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Publikationen - Molekulare Signalverarbeitung

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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 Signaling Pathways Plant Physiol. 123, 177-188, (2000) DOI: 10.1104/pp.123.1.177

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 h before OPDA and OPDAME. However, OPDA accumulated up to a 2.5-fold higher level than the other compounds. Dihomo-JA and 9,13-didehydro-OPDA 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, as evidenced by those genes that did not respond to endogenously formed JA. Also, coronatine induces JA-responsive genes independently from endogenous JA. Application of deuterated JA showed that endogenous synthesis of JA is not induced by JA treatment. The data are discussed in terms of distinct signaling pathways.
Publikation

Herde, O.; Peña Cortés, H.; Wasternack, C.; Willmitzer, L.; Fisahn, J.; Electric Signaling and Pin2 Gene Expression on Different Abiotic Stimuli Depend on a Distinct Threshold Level of Endogenous Abscisic Acid in Several Abscisic Acid-Deficient Tomato Mutants Plant Physiol. 119, 213-218, (1999) DOI: 10.1104/pp.119.1.213

Experiments were performed on three abscisic acid (ABA)-deficient tomato (Lycopersicon esculentum Mill.) mutants, notabilis,flacca, and sitiens, to investigate the role of ABA and jasmonic acid (JA) in the generation of electrical signals and Pin2 (proteinaseinhibitor II) gene expression. We selected these mutants because they contain different levels of endogenous ABA. ABA levels in the mutant sitiens were reduced to 8% of the wild type, in notabilis they were reduced to 47%, and in flacca they were reduced to 21%. In wild-type and notabilis tomato plants the induction ofPin2 gene expression could be elicited by heat treatment, current application, or mechanical wounding. Inflacca and sitiens only heat stimulation induced Pin2 gene expression. JA levels inflacca and sitiens plants also accumulated strongly upon heat stimulation but not upon mechanical wounding or current application. Characteristic electrical signals evolved in the wild type and in the notabilis andflacca mutants consisting of a fast action potential and a slow variation potential. However, in sitiens only heat evoked electrical signals; mechanical wounding and current application did not change the membrane potential. In addition, exogenous application of ABA to wild-type tomato plants induced transient changes in membrane potentials, indicating the involvement of ABA in the generation of electrical signals. Our data strongly suggest the presence of a minimum threshold value of ABA within the plant that is essential for the early events in electrical signaling and mediation of Pin2 gene expression upon wounding. In contrast, heat-induced Pin2 gene expression and membrane potential changes were not dependent on the ABA level but, rather, on the accumulation of JA.
Publikation

Herde, O.; Atzorn, R.; Fisahn, J.; Wasternack, C.; Willmitzer, L.; Pena-Cortes, H.; Localized Wounding by Heat Initiates the Accumulation of Proteinase Inhibitor II in Abscisic Acid-Deficient Plants by Triggering Jasmonic Acid Biosynthesis Plant Physiol. 112, 853-860, (1996) DOI: 10.1104/pp.112.2.853

To test whether the response to electrical current and heat treatment is due to the same signaling pathway that mediates mechanical wounding, we analyzed the effect of electric-current application and localized burning on proteinase inhibitor II (Pin2) gene expression in both wild-type and abscisic acid (ABA)-deficient tomato (Lycopersicon esculentum Mill.) and potato (Solanum phureja) plants. Electric-current application and localized burning led to the accumulation of Pin2 mRNA in potato and tomato wild-type plants. Among the treatments tested, only localized burning of the leaves led to an accumulation of Pin2 mRNA in the ABA-deficient plants. Electric-current application, like mechanical injury, was able to initiate ABA and jasmonic acid (JA) accumulation in wild-type but not in ABA-deficient plants. In contrast, heat treatment led to an accumulation of JA in both wild-type and ABA-deficient plants. Inhibition of JA biosynthesis by aspirin blocked the heat-induced Pin2 gene expression in tomato wild-type leaves. These results suggest that electric current, similar to mechanical wounding, requires the presence of ABA to induce Pin2 gene expression. Conversely, burning of the leaves activates Pin2 gene expression by directly triggering the biosynthesis of JA by an alternative pathway that is independent of endogenous ABA levels.
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