In Brassicaceae werden bei einer Gewebszerstörung unreaktive Glukosinolate durch das Enzym Myrosinase hydrolysiert. Es entstehen reaktive Substanzen wie Isothiocyanate (ITCs). Da diese Reaktion sehr schnell erfolgt wird sie auch als Senföl-Glukosid-Bombe bezeichnet. In Arabidopsis thaliana erfolgt nach Verwundung und Pathogeninfektion eine massive Akkumulation des ITCs Sulforaphan (SF), welches eine reaktive elektophile Spezies (RES) darstellt. Zu der Gruppe der RES zählen auch einige Oxylipine mit einer α,β-ungesättigten Carbonylgruppen wie 12-oxo-Phytodiensäure (OPDA) oder Phytoprostan A1 (PPA1). Die Fähigkeit der kovalenten Modifikation von Peptiden und Proteinen gilt als essentiell sowohl für die toxischen als auch die Gen-induzierenden Eigenschaften der RES. Neben ihrer Reaktivität spielt auch die Lipophilie eine Rolle für die Fähigkeit über Membranen zu diffundieren und unspezifisch an Proteine zu binden. Die in der vorliegenden Arbeit durchgeführten Transkriptomanalysen an Arabidopsis-Keimlingen mit sub-toxischen Konzentrationen von SF, Benzylisothiocyanat (BITC) und dem Oxylipin Prostaglandin A1 (PGA1) zeigten, dass strukturell sehr verschiedene RES einen gemeinsamen Satz von 55 Genen induzieren. Unter diesen befanden sich verschiedene Hitzeschock-, Stressassoziierte- und Detoxifizierungsgene. Diese Ergebnisse deuten darauf hin, dass die Aktivierung über eine Muster-spezifische Erkennung der RES erfolgt. Als einen möglichen Mechanismus der RES-vermittelten Geninduktion wird die Regulation durch die Veränderung des zellulären Redox-Potentials als Folge kovalenter Modifikation von GSH durch RES diskutiert. Die Untersuchung der GSH-Gehalte sowie des Redox-Potential nach Behandlung mit sub-toxischen RES-Konzentrationen in Arabidopsis-Keimlingen zeigte jedoch unter den getesteten Bedingungen keine Veränderung. Neben dem Erkennungs- und Signaltransduktionsmechanismus ist auch die biologische Bedeutung von RES für die Vermittlung einer Stresstoleranz noch weitgehend unklar. Durch die Untersuchung der Genexpression in Arabidopsis-Pflanzen nach Verwundung konnte gezeigt werden, dass eine wundinduzierte Akkumulation von SF zur Induktion einiger Gene der Hitzeschockreaktion (HSR) im Wildtyp, jedoch nicht in der myrosinase-defiziten tgg1tgg2-Mutante führte. Auch in der Transkriptomanalyse war nach RES-Gabe ebenfalls eine starke Induktion hitze-responsiver Gene, deren Regulation über den Masterregulator dem Hitzeschock-TF A1 vermittelt wird, zu beobachten. Besonders die Induktion der HSPs, welche als Chaperone fungieren und damit Thiolgruppen von Proteinen vor Modifikation schützen können, haben vermutlich bei chemischer Intoxikation protektive Eigenschaften für die Zellen. Tatsächlich zeigte sich unter den gewählten Bedingungen die hsfa1a,b,d,e-Mutante empfindlicher gegenüber ITCs als der Wildtyp. Die Fähigkeit, eine HSR ausbilden zu können, scheint in Arabidopsis bei chemischer Intoxikation eine bedeutende Rolle zu spielen. Eine Vorbehandlung mit RES wie SF, BITC oder dem HSP90-Inhibitor Radicicol in Arabidopsis-Keimlingen konnte eine Schutzwirkung vor chemischer Intoxikation vermitteln. Dies erfolgte jedoch nicht nach Behandlung mit moderater Hitze (zwei Stunden, 37 °C). Somit scheint die HSR alleine nicht ausreichend für den Aufbau eines effektiven Schutzes vor BITC-Intoxikation zu sein. Als metabolische Antwort von Arabidopsis-Keimlingen auf Intoxikation mit RES konnte eine konzentrationsabhängige Senkung der maximalen Quantenausbeute am Photosystem II (PSII), sowie gleichzeitig eine Akkumulation an TAG-Spezies beobachtet werden. Diese metabolische