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Publikation

Wasternack, C. Action of jasmonates in plant stress responses and development — Applied aspects Biotechnol Adv 32 , 31-39, (2014) DOI: 10.1016/j.biotechadv.2013.09.009

Jasmonates (JAs) are lipid-derived compounds acting as key signaling compounds in plant stress responses and development. The JA co-receptor complex and several enzymes of JA biosynthesis have been crystallized, and various JA signal transduction pathways including cross-talk to most of the plant hormones have been intensively studied. Defense to herbivores and necrotrophic pathogens are mediated by JA. Other environmental cues mediated by JA are light, seasonal and circadian rhythms, cold stress, desiccation stress, salt stress and UV stress. During development growth inhibition of roots, shoots and leaves occur by JA, whereas seed germination and flower development are partially affected by its precursor 12-oxo-phytodienoic acid (OPDA). Based on these numerous JA mediated signal transduction pathways active in plant stress responses and development, there is an increasing interest in horticultural and biotechnological applications. Intercropping, the mixed growth of two or more crops, mycorrhization of plants, establishment of induced resistance, priming of plants for enhanced insect resistance as well as pre- and post-harvest application of JA are few examples. Additional sources for horticultural improvement, where JAs might be involved, are defense against nematodes, biocontrol by plant growth promoting rhizobacteria, altered composition of rhizosphere bacterial community, sustained balance between growth and defense, and improved plant immunity in intercropping systems. Finally, biotechnological application for JA-induced production of pharmaceuticals and application of JAs as anti-cancer agents were intensively studied.
Publikation

Bosch, M.; Wright, L. P.; Gershenzon, J.; Wasternack, C.; Hause, B.; Schaller, A.; Stintzi, A. Jasmonic acid and its precursor 12-oxophytodienoic acid control different aspects of constitutive and induced herbivore defenses in tomato Plant Physiology 166, 396-410, (2014) DOI: 10.1104/pp.114.237388

The jasmonate family of growth regulators includes the isoleucine conjugate of jasmonic acid (JA-Ile) and its biosynthetic precursor 12-oxophytodienoic acid (OPDA) as signaling molecules. In order to assess the relative contribution of JA/JA-Ile and OPDA to insect resistance in tomato, we silenced the expression of OPDA reductase (OPR3) by RNA interference. Consistent with a block in the biosynthetic pathway downstream of OPDA, OPR3-RNAi plants contained wild-type levels of OPDA but failed to accumulate JA or JA-Ile after wounding. JA/JA-Ile deficiency in OPR3-RNAi plants resulted in reduced trichome formation and impaired monoterpene and sesquiterpene production. The loss of these JA/JA-Ile-dependent defense traits rendered them more attractive to the specialist herbivore Manduca sexta with respect to feeding and oviposition. Oviposition preference resulted from reduced levels of repellant mono- and sesquiterpenes. Feeding preference, on the other hand, was caused by increased production of cis-3-hexenal acting as a feeding stimulant for M. sexta larvae in OPR3-RNAi plants. Despite impaired constitutive defenses and increased palatability of OPR3-RNAi leaves, larval development was indistinguishable on OPR3-RNAi and wild-type plants, and much delayed as compared to development on the JA/JA-Ile insensitive (jai1) mutant. Apparently, signaling through JAI1, the tomato ortholog of COI1 in Arabidopsis, is required for defense while the conversion of OPDA to JA/JA-Ile is not. Comparing the signaling activities of OPDA and JA/JA-Ile, we found that OPDA can substitute for JA/JA-Ile in the local induction of defense gene expression, but the production of JA/JA-Ile is required for a systemic response.
Publikation

Wasternack, C.; Hause, B. Jasmonsäure – ein universelles Pflanzenhormon: Blütenduft, Abwehr, Entwicklung Biologie in unserer Zeit 44, 164 - 171, (2014) DOI: 10.1002/biuz.201410535

Jasmonsäure (JA) und ihre Metaboliten kommen in allen niederen und höheren Pflanzen vor. Sie sind universell wirksame, aus Lipiden gebildete Signalstoffe bei der Abwehr von biotischem und abiotischem Stress sowie in der pflanzlichen Entwicklung. Rezeptor und Komponenten von JA–Signalketten wurden identifiziert. In der Entwicklung von Blüten, Früchten, Samen, Trichomen oder in der Abwehr von Insekten und Pathogenen treten ähnliche JA-vermittelte Signalproteine auf, die eine Feinregulation der Prozesse erlauben und eine Verbindung (cross-talk) zu anderenPflanzenhormonen aufweisen.
Bücher und Buchkapitel

