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Publikationen - Molekulare Signalverarbeitung

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Publikation

Calderón Villalobos, L. I. A.; Lee, S.; De Oliveira, C.; Ivetac, A.; Brandt, W.; Armitage, L.; Sheard, L. B.; Tan, X.; Parry, G.; Mao, H.; Zheng, N.; Napier, R.; Kepinski, S.; Estelle, M.; A combinatorial TIR1/AFB–Aux/IAA co-receptor system for differential sensing of auxin Nat. Chem. Biol. 8, 477-485, (2012) DOI: 10.1038/nchembio.926

The plant hormone auxin regulates virtually every aspect of plant growth and development. Auxin acts by binding the F-box protein transport inhibitor response 1 (TIR1) and promotes the degradation of the AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) transcriptional repressors. Here we show that efficient auxin binding requires assembly of an auxin co-receptor complex consisting of TIR1 and an Aux/IAA protein. Heterologous experiments in yeast and quantitative IAA binding assays using purified proteins showed that different combinations of TIR1 and Aux/IAA proteins form co-receptor complexes with a wide range of auxin-binding affinities. Auxin affinity seems to be largely determined by the Aux/IAA. As there are 6 TIR1/AUXIN SIGNALING F-BOX proteins (AFBs) and 29 Aux/IAA proteins in Arabidopsis thaliana, combinatorial interactions may result in many co-receptors with distinct auxin-sensing properties. We also demonstrate that the AFB5–Aux/IAA co-receptor selectively binds the auxinic herbicide picloram. This co-receptor system broadens the effective concentration range of the hormone and may contribute to the complexity of auxin response.
Publikation

Fellenberg, C.; Ziegler, J.; Handrick, V.; Vogt, T.; Polyamine homeostasis in wild type and phenolamide deficient Arabidopsis thaliana stamens Front. Plant Sci. 3, 180, (2012) DOI: 10.3389/fpls.2012.00180

Polyamines (PAs) like putrescine, spermidine, and spermine are ubiquitous polycationic molecules that occur in all living cells and have a role in a wide variety of biological processes. High amounts of spermidine conjugated to hydroxycinnamic acids are detected in the tryphine of Arabidopsis thaliana pollen grains. Tapetum localized spermidine hydroxycinnamic acid transferase (SHT) is essential for the biosynthesis of these anther specific tris-conjugated spermidine derivatives. Sht knockout lines show a strong reduction of hydroxycinnamic acid amides (HCAAs). The effect of HCAA-deficient anthers on the level of free PAs was measured by a new sensitive and reproducible method using 9-fluorenylmethyl chloroformate (FMOC) and fluorescence detection by HPLC. PA concentrations can be accurately determined even when very limited amounts of plant material, as in the case of A. thaliana stamens, are available. Analysis of free PAs in wild type stamens compared to sht deficient mutants and transcript levels of key PA biosynthetic genes revealed a highly controlled regulation of PA homeostasis in A. thaliana anthers.
Bücher und Buchkapitel

Vaira, A. M.; Gago-Zachert, S.; Garcia, M. L.; Guerri, J.; Hammond, J.; Milne, R. G.; Moreno, P.; Morikawa, T.; Natsuaki, T.; Navarro, J. A.; Pallas, V.; Torok, V.; Verbeek, M.; Vetten, H. J.; Family - Ophioviridae (King, A. M. Q., et al., eds.). 743-748, (2012) DOI: 10.1016/B978-0-12-384684-6.00060-4

This chapter focuses on Ophioviridae family whose sole member genus is Ophiovirus. The member species of the genus include Citrus psorosis virus (CPsV), Freesia sneak virus(FreSV), Lettuce ring necrosis virus (LRNV), and Mirafiori lettuce big-vein virus (MiLBVV).The single stranded negative/possibly ambisense RNA genome is divided into 3–4 segments, each of which is encapsidated in a single coat protein (43–50 kDa) forming filamentous virions of about 3 nm in diameter, in shape of kinked or probably internally coiled circles of at least two different contour lengths. Ophioviruses can be mechanically transmitted to a limited range of test plants, inducing local lesions and systemic mottle. The natural hosts of CPsV, ranunculus white mottle virus (RWMV), MiLBVV, and LRNV are dicotyledonous plants of widely differing taxonomy. CPsV has a wide geographical distribution in citrus in the Americas, in the Mediterranean and in New Zealand. FreSV has been reported in two species of the family Ranunculacae from Northern Italy, and in lettuce in France and Germany. Tulip mild mottle mosaic virus (TMMMV) has been reported in tulips in Japan. LRNV is closely associated with lettuce ring necrosis disease in The Netherlands, Belgium, and France, and FreSV has been reported in Europe, Africa, North America and New Zealand.
Publikation

Köck, M.; Groß, N.; Stenzel, I.; Hause, G.; Phloem-specific expression of the wound-inducible ribonuclease LE from tomato (Lycopersicon esculentum cv. Lukullus) Planta 219, 233-242, (2004) DOI: 10.1007/s00425-004-1227-4

Ribonuclease LE (RNaseLE) from tomato (Lycopersicon esculentum Mill. cv. Lukullus) belongs to the widespread RNase T2 family of ribonucleases. With the exception of S-RNases of the solanaceous self-incompatibility system the functions of other members of the RNase T2 family are only barely understood. Using a 2.6-kbp putative promoter sequence of RNaseLE in front of the uidA reporter gene, expression of β-glucuronidase in developing phloem tissue and, especially, in the meristematic and elongation zones at root tips was detected. The tissue-specific expression accords with the range of cis-acting elements detected in the RNaseLE promoter. RNaseLE mRNA was localized in developing phloem cells but not in mature phloem tissue, suggesting association of RNaseLE expression with phloem development. Histochemical staining of β-glucuronidase activity as well as detailed inspection of RNaseLE at mRNA, protein and enzyme activity levels revealed that the wound-induced expression of RNaseLE was also restricted to vascular tissue. RNaseLE transcript accumulation detected by in situ hybridization occurred preferentially in phloem and cambial cells of stem sections upon wounding. The data provide evidence for a role of RNaseLE in a tissue-specific wound response and in wound healing of tomato.
Publikation

Groß, N.; Wasternack, C.; Köck, M.; Wound-induced RNaseLE expression is jasmonate and systemin independent and occurs only locally in tomato (Lycopersicon esculentum cv. Lukullus) Phytochemistry 65, 1343-1350, (2004) DOI: 10.1016/j.phytochem.2004.04.036

Tomato RNaseLE is induced by phosphate deficiency and wounding and may play a role in macromolecular recycling as well as wound healing. Here, we analyzed the role of jasmonate and systemin in the wound-induced RNaseLE activation. The rapid expression of RNaseLE upon wounding of leaves leading to maximal RNase activity within 10 h, appeared only locally. Jasmonic acid (JA) or its molecular mimic ethyl indanoyl isoleucine conjugate did not induce RNaseLE expression. Correspondingly, RNaseLE was expressed upon wounding of 35S::allene oxide cyclase antisense plants known to be JA deficient. RNaseLE was not expressed upon systemin treatment, but was locally expressed in the spr1 mutant which is affected in systemin perception. In tomato plants carrying a PromLE::uidA construct, GUS activity could be detected upon wounding, but not following treatment with JA or systemin. The data indicate a locally acting wound-inducible systemin- and JA-independent signaling pathway for RNaseLE expression.RNaseLE expression was analyzed by pharmacological studies of different tomato lines and upon wounding of leaves. The gene is only locally activated via a new type of wound-induced signaling pathway in a jasmonate/systemin-independent manner.
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