have evolved a special reproduction system with a parallel fusion of two female with two male gametes, our findings support the hypothesis that only with the evolution of double fertilization did the action of the FIS genes become a requirement for seed development. Furthermore, our data argue for a gametophytic origin of endosperm in flowering plants, thereby supporting a hypothesis raised in 1900 by Eduard Strasburger.
Publikation
Namjooyan, F.; Azemi, M.; Mosaddegh, M.; Cheraghali, A.; Kobarfard, F.; Porzel, A.;Screening of some Solanaceae plants for cytotoxic activity, and isolation and structure elucidation of a new steroid from the active fraction of Physalis divarivata D. DonPlanta Med.73P_422(2007)DOI: 10.1055/s-2007-987202