Wasternack, C. Jasmonates in plant growth and stress responses. (Tran, L.-S.; Pal, S.). Springer, 221-264, (2014) ISBN: 978-1-4939-0490-7 (hardcover) 978-1-4939-4814-7 (softcover) DOI: 10.1007/978-1-4939-0491-4_8

Abiotic and biotic stresses adversely affect plant growth and productivity. The phytohormones regulate key physiological events under normal and stressful conditions for plant development. Accumulative research efforts have discovered important roles of phytohormones and their interactions in regulation of plant adaptation to numerous stressors. Intensive molecular studies have elucidated various plant hormonal pathways; each of which consist of many signaling components that link a specific hormone perception to the regulation of downstream genes. Signal transduction pathways of auxin, abscisic acid, cytokinins, gibberellins and ethylene have been thoroughly investigated. More recently, emerging signaling pathways of brassinosteroids, jasmonates, salicylic acid and strigolactones offer an exciting gateway for understanding their multiple roles in plant physiological processes.At the molecular level, phytohormonal crosstalks can be antagonistic or synergistic or additive in actions. Additionally, the signal transduction component(s) of one hormonal pathway may interplay with the signaling component(s) of other hormonal pathway(s). Together these and other research findings have revolutionized the concept of phytohormonal studies in plants. Importantly, genetic engineering now enables plant biologists to manipulate the signaling pathways of plant hormones for development of crop varieties with improved yield and stress tolerance.This book, written by internationally recognized scholars from various countries, represents the state-of-the-art understanding of plant hormones’ biology, signal transduction and implications. Aimed at a wide range of readers, including researchers, students, teachers and many others who have interests in this flourishing research field, every section is concluded with biotechnological strategies to modulate hormone contents or signal transduction pathways and crosstalk that enable us to develop crops in a sustainable manner. Given the important physiological implications of plant hormones in stressful environments, our book is finalized with chapters on phytohormonal crosstalks under abiotic and biotic stresses. 
Bücher und Buchkapitel

Tissier, A.; Ziegler, J.; Vogt T. Specialized plant metabolites: Diversity and biosynthesis  (Krauß, G. J.; Nies, D. H.). 14-37, (2014) ISBN: 978-3-527-31650-2 DOI: 10.1002/9783527686063.ch2

Plant secondary metabolites, also termed specialized plant metabolites, currently comprise more than 200 000 natural products that are all based on a few biosynthetic pathways and key primary metabolites. Some pathways like flavonoid and terpenoid biosynthesis are universally distributed in the plant kingdom, whereas others like alkaloid or cyanogenic glycoside biosynthesis are restricted to a limited set of taxa. Diversification is achieved by an array of mechanisms at the genetic and enzymatic level including gene duplications, substrate promiscuity of enzymes, cell-specific regulatory systems, together with modularity and combinatorial aspects. Specialized metabolites reflect adaptations to a specific environment. The observed diversity illustrates the heterogeneity and multitude of ecological habitats and niches that plants have colonized so far and constitutes a reservoir of potential new metabolites that may provide adaptive advantage in the face of environmental changes. The code that connects the observed chemical diversity to this ecological diversity is largely unknown. One way to apprehend this diversity is to realize its tremendous plasticity and evolutionary potential. This chapter presents an overview of the most widespread and popular secondary metabolites, which provide a definite advantage to adapt to or to colonize a particular environment, making the boundary between the “primary” and the “secondary” old fashioned and blurry.
Publikation

Budiharjo, A.; Chowdhury, S.M.; Dietel, C.; Beator, B.; Dolgova, O.; Fan, B.; Bleiss, W.; Ziegler, J.; Schmid, M.; Hartmann, A.; Borris, R. Transposon Mutagenesis of the Plant-Associated Bacillus amyloliquefaciens ssp. plantarum FZB42 Revealed That the nrfA and RBAM17410 Genes Are Involved in Plant-Microbe-Interactions PLOS ONE 9, e98267, (2014) DOI: 10.1371/journal.pone.0098267

