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Publikationen - Molekulare Signalverarbeitung

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Publikation

Ludwig, A. A.; Saitoh, H.; Felix, G.; Freymark, G.; Miersch, O.; Wasternack, C.; Boller, T.; Jones, J. D. G.; Romeis, T.; Ethylene-mediated cross-talk between calcium-dependent protein kinase and MAPK signaling controls stress responses in plants Proc. Natl. Acad. Sci. U.S.A. 102, 10736-10741, (2005) DOI: 10.1073/pnas.0502954102

Plants are constantly exposed to environmental changes and need to integrate multiple external stress cues. Calcium-dependent protein kinases (CDPKs) are implicated as major primary Ca2+ sensors in plants. CDPK activation, like activation of mitogen-activated protein kinases (MAPKs), is triggered by biotic and abiotic stresses, although distinct stimulus-specific stress responses are induced. To investigate whether CDPKs are part of an underlying mechanism to guarantee response specificity, we identified CDPK-controlled signaling pathways. A truncated form of Nicotiana tabacum CDPK2 lacking its regulatory autoinhibitor and calcium-binding domains was ectopically expressed in Nicotiana benthamiana. Infiltrated leaves responded to an abiotic stress stimulus with the activation of biotic stress reactions. These responses included synthesis of reactive oxygen species, defense gene induction, and SGT1-dependent cell death. Furthermore, N-terminal CDPK2 signaling triggered enhanced levels of the phytohormones jasmonic acid, 12-oxo-phytodienoic acid, and ethylene but not salicylic acid. These responses, commonly only observed after challenge with a strong biotic stimulus, were prevented when the CDPK's intrinsic autoinhibitory peptide was coexpressed. Remarkably, elevated CDPK signaling compromised stress-induced MAPK activation, and this inhibition required ethylene synthesis and perception. These data indicate that CDPK and MAPK pathways do not function independently and that a concerted activation of both pathways controls response specificity to biotic and abiotic stress.
Publikation

Gerhardt, B.; Fischer, K.; Balkenhohl, T. J.; Pohnert, G.; Kühn, H.; Wasternack, C.; Feussner, I.; Lipoxygenase-mediated metabolism of storage lipids in germinating sunflower cotyledons and β-oxidation of (9Z,11E,13S)-13-hydroxy-octadeca-9,11-dienoic acid by the cotyledonary glyoxysomes Planta 220, 919-930, (2005) DOI: 10.1007/s00425-004-1408-1

During the early stages of germination, a lipid-body lipoxygenase is expressed in the cotyledons of sunflowers (Helianthus annuus L.). In order to obtain evidence for the in vivo activity of this enzyme during germination, we analyzed the lipoxygenase-dependent metabolism of polyunsaturated fatty acids esterified in the storage lipids. For this purpose, lipid bodies were isolated from etiolated sunflower cotyledons at different stages of germination, and the storage triacylglycerols were analyzed for oxygenated derivatives. During the time course of germination the amount of oxygenated storage lipids was strongly augmented, and we detected triacylglycerols containing one, two or three residues of (9Z,11E,13S)-13-hydro(pero)xy-octadeca-9,11-dienoic acid. Glyoxysomes from etiolated sunflower cotyledons converted (9Z,11E,13S)-13-hydroxy-octadeca-9,11-dienoic acid to (9Z,11E)-13-oxo-octadeca-9,11-dienoic acid via an NADH-dependent dehydrogenase reaction. Both oxygenated fatty acid derivatives were activated to the corresponding CoA esters and subsequently metabolized to compounds of shorter chain length. Cofactor requirement and formation of acetyl-CoA indicate degradation via β-oxidation. However, β-oxidation only proceeded for two consecutive cycles, leading to accumulation of a medium-chain metabolite carrying an oxo group at C-9, equivalent to C-13 of the parent (9Z,11E,13S)-13-hydroxy-octadeca-9,11-dienoic acid. Short-chain β-oxidation intermediates were not detected during incubation. Similar results were obtained when 13-hydroxy octadecanoic acid was used as β-oxidation substrate. On the other hand, the degradation of (9Z,11E)-octadeca-9,11-dienoic acid was accompanied by the appearance of short-chain β-oxidation intermediates in the reaction mixture. The results suggest that the hydroxyl/oxo group at C-13 of lipoxygenase-derived fatty acids forms a barrier to continuous β-oxidation by glyoxysomes.
Publikation

Fortes, A. M.; Miersch, O.; Lange, P. R.; Malhó, R.; Testillano, P. S.; Risueño, M. d. C.; Wasternack, C.; Pais, M. S.; Expression of Allene Oxide Cyclase and Accumulation of Jasmonates during Organogenic Nodule Formation from Hop (Humulus lupulus var. Nugget) Internodes Plant Cell Physiol. 46, 1713-1723, (2005) DOI: 10.1093/pcp/pci187

A crucial step in the biosynthesis of jasmonic acid (JA) is the formation of its stereoisomeric precursor, cis-(+)-12-oxophytodienoic acid (OPDA), which is catalyzed by allene oxide cyclase (AOC, EC 5.3.99.6). A cDNA of AOC was isolated from Humulus lupulus var. Nugget. The ORF of 765 bp encodes a 255 amino acid protein, which carries a putative chloroplast targeting sequence. The recombinant protein without its putative chloroplast target sequence showed significant AOC activity. Previously we demonstrated that wounding induces organogenic nodule formation in hop. Here we show that the AOC transcript level increases in response to wounding of internodes, peaking between 2 and 4 h after wounding. In addition, Western blot analysis showed elevated levels of AOC peaking 24 h after internode inoculation. The AOC increase was accompanied by increased JA levels 24 h after wounding, whereas OPDA had already reached its highest level after 12 h. AOC is mostly present in the vascular bundles of inoculated internodes. During prenodule and nodule formation, AOC levels were still high. JA and OPDA levels decreased down to 10 and 118 pmol (g FW)–1, respectively, during nodule formation, but increased during plantlet regeneration. Double immunolocalization analysis of AOC and Rubisco in connection with lugol staining showed that AOC is present in amyloplasts of prenodular cells and in the chloroplasts of vacuolated nodular cells, whereas meristematic cells accumulated little AOC. These data suggest a role of AOC and jasmonates in organogenic nodule formation and plantlet regeneration from these nodules.
Publikation