Reaktion ist in der Literatur bereits als Schutz gegen Hitzestress beschrieben. Die Bedeutung der TAG-Akkumulation nach chemischem ITC-Stress ist noch unklar. / In Brassicaceae, unreactive glucosinolates are hydrolyzed by the enzyme myrosinase during tissue destruction. Reactive substances such as isothiocyanates (ITCs) are formed. Since this reaction takes place very quickly, it is also called mustard oil bomb. In Arabidopsis thaliana, after wounding and pathogen infection, a massive accumulation of the ITC Sulforaphan (SF) occurs, which is a reactive electophilic species (RES). The group of RES also includes some oxylipins with a α,β-unsaturated carbonyl group such as 12-oxo-phytodienoic acid (OPDA) or phytoprotane A1 (PPA1). The ability to covalently modify peptides and proteins is considered essential for the toxic and gene inducing properties of RES. In addition to their reactivity, lipophilia also plays a role in the ability to diffuse across membranes and bind unspecifically to proteins. The transcriptome analyses performed on Arabidopsis-seedlings with sub-toxic concentrations of SF, benzylisothiocyanate (BITC) and oxylipin prostaglandin A1 (PGA1) showed that structurally very different RES induce a common set of 55 genes. Among the induced genes were several heat shock, stress associated and detoxification genes. These observations suggest that activation is via pattern-specific recognition of RES. As a possible mechanism of RES-mediated gene induction, regulation by alteration of the cellular redox potential as result of covalent modification of GSH by RES is discussed. However, the study of GSH levels and redox potential after treatment with sub-toxic RES concentrations in Arabidopsis-seedlings showed no change under the tested conditions. In addition to the recognition and signal transduction mechanism for RES, the biological significance of RES for the mediation of stress tolerance is still largely unclear. By studying the gene expression of Arabidopsis-plants after wounding, it was shown that wound induced accumulation of SF led to the induction of some genes of heat shock response (HSR) in the wild type, but not in the myrosinase-deficient tgg1tgg2-mutant. Also in transcriptome analysis a strong induction of heat-responsive genes could be observed after RES administration, whose regulation is mediated by the master regulator of the heatshock-TF A1 (HSFA1). In particular, the induction of HSPs, which act as chaperones and can thus protect thiol groups of proteins from modification, presumably have protective properties for the cells during chemical intoxication. In fact, under the conditions tested, the hsfa1a,b,d,e-mutants were more sensitive to ITCs than the wild type. The ability to form HSR seems to play an important role in chemical intoxication in Arabidopsis. Pretreatment with RES such as SF, BITC or the HSP90 inhibitor radicicol in Arabidopsis-seedlings could mediate a protective effect against chemical intoxication. However, this was not done after treatment with moderate heat (two hours, 37 °C). Thus, HSR alone does not seem to be sufficient to provide effective protection against BITC intoxication. As a metabolic response of Arabidopsis-seedlings to intoxication with RES, a concentration-dependent reduction of the maximum quantum yield at the photosystem II (PSII), as well as an accumulation of TAG species could be observed. This metabolic reaction is already described in the literature as protection against heat stress. The significance of TAG accumulation after chemical stress in the form of ITC intoxication is still unclear.