Bacillus amyloliquefaciens ssp. plantarum FZB42 represents the prototype of Gram-positive plant growth promoting and biocontrol bacteria. In this study, we applied transposon mutagenesis to generate a transposon library, which was screened for genes involved in multicellular behavior and biofilm formation on roots as a prerequisite of plant growth promoting activity. Transposon insertion sites were determined by rescue-cloning followed by DNA sequencing. As in B. subtilis, the global transcriptional regulator DegU was identified as an activator of genes necessary for swarming and biofilm formation, and the DegU-mutant of FZB42 was found impaired in efficient root colonization. Direct screening of 3,000 transposon insertion mutants for plant-growth-promotion revealed the gene products of nfrA and RBAM_017140 to be essential for beneficial effects exerted by FZB42 on plants. We analyzed the performance of GFP-labeled wild-type and transposon mutants in the colonization of lettuce roots using confocal laser scanning microscopy. While the wild-type strain heavily colonized root surfaces, the nfrA mutant did not colonize lettuce roots, although it was not impaired in growth in laboratory cultures, biofilm formation and swarming motility on agar plates. The RBAM17410 gene, occurring in only a few members of the B. subtilis species complex, was directly involved in plant growth promotion. None of the mutant strains were affected in producing the plant growth hormone auxin. We hypothesize that the nfrA gene product is essential for overcoming the stress caused by plant response towards bacterial root colonization.
Publikation

Farmer, E.E.; Gasperini, D.; Acosta, I.F. The squeeze cell hypothesis for the activation of jasmonate synthesis in response to wounding New Phytol. 204, 282-288, (2014) DOI: 10.1111/nph.12897

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Publikation

Grubb, C. D.; Zipp, B. J.; Kopycki, J.; Schubert, M.; Quint, M.; Lim, E.-K.; Bowles, D. J.; Pedras, M. S. C.; Abel, S. Comparative analysis of Arabidopsis UGT74 glucosyltransferases reveals a special role of UGT74C1 in glucosinolate biosynthesis Plant J. 79, 92–105, (2014) DOI: 10.1111/tpj.12541

The study of glucosinolates and their regulation has provided a powerful framework for the exploration of fundamental questions about the function, evolution, and ecological significance of plant natural products, but uncertainties about their metabolism remain. Previous work has identified one thiohydroximate S-glucosyltransferase, UGT74B1, with an important role in the core pathway, but also made clear that this enzyme functions redundantly and cannot be the sole UDP-glucose dependent glucosyltransferase (UGT) in glucosinolate synthesis. Here, we present the results of a nearly comprehensive in vitro activity screen of recombinant Arabidopsis Family 1 UGTs, which implicate other members of the UGT74 clade as candidate glucosinolate biosynthetic enzymes. Systematic genetic analysis of this clade indicates that UGT74C1 plays a special role in the synthesis of aliphatic glucosinolates, a conclusion strongly supported by phylogenetic and gene expression analyses. Finally, the ability of UGT74C1 to complement phenotypes and chemotypes of the ugt74b1-2 knockout mutant and to express thiohydroximate UGT activity in planta provides conclusive evidence for UGT74C1 being an accessory enzyme in glucosinolate biosynthesis with a potential function during plant adaptation to environmental challenge.
Publikation

Delker, C.; Sonntag, L.; Geo, V. J.; Janitza, P.; Ibañez, C.; Ziermann, H.; Peterson, T.; Denk, K.; Mull, S.; Ziegler, J.; Davis, S. J.; Schneeberger, K.; Quint, M. The DET1-COP1-HY5 Pathway Constitutes a Multipurpose Signaling Module Regulating Plant Photomorphogenesis and Thermomorphogenesis Cell Rep 9, 1983–1989, (2014) DOI: 10.1016/j.celrep.2014.11.043

Developmental plasticity enables plants to respond to elevated ambient temperatures by adapting their shoot architecture. On the cellular level, the basic-helix-loop-helix (bHLH) transcription factor PHYTOCHROME INTERACTING FACTOR 4 (PIF4) coordinates this response by activating hormonal modules that in turn regulate growth. In addition to an unknown temperature-sensing mechanism, it is currently not understood how temperature regulates PIF4 activity. Using a forward genetic approach in Arabidopsis thaliana, we present extensive genetic evidence demonstrating that the DE-ETIOLATED 1 (DET1)-CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1)-ELONGATED HYPOCOTYL 5 (HY5)-dependent photomorphogenesis pathway transcriptionally regulates PIF4 to coordinate seedling growth in response to elevated temperature. Our findings demonstrate that two of the most prevalent environmental cues, light and temperature, share a much larger set of signaling components than previously assumed. Similar to the toolbox concept in animal embryonic patterning, multipurpose signaling modules might have evolved in plants to translate various environmental stimuli into adaptational growth processes
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
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