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Publikation

Hamdi, I.; Elleuch, A.; Bessaies, N.; Grubb, C. D.; Fakhfakh, H. First report of Citrus viroid V in North Africa J Gen Plant Pathol 81, 87-91, (2015) DOI: 10.1007/s10327-014-0556-9

We tested citrus samples from Tunisia using reverse transcription-polymerase chain reaction (RT-PCR), and for the first time, Citrus viroid V (CVd-V) was reported in North Africa. Fourteen of 38 tested citrus trees were infected by CVd-V including the majority of varieties grown in Tunisia. Some RT-PCR results were also supported by biological indexing. After sequencing the RT-PCR products, three new CVd-V variants were identified, showing 80–91 % nucleotide sequence identity with those reported previously. Based on phylogenetic analysis using all CVd-V sequences in GenBank, two main CVd-V groups were identified. Furthermore, construction of a genetic network of the detected haplotypes using the same sequences shows a clear geographical structuring of Tunisian CVd-V variants.
Publikation

Erickson, J. l.; Ziegler, J.; Guevara, D.; Abel, S.; Klösgen, R. B.; Mathur, J.; Rothstein, S. J.; Schattat, M.H. Agrobacterium-derived cytokinin influences plastid morphology and starch accumulation inNicotiana benthamiana during transient assays BMC Plant Biol. 14, 127, (2014) DOI: 10.1186/1471-2229-14-127

Background: Agrobacterium tumefaciens-based transient assays have become a common tool for answering questions related to protein localization and gene expression in a cellular context. The use of these assays assumes that the transiently transformed cells are observed under relatively authentic physiological conditions and maintain ‘normal’ sub-cellular behaviour. Although this premise is widely accepted, the question of whether cellular organization andorganelle morphology is altered in Agrobacterium-infiltrated cells has not been examined in detail. The first indications of an altered sub-cellular environment came from our observation that a common laboratory strain, GV3101(pMP90), caused a drastic increase in stromule frequency. Stromules, or ‘stroma-filled-tubules’ emanate fromthe surface of plastids and are sensitive to a variety of biotic and abiotic stresses. Starting from this observation, the goal of our experiments was to further characterize the changes to the cell resulting from short-term bacterial infestation, and to identify the factor responsible for eliciting these changes.Results: Using a protocol typical of transient assays we evaluated the impact of GV3101(pMP90) infiltration on chloroplast behaviour and morphology in Nicotiana benthamiana. Our experiments confirmed that GV3101(pMP90) consistently induces stromules and alters plastid position relative to the nucleus. These effects were found to be the result of strain-dependant secretion of cytokinin and its accumulation in the plant tissue. Bacterial production of the hormone was found to be dependant on the presence of a trans-zeatin synthase gene (tzs) located on the Ti plasmidof GV3101(pMP90). Bacteria-derived cytokinins were also correlated with changes to both soluble sugar level and starch accumulation.Conclusion: Although we have chosen to focus on how transient Agrobacterium infestation alters plastid based parameters, these changes to the morphology and position of a single organelle, combined with the measured increases in sugar and starch content, suggest global changes to cell physiology. This indicates that cells visualized during transient assays may not be as ‘normal’ as was previously assumed. Our results suggest that the impact of the bacteria can be minimized by choosing Agrobacterium strains devoid of the tzs gene, but that the alterations to sub-cellular organization and cell carbohydrate status cannot be completely avoided using this strategy.Keywords: Agrobacterium tumefaciens, Nicotiana benthamiana, Transient assays, GV3101(pMP90), LBA4404, Plastid,Stromules, Bacteria-derived, Cytokinin, Trans-zeatin synthase
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) DOI: 10.1515/BC.2007.016

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Publikation

Guranowski, A.; Miersch, O.; Staswick, P.E.; Suza, W.; Wasternack, C. Substrate specificity and products of side-reactions catalyzed by jasmonate:amino acid synthetase (JAR1) FEBS Letters 581, 815-820, (2007) DOI: 10.1016/j.febslet.2007.01.049

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Publikation

Flores, R.; Delgado, S.; Gas, M.E.; Carbonell, A.; Molina, D.; Gago, S.; de la Peña, M. Viroids: the minimal non-coding RNA's with autonomous replication FEBS Letters 567, 42-48, (2004) DOI: 10.1016/j.febslet.2004.03.118

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Publikation

Vigliocco, A.; Bonamico, M.B.; Alemano, S.; Miersch, O.; Abdala, G. Activation of jasmonic acid production in <EM>Zea mays</EM> L. infected by the maize rough dwarf virus-Río Cuarto. Reversion of symptoms by salicylic acid Biocell 26(3), 369-374, (2002)

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Publikation

Morgan, K.E.; Zarembinski, T.I.; Theologis, A.; Abel, S. Biochemical characterization of recombinant polypeptides corresponding to the predicted ßαα-fold in Aux/IAA proteins FEBS Letters 454, 283-287, (1999)

The plant hormone indoleacetic acid (IAA or auxin) transcriptionally activates a select set of early genes. The Auxl IAA class of early auxin-responsive genes encodes a large family of short-lived, nuclear proteins. Aux/IAA polypeptides homo-and heterodimerize, and interact with auxin-response transcription factors (ARFs) via C-terminal regions conserved in both protein families. This shared region contains a predicted βαα motif similar to the prokaryotic β-Ribbon DNA binding domain, which mediates both protein dimerization and DNA recognition. Here, we show by circular dichroism spectroscopy and by chemical cross-linking experiments that recombinant peptides corresponding to the predicted βαα region of three Aux/IAA proteins from Arabidopsis thaliana contain substantial α-helical secondary structure and undergo homo- and heterotypic interactions in vitro. Our results indicate a similar biochemical function of the plant βαα domain and suggest that the βαα fold plays an important role in mediating combinatorial interactions of Aux/IAA and ARF proteins to specifically regulate secondary gene expression in response to auxin.
Publikation

Bohlmann, H.; Vignutelli, A.; Hilpert, B.; Miersch, O.; Wasternack, C.; Apel, K. Wounding and chemicals induce expression of the Arabidopsis gene Thi2.1, encoding a fungal defense thionin, via the octadecanoid pathway FEBS Letters 437, 281-286, (1998)

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Publikation

Hertel, S.; Knöfel, H.-D.; Kramell, R.; Miersch, O. Partial purification and characterization of a jasmonic acid conjugate cleaving amidohydrolase from the fungus <EM>Botryodiplodia theobromae</EM> FEBS Letters 407, 105-110, (1997)

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Publikation

Görschen, E.; Dunaeva, M.; Reeh, I.; Wasternack, C. Overexpression of the jasmonate inducible 23 kDa protein (JIP 23) from barley in transgenic tobacco leads to the repression of leaf proteins FEBS Letters 419, 58-62, (1997)

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