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Publikation

Wasternack, C. & Feussner, I. The Oxylipin Pathways: Biochemistry and Function Annu Rev Plant Biol 69, 363-386, (2018) DOI: 10.1146/annurev-arplant-042817-040440

Plant oxylipins form a constantly growing group of signaling molecules that comprise oxygenated fatty acids and metabolites derived therefrom. In the last decade, the understanding of biosynthesis, metabolism, and action of oxylipins, especially jasmonates, has dramatically improved. Additional mechanistic insights into the action of enzymes and insights into signaling pathways have been deepened for jasmonates. For other oxylipins, such as the hydroxy fatty acids, individual signaling properties and cross talk between different oxylipins or even with additional phytohormones have recently been described. This review summarizes recent understanding of the biosynthesis, regulation, and function of oxylipins.
Publikation

Wasternack, C. & Hause, B. A Bypass in Jasmonate Biosynthesis – the OPR3-independent Formation Trends Plant Sci 23, 276-279, (2018) DOI: 10.1016/j.tplants.2018.02.011

For the first time in 25 years, a new pathway for biosynthesis of jasmonic acid (JA) has been identified. JA production takes place via 12-oxo-phytodienoic acid (OPDA) including reduction by OPDA reductases (OPRs). A loss-of-function allele, opr3-3, revealed an OPR3-independent pathway converting OPDA to JA.
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Wasternack, C. & Strnad, M. Jasmonates are signals in the biosynthesis of secondary metabolites — Pathways, transcription factors and applied aspects — A brief review. New Biotechnol. (2017) DOI: 10.1016/j.nbt.2017.09.007

Jasmonates (JAs) are signals in plant stress responses and development. One of the first observed and prominent responses to JAs is the induction of biosynthesis of different groups of secondary compounds. Among them are nicotine, isoquinolines, glucosinolates, anthocyanins, benzophenanthridine alkaloids, artemisinin, and terpenoid indole alkaloids (TIAs), such as vinblastine. This brief review describes modes of action of JAs in the biosynthesis of anthocyanins, nicotine, TIAs, glucosinolates and artemisinin. After introducing JA biosynthesis, the central role of the SCFCOI1-JAZ co-receptor complex in JA perception and MYB-type and MYC-type transcription factors is described. Brief comments are provided on primary metabolites as precursors of secondary compounds. Pathways for the biosynthesis of anthocyanin, nicotine, TIAs, glucosinolates and artemisinin are described with an emphasis on JA-dependent transcription factors, which activate or repress the expression of essential genes encoding enzymes in the biosynthesis of these secondary compounds. Applied aspects are discussed using the biotechnological formation of artemisinin as an example of JA-induced biosynthesis of secondary compounds in plant cell factories.
Publikation

Wasternack, C. & Song, S. Jasmonates: biosynthesis, metabolism, and signaling by proteins activating and repressing transciption J. Exp. Bot. 68, 1303-1321, (2017) DOI: 10.1093/jxb/erw443

The lipid-derived phytohormone jasmonate (JA) regulates plant growth, development, secondary metabolism, defense against insect attack and pathogen infection, and tolerance to abiotic stresses such as wounding, UV light, salt, and drought. JA was first identified in 1962, and since the 1980s many studies have analyzed the physiological functions, biosynthesis, distribution, metabolism, perception, signaling, and crosstalk of JA, greatly expanding our knowledge of the hormone’s action. In response to fluctuating environmental cues and transient endogenous signals, the occurrence of multilayered organization of biosynthesis and inactivation of JA, and activation and repression of the COI1–JAZ-based perception and signaling contributes to the fine-tuning of JA responses. This review describes the JA biosynthetic enzymes in terms of gene families, enzymatic activity, location and regulation, substrate specificity and products, the metabolic pathways in converting JA to activate or inactivate compounds, JA signaling in perception, and the co-existence of signaling activators and repressors

Publikation

Wasternack, C. The Trojan horse coronatine: the COI1–JAZ2–MYC2,3,4–ANAC019,055,072 module in stomata dynamics upon bacterial infection. New Phytol 213, 972-975, (2017) DOI: 10.1111/nph.14417

Coronatine (COR) is a phytotoxin produced by a plasmid-encoded operon of genes in several strains of Pseudomonas syringae (Bender et al., 1999). It is a mimic of the defense-associated phytohormone jasmonic acid isoleucine and delivered by the phytopathogenic bacterium to gain access to host plants through stomatal entry and to repress a specific sector of plant immunity. In this issue of New Phytologist (pp. 1378–1392) Gimenez-Ibanez et al. reveal exciting insights into the transcriptional regulation of COR/jasmonic acid isoleucine-governed transcriptional networks modulating stomatal aperture during bacterial invasion.

Publikation

Wasternack, C. & Strnad, M. Jasmonate signaling in plant stress responses and development – active and inactive compounds New Biotechnology 33 B, 604-613, (2016) DOI: 10.1016/j.nbt.2015.11.001

Jasmonates (JAs) are lipid-derived signals mediating plant responses to biotic and abiotic stresses and in plant development. Following the elucidation of each step in their biosynthesis and the important components of perception and signaling, several activators, repressors and co-repressors have been identified which contribute to fine-tuning the regulation of JA-induced gene expression. Many of the metabolic reactions in which JA participates, such as conjugation with amino acids, glucosylation, hydroxylation, carboxylation, sulfation and methylation, lead to numerous compounds with different biological activities. These metabolites may be highly active, partially active in specific processes or inactive. Hydroxylation, carboxylation and sulfation inactivate JA signaling. The precursor of JA biosynthesis, 12-oxo-phytodienoic acid (OPDA), has been identified as a JA-independent signaling compound. An increasing number of OPDA-specific processes is being identified. To conclude, the numerous JA compounds and their different modes of action allow plants to respond specifically and flexibly to alterations in the environment.