Ulm, Univ., Diss., 2008.

Würzburg, Univ., Diss., 2008

Brassicaceae and a few related plant families are characterized by possession of the glucosinolate-myrosinase system. Glucosinolates are amino-acid derived allelochemicals which are hydrolysed upon tissue damage by myrosinase enzymes to produce various degradation products which can be toxic for generalist insects. The larvae of the crucifer-specialist Athalia rosae, the turnip sawfly, sequester glucosinolates into their haemolymph. The role of the glucosinolate-myrosinase system for the interaction of the turnip sawfly with Brassicaceae was examined in this study from two different perspectives: variation within individual plants and between plant species. The plant responses to the feeding by herbivores and the short-term effects this induction had on insect behaviour were investigated in white mustard. Furthermore, plants can use multiple defences. Hence correlations of glucosinolates and myrosinase activities with other defences and nutritional quality and their long-term effects on the development of the insects were investigated in seven different plant species. / Die Brassicaceen und einige nah verwandte Pflanzenfamilien zeichnen sich durch den Besitz des Glucosinolat-Myrosinase Systems aus. Glucosinolate sind von Aminosäuren abgeleitete Allelochemikalien, die nach Gewebezerstörung von Myrosinaseenzymen hydrolysiert werden. Die entstehenden Abbauprodukte wirken auf generalistische Insekten toxisch. Larven der auf Brassicaceen spezialisierten Rübsenblattwespe, Athalia rosae, sequestrieren Glucosinolate in ihre Hämolymphe. In der vorliegenden Studie wird die Rolle des Glucosinolat-Myrosinase Systems für die Interaktion von Brassicaceen mit der Rübsenblattwespe aus zwei unterschiedlichen Perspektiven untersucht: Variationen innerhalb einzelner Pflanzen und zwischen verschiedenen Pflanzenarten. Die pflanzliche Antwort innnerhalb einzelner Individuen auf Herbivorenfraß und deren kurzzeitige Auswirkungen auf das Insektenverhalten wurden am Weißen Senf untersucht. Des Weiteren nutzen Pflanzen multiple Abwehrmethoden. Daher wurden Korrelationen des Glucosinolat-Myrosinase Systems mit anderen Abwehrmethoden und mit dem Nährstoffgehalt der Pflanzen sowie deren langfristige Effekte auf die Entwicklung der Insekten an sieben verschiedenen Pflanzenarten untersucht.

When exposed to either abiotic or biotic stressors, plants release chemical compounds that can serve as defense mechanisms. For example, plants of the mustard and cabbage family produce a class of anti-herbivory compounds called glucosinolates. In the model mustard plant Arabidopsis thaliana, some glucosinolates are produced from the amino acid tryptophan and are called indole glucosinolates (IGs). Expression of IG synthesis genes is positively regulated by the partially redundant transcription factors, MYB34 and MYB51. Recent studies have shown that these two transcription factors have distinct roles in regulating IG production in different tissues and in mediating responses to different environmental cues. To understand the distinct roles of these transcription factors at a more detailed temporal and spatial level, reporters for CYP79B2, a transcriptional target of both MYB34 and MYB51, were used. CYP79B2-GFP and CYP79B2-GUS reporter expression was analyzed in wild-type and MYB34 and MYB51 mutant plants in response to increased ambient temperature, increased light intensity, ATP exposure, and chitin exposure. Reverse-phase HPLC quantification of IGs was also performed to determine how these transcription factors are mediating the synthesis of IGs in response stressors. Overall, it was found that MYB51 is responsible for the temperature induction of IG production, while increased light intensity has no impact on IG synthesis. Furthermore, ATP appears to induce IG production independently of both MYB34 and MYB51, while chitin does not increase IG synthesis. Taken together, these studies allow us to better understand how plants respond to and defend themselves from different abiotic and biotic stress / 2025-02-26T00:00:00Z