Sharma, V. K.; Monostori, T.; Hause, B.; Maucher, H.; Göbel, C.; Hornung, E.; Hänsch, R.; Bittner, F.; Wasternack, C.; Feussner, I.; Mendel, R. R.; Schulze, J.; Genetic transformation of barley to modify expression of a 13-lipoxygenase Acta Biol. Szeged. 49, 33-34, (2005)

Immature scutella of barley were transformed with cDNA coding for a 13-lipoxygenase of barley (LOX-100) via particle bombardment. Regenerated plants were tested by PAT-assay, Western-analysis and PCR-screening. Immunocytochemical assay of T0 plants showed expression of the LOX cDNA both in the chloroplasts and in the cytosol, depending on the presence of the chloroplast signal peptide sequences in the cDNA. A few transgenic plants containing higher amounts of LOX-derived products have been found. These are the candidates for further analysis concerning pathogen resistance.
Publikation

Schneider, K.; Kienow, L.; Schmelzer, E.; Colby, T.; Bartsch, M.; Miersch, O.; Wasternack, C.; Kombrink, E.; Stuible, H.-P.; A New Type of Peroxisomal Acyl-Coenzyme A Synthetase from Arabidopsis thaliana Has the Catalytic Capacity to Activate Biosynthetic Precursors of Jasmonic Acid J. Biol. Chem. 280, 13962-13972, (2005) DOI: 10.1074/jbc.M413578200

Arabidopsis thaliana contains a large number of genes that encode carboxylic acid-activating enzymes, including nine long-chain fatty acyl-CoA synthetases, four 4-coumarate:CoA ligases (4CL), and 25 4CL-like proteins of unknown biochemical function. Because of their high structural and sequence similarity with bona fide 4CLs and their highly hydrophobic putative substrate-binding pockets, the 4CL-like proteins At4g05160 and At5g63380 were selected for detailed analysis. Following heterologous expression, the purified proteins were subjected to a large scale screen to identify their preferred in vitro substrates. This study uncovered a significant activity of At4g05160 with medium-chain fatty acids, medium-chain fatty acids carrying a phenyl substitution, long-chain fatty acids, as well as the jasmonic acid precursors 12-oxo-phytodienoic acid and 3-oxo-2-(2′-pentenyl)-cyclopentane-1-hexanoic acid. The closest homolog of At4g05160, namely At5g63380, showed high activity with long-chain fatty acids and 12-oxo-phytodienoic acid, the latter representing the most efficiently converted substrate. By using fluorescent-tagged variants, we demonstrated that both 4CL-like proteins are targeted to leaf peroxisomes. Collectively, these data demonstrate that At4g05160 and At5g63380 have the capacity to contribute to jasmonic acid biosynthesis by initiating the β-oxidative chain shortening of its precursors.
Publikation

Rudus, I.; Kepczynska, E.; Kepczynski, J.; Wasternack, C.; Miersch, O.; Changes in jasmonates and 12-oxophytodienoic acid contents of Medicago sativa L. during somatic embryogenesis Acta Physiol. Plant. 27, 497-504, (2005) DOI: 10.1007/s11738-005-0055-x

Jasmonic acid (JA), its methyl ester (MeJA) and the biosynthetic precursor 12-oxophytodienoic acid (OPDA) were detected quantitatively during somatic embryogenesis of Medicago sativa L. Using GC-MS analysis, these compounds were found in initial explants, in calli and in somatic embryos in the nanogram range per gram of fresh weight. In distinct stages of somatic embryogenesis, JA and 12-OPDA accumulated preferentially in cotyledonary embryos. Initial explants exhibited about five-fold higher JA content than OPDA content, whereas in other stages OPDA accumulated predominantly. These data suggest that also in embryogenic tissues OPDA and JA may have individual signalling properties.
Bücher und Buchkapitel

Vaira, A. M.; Acotto, G. P.; Gago-Zachert, S.; Garcia, M. L.; Grau, O.; Milne, R. G.; Morikawa, T.; Natsuaki, T.; Torov, V.; Verbeek, M.; Vetten, H. J.; Genus Ophiovirus 673-679, (2005) ISBN: 9780080575483 DOI: 10.1016/B978-0-12-249951-7.50014-6

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Publikation

Wasternack, C.; Atzorn, R.; Peña-Cortés, H.; Parthier, B.; Alteration of Gene Expression by Jasmonate and ABA in Tobacco and Tomato J. Plant Physiol. 147, 503-510, (1996) DOI: 10.1016/S0176-1617(96)80038-1

The synthesis of jasmonate-induced proteins in leaves of tobacco (Nicotiana plumbaginifolia) and tomato (Lycopersicon esculentum) was studied in order to find a possible functional link in the actions of abscisic acid (ABA) and jasmonates. ABA-deficient mutants of tobacco (CKR1) and of tomato (sitiens, flacca), and their corresponding wild-types, were compared with respect to endogenous contents of jasmonates and ABA, and polypeptide and transcript patterns in water- or jasmonate-floated leaves, leaves stressed by floating on sorbitol, or by weak desiccation. Our results indicate that in tobacco the synthesis of proteins induced by jasmonate differed from those induced by ABA, whereas in tomato some jