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Publikationen - Molekulare Signalverarbeitung

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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

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

Acosta, I.F., Gasperini, D., Chételat, A., Stolz, S., Santuari, L. & Farmer, E.E. Role of NINJA in root jasmonate signaling. In: PNAS 110 (38), 15473-15478, (2013) DOI: 10.1073/pnas.1307910110

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Publikation

Lee, C-W., Efetova, M., Engelmann, J.C., Kramell, R., Wasternack, C., Ludwig- Müller, J., Hedrich, R. & Deeken, R. Agrobacterium tumefaciens promotes tumor induction by modulating pathogen defense in Arabidopsis thaliana. The Plant Cell 21, 2948 - 2962, (2009) DOI: 10.1105/tpc.108.064576

Agrobacterium tumefaciens causes crown gall disease by transferring and integrating bacterial DNA (T-DNA) into the plant genome. To examine the physiological changes and adaptations during Agrobacterium-induced tumor development, we compared the profiles of salicylic acid (SA), ethylene (ET), jasmonic acid (JA), and auxin (indole-3-acetic acid [IAA]) with changes in the Arabidopsis thaliana transcriptome. Our data indicate that host responses were much stronger toward the oncogenic strain C58 than to the disarmed strain GV3101 and that auxin acts as a key modulator of the Arabidopsis–Agrobacterium interaction. At initiation of infection, elevated levels of IAA and ET were associated with the induction of host genes involved in IAA, but not ET signaling. After T-DNA integration, SA as well as IAA and ET accumulated, but JA did not.

This did not correlate with SA-controlled pathogenesis-related gene expression in the host, although high SA levels in mutant plants prevented tumor development, while low levels promoted it. Our data are consistent with a scenario in which ET and later on SA control virulence of agrobacteria, whereas ET and auxin stimulate neovascularization during tumor formation. We suggest that crosstalk among IAA, ET, and SA balances pathogen defense launched by the host and tumorgrowth initiated by agrobacteria.

Publikation

Mugford, S.G., Yoshimoto, N., Reichelt, M., Wirtz, M., Hill, L., Mugford, S.T., Nakazato, Y., Noji, M., Takahashi, H., Kramell, R., Gigolashvili, T., Flügge, U.-I., Wasternack, C., Gershenzon, J., Hell, R., Saito, K. & Kopriva, S. Disruption of Adenosine-5'-Phosphosulfate Kinase in ArabidopsisReduces Levels of Sulfated Secondary Metabolites Plant Cell 21, 910-927, (2009)

Plants can metabolize sulfate by two pathways, which branch at the level of adenosine 59-phosphosulfate (APS). APS can be reduced to sulfide and incorporated into Cys in the primary sulfate assimilation pathway or phosphorylated by APS kinase to 39-phosphoadenosine 59-phosphosulfate, which is the activated sulfate form for sulfation reactions. To assess to what extent APS kinase regulates accumulation of sulfated compounds, we analyzed the corresponding gene family in Arabidopsis thaliana. Analysis of T-DNA insertion knockout lines for each of the four isoforms did not reveal any phenotypical alterations. However, when all six combinations of double mutants were compared, the apk1 apk2 plants were significantly smaller than wild-type plants. The levels of glucosinolates, a major class of sulfated secondary metabolites, and the sulfated 12-hydroxyjasmonate were reduced approximately fivefold in apk1 apk2 plants. Although auxin levels were increased in the apk1 apk2 mutants, as is the case for most plants with compromised glucosinolate synthesis, typical high auxin phenotypes were not observed. The reduction in glucosinolates resulted in increased transcript levels for genes involved in glucosinolate biosynthesis and accumulation of desulfated precursors. It also led to great alterations in sulfur metabolism: the levels of sulfate and thiols increased in the apk1 apk2 plants. The data indicate that the APK1 and APK2 isoforms of APS kinase play a major role in the synthesis of secondary sulfated metabolites and are required for normalgrowth rates.

Publikation

Abdala, G., Miersch, O., Kramell, R., Vigliocco, A., Agostini, E., Forchetti, G. & Alemano, S. Jasmonate and octadecanoid occurrence in tomato hairy roots. Endogenous level changes in response to NaCl Plant Growth Regul. 40, 21-27, (2003)

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Publikation

Hause, B., Maier, W., Miersch, O., Kramell, R. & Strack, D. Induction of jasmonate biosynthesis in arbuscular mycorrhizal barley roots Plant Physiol. 130, 1213-1220, (2002)

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Publikation

Kramell, R., Miersch, O., Atzorn, R., Parthier, B. & Wasternack, C. Octadecanoid-derived alteration of gene expression and the 'oxylipin signature' in stressed barley leaves - implications for different signalling pathways Plant Physiol. 123, 177-186, (2000)

Stress-induced gene expression in barley (Hordeum vulgare cv. Salome) leaves has been correlated with temporally changing levels of octadecanoids and jasmonates, quantified by means of gas chromatography/mass spectrometry-single ion monitoring. Application of sorbitol-induced stress led to a low and transient rise of jasmonic acid (JA), its precursor 12-oxophytodienoic acid (OPDA) and the methyl esters JAME and OPDAME, respectively, followed by a large increase in their levels. JA and JAME peaked between 12 and 16 h, about 4 hours before OPDA and OPDAME. However, OPDA accumulated up to a 2.5-fold higher level than the other compounds. Dihomo-jasmonic acid and 9,13-didehydro-12- oxophytoenoic acid were identified as minor components. Kinetic analyses revealed that a transient threshold of jasmonates or octadecanoids is necessary and sufficient to initiate JA responsive gene expression. Although OPDA and OPDAME applied exogenously were metabolized to JA in considerable amounts, both of them can induce gene expression per se as evidenced by those genes which do not respond to endogenously formed JA. Also, coronatine induces JA-responsive genes independently from endogenous JA. As evidenced by application of deuterated JA, endogenous synthesis of JA is not induced by JA treatment. The data are discussed in terms of distinct signalling pathways.
Publikation

Kramell, R., Miersch, O., Schneider, G. & Wasternack, C. Liquid chromatography of jasmonic acid amine conjugates Chromatographia 49, 42-46, (1999)

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