2024 / Rapid fluctuations in the environment caused by climate change have created new challenges for agriculture as many crop species will be more frequently exposed to abiotic stresses they are not adapted for. Since plants typically respond to stress by producing defense compounds, climate change will likely alter plant metabolism. Therefore, understanding the molecular mechanisms regulating plant defense in relation to metabolism can inform methods for engineering more stress-tolerant plants. In the Celenza lab, past experiments have focused on studying defense compounds derived from the tryptophan pathway in Arabidopsis thaliana, a convenient model plant species. This thesis builds on past experiments by quantifying chemical production and gene expression in mutants with significantly altered tryptophan metabolism to determine the systems level effects of altering this metabolic pathway. This research focuses on eight different Arabidopsis mutant strains that have single or combined mutations that alter tryptophan synthesis and/or catabolism. Each mutation changes levels of tryptophan and/or tryptophan-derived defense compounds which was verified with HPLC analysis. In most cases, these mutations also affect overall plant health. Using mRNA extraction followed by RT-qPCR, data reveals that tryptophan-derived defense compound biosynthetic genes such as CYP79B2 have significantly elevated gene expression in most of the mutants tested when compared to wild type. This suggests that both increased and decreased tryptophan metabolism trigger a defense response. These results were followed up using differential gene expression analysis of RNA-seq data and GO-term enrichment to assess global transcriptional changes. From this data we found that tryptophan mutants also have alterations in expression of genes involved in photosynthetic processes. To further explore this, mutants were tested for metabolic responses to abiotic stressors such as high light intensity and increased ambient temperature and showed differential production of defense compounds in response to these stressors. Overall, these findings suggest that perturbing tryptophan metabolism has system-wide effects that can impact plant growth and defense. / 2026-03-05T00:00:00Z

Les glucosinolates (GLs) sont des métabolites secondaires très présents dans la famille des Brassicaceae, une famille de végétaux connus dans l’alimentation humaine pour leurs propriétés gustatives et aussi pour leurs effets chimio-préventifs. La myrosinase (E.C. 3.2.1.147) est la seule enzyme capable d’hydrolyser les GLs. Nous nous sommes intéressés aux produits obtenus lors de cette dégradation - les isothiocyanates (ITCs) mais aussi à la fonction thiohydroximate, et plus particulièrement à la synthèse de nitrones thiofonctionnalisées. La synthèse d’analogues d’ITC ainsi que de certains de leurs thio-conjugués a conduit à une large gamme de molécules permettant de cerner les implications chimio-préventives et les potentiels en bio-activité (notamment contre Plasmodium falciparum). Partant d’observations analytiques relatives à certains GLs comme la glucoraphénine, il a été découvert qu’un thiohydroximate pouvait présenter un caractère nucléophile comparable à celui d’une oxime dans un processus cyclisant du type Grigg. Nous avons dès lors cherché à développer de nouvelles voies d’accès à un système fonctionnel très peu décrit dans la littérature : les N-oxydes de thioimidate (OTI). Une étude de réactivité d’un OTI-modèle a révélé des comportements originaux, en particulier dans des réactions de couplage pallado-catalysées qui ouvrent un accès à des nitrones cycliques originales et peu aisées à préparer par des voies plus classiques. / Glucosinolates (GLs) are widespread secondary metabolites in Brassicaceae, a family of vegetables known in human feeding for their tastes and also for their chemo-prevention effects. Myrosinase (E.C. 3.2.1.147) is the only enzyme able to hydrolyze GLs. We have been interested in products acquired during this degradation - isothiocyanates (ITCs) but also in the thiohydroximate function, and more particularly in the synthesis of thiofunctionalized nitrones. The synthesis of ITC analogues as well as some of their thio-conjugates has led to a broad range of molecules allowing to surround chemo-preventive involvements and potentials in bio-activity (namely against Plasmodium falciparum). Starting from analytical observations related to some GLs such as glucoraphenin, it has been disclosed that a thiohydroximate could display a nucleophilic character comparable to that of an oxime in a Grigg-type cyclic process. We have developed new pathways to a scarcely described functional system : thioimidate N-oxides (OTI). Reactivity studies on a model-OTI have revealed an atypical behaviour, notably in palladium-catalyzed coupling reactions : those open the way to original cyclic nitrones which are not easily available via standard methods.

No description available.

Reproduction de : Thèse de doctorat : Pharmacie. Pharmacognosie : Reims : 2007. / Bibliographie multiples.

Zugl.: Berlin, Humboldt-Univ., Diplomarbeit