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Publikationen - Molekulare Signalverarbeitung

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Publikation

Abel, S. Auxin is surfacing ACS Chemical Biology 2, 380 - 384, (2007)

Indole-3-acetic acid (IAA or auxin) is essential throughout the life cycle of a plant. It controls diverse cellular processes, including gene expression. The hormone is perceived by a ubiquitin protein ligase (E3) and triggers the rapid destruction of repressors, called Aux/IAA proteins. The first structural model of a plant hormone receptor illustrates how auxin promotes Aux/IAA substrate recruitment by extending the hydrophobic protein-interaction surface. This work establishes a novel mechanism of E3 regulation by small molecules and promises a novel strategy for the treatment of human disorders associated with defective ubiquitin-dependent proteolysis.

Publikation

Tan, X., Calderón Villalobos, L.I., Sharon, M., Zheng, C., Robinson, C.V., Estelle, M. & Zheng, N. Mechanism of auxin perception by the TIR1 ubiquitin ligase Nature 446(7136), 640-645, (2007)

Arabidopsis

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

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

Wasternack, C. Jasmonates: An update on biosynthesis, signal transduction and action in plant stress response, growth and development Annals of Botany 100, 681-697, (2007)

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Publikation

Delker, C., Zolman, B.K., Miersch, O. & Wasternack, C. Jasmonate biosynthesis in Arabidopsis thaliana requires peroxisomal beta-oxidation enzymes Additional proof by properties of pex6 and aim1 Phytochemistry 68, 1642-1650, (2007)

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Publikation

Schilling, S., Stenzel, I., von Bohlen, A., Wermann, M., Schulz, K., Demuth, H.-U. & Wasternack, C. Isolation and characterization of the glutaminyl cyclases from Solanum tuberosum and Arabidopsis thaliana: implications for physiological functions Biol. Chem 388, 145-153, (2007)

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Publikation

Vigliocco, A., Alemano, S., Miersch, O., Alvarez, D. & Abdala, G. Endogenous jasmonates in dry and imbibed sunflower seeds from plants grown at different soil moisture contents Seed Sci. Res. 17, 91-98, (2007)

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Publikation

Flores, R., Navarro, B., Gago, S. & de la Peña, M. Chrysanthemum Chlorotic Mottle Viroid: a System for Reverse Genetics in the Family Avsunviroidae (Hammerhead Viroids) Plant Viruses 1, 27-32, (2007)

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Publikation

Pedranzani, H., Sierro-de-Grado, R., Vigliocco, A., Miersch, O. & Abdala, G. Cold and water stresses produce changes in endogenous jasmonates in two populations of Pinus pinaster Ait Plant Growth Regul. 52, 111-116, (2007)

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Publikation

Biondi, E., Branciamore, S., Fusi, L., Gago, S. & Gallori, E. Catalytic activity of hammerhead ribozymes in a clay mineral environment: Implications for the RNA world. Gene 389, 10-18, (2007)

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Publikation

Schwager, K.M., Calderón Villalobos, L.I., Dohmann, E.M., Willige, B.C., Knierer, S., Nill, C. & Schwechheimer, C. Characterization of the VIER F-BOX PROTEINE genes from Arabidopsis reveals their importance for plant growth and development Plant Cell 19(4), 1163-1178, (2007)

E3 ubiquitin ligases (E3s) target proteins for degradation by the 26S proteasome. In SKP1/CDC53/F-box proteintype E3s, substrate specificity is conferred by the interchangeable F-box protein subunit. The vast majority of the 694 F-box proteins encoded by the Arabidopsis thaliana genome remain to be understood. We characterize the VIER F-BOX PROTEINE (VFB; German for FOUR F-BOX PROTEINS) genes from Arabidopsis that belong to subfamily C of the Arabidopsis F-box protein superfamily. This subfamily also includes the F-box proteins TRANSPORT INHIBITOR RESPONSE1 (TIR1)/AUXIN SIGNALING F-BOX (AFB) proteins and EIN3 BINDING F-BOX proteins, which regulate auxin and ethylene responses, respectively. We show that loss of VFB function causes delayed plant growth and reduced lateral root formation. We find that the expression of a number of auxin-responsive genes and the activity of DR5:ß-glucuronidase, a reporter for auxin reponse, are reduced in the vfb mutants. This finding correlates with an increase in the abundance of an AUXIN/INDOLE-3-ACETIC ACID repressor. However, we also find that auxin responses are not affected in the vfb mutants and that a representative VFB family member, VFB2, cannot functionally complement the tir1-1 mutant. We therefore exclude the possibility that VFBs are functional orthologs of TIR1/AFB proteins.

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