Publikation

Floková, K., Feussner, K., Herrfurth, C., Miersch, O., Mik, V., Tarkowská, D., Strnad, M., Feussner, I., Wasternack, C. & Novák, O. A previously undescribed jasmonate compound in flowering Arabidopsis thaliana – The identification of cis-(+)-OPDA-Ile. Phytochemistry 122, 230-237, (2016) DOI: 10.1016/j.phytochem.2015.11.012

Jasmonates (JAs) are plant hormones that integrate external stress stimuli with physiological responses. (+)-7-iso-JA-L-Ile is the natural JA ligand of COI1, a component of a known JA receptor. The upstream JA biosynthetic precursor cis-(+)-12-oxo-phytodienoic acid (cis-(+)-OPDA) has been reported to act independently of COI1 as an essential signal in several stress-induced and developmental processes. Wound-induced increases in the endogenous levels of JA/JA-Ile are accompanied by two to tenfold increases in the concentration of OPDA, but its means of perception and metabolism are unknown. To screen for putative OPDA metabolites, vegetative tissues of flowering Arabidopsis thaliana were extracted with 25% aqueous methanol (v/v), purified by single-step reversed-phase polymer-based solid-phase extraction, and analyzed by high throughput mass spectrometry. This enabled the detection and quantitation of a low abundant OPDA analog of the biologically active (+)-7-iso-JA-L-Ile in plant tissue samples. Levels of the newly identified compound and the related phytohormones JA, JA-Ile and cis-(+)-OPDA were monitored in wounded leaves of flowering Arabidopsis lines (Col-0 and Ws) and compared to the levels observed in Arabidopsis mutants deficient in the biosynthesis of JA (dde2-2, opr3) and JA-Ile (jar1). The observed cis-(+)-OPDA-Ile levels varied widely, raising questions concerning its role in Arabidopsis stress responses.

Publikation

Gasperini, D., Chauvin, A., Acosta, I.F., Kurenda, A., Stolz, S., Chétalat, A., Wolfender J.-L. & Farmer, E.E. Axial and Radial Oxylipin Transport. Plant Physiol. 169, 2244-2254, (2015) DOI: 10.1104/pp.15.01104

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Publikation

Gasperini, D., Chételat, A., Acosta, I.F., Goossens, J., Pauwels, L., Goossens, A., Dreos, R., Alonso, E. & Farmer, E.E. Multilayered Organization of Jasmonate Signalling in the Regulation of Root Growth PLoS Genet. 11 (6), e1005300, (2015) DOI: 10.1371/journal.pgen.1005300

Physical damage can strongly affect plant growth, reducing the biomass of developing organs situated at a distance from wounds. These effects, previously studied in leaves, require the activation of jasmonate (JA) signalling. Using a novel assay involving repetitive cotyledon wounding in Arabidopsis seedlings, we uncovered a function of JA in suppressing cell division and elongation in roots. Regulatory JA signalling components were then manipulated to delineate their relative impacts on root growth. The new transcription factor mutant myc2-322B was isolated. In vitro transcription assays and whole-plant approaches revealed that myc2-322B is a dosage-dependent gain-of-function mutant that can amplify JA growth responses. Moreover, myc2-322B displayed extreme hypersensitivity to JA that totally suppressed root elongation. The mutation weakly reduced root growth in undamaged plants but, when the upstream negative regulator NINJA was genetically removed, myc2-322B powerfully repressed root growth through its effects on cell division and cell elongation. Furthermore, in a JA-deficient mutant background, ninja1 myc2-322B still repressed root elongation, indicating that it is possible to generate JA-responses in the absence of JA. We show that NINJA forms a broadly expressed regulatory layer that is required to inhibit JA signalling in the apex of roots grown under basal conditions. By contrast, MYC2, MYC3 and MYC4 displayed cell layer-specific localisations and MYC3 and MYC4 were expressed in mutually exclusive regions. In nature, growing roots are likely subjected to constant mechanical stress during soil penetration that could lead to JA production and subsequent detrimental effects on growth. Our data reveal how distinct negative regulatory layers, including both NINJA-dependent and -independent mechanisms, restrain JA responses to allow normal root growth. Mechanistic insights from this work underline the importance of mapping JA signalling components to specific cell types in order to understand and potentially engineer the growth reduction that follows physical damage.

Publikation

Wasternack, C. How Jasmonates Earned their Laurels: Past and Present Journal of Plant Growth Regulation 34 (4), 761-794, (2015) DOI: 10.1007/s00344-015-9526-5

The histories of research regarding all plant hormones are similar. Identification and structural elucidation have been followed by analyses of their biosynthesis, distributions, signaling cascades, roles in developmental or stress response programs, and crosstalk. Jasmonic acid (JA) and its derivatives comprise a group of plant hormones that were discovered recently, compared to auxin, abscisic acid, cytokinins, gibberellic acid, and ethylene. Nevertheless, there have been tremendous advances in JA research, following the general progression outlined above and parallel efforts focused on several other “new” plant hormones (brassinosteroids, salicylate, and strigolactones). This review focuses on historical aspects of the identification of jasmonates, and characterization of their biosynthesis, distribution, perception, signaling pathways, crosstalk with other hormones and roles in plant stress responses and development. The aim is to illustrate how our present knowledge on jasmonates was generated and how that influences current efforts to extend our knowledge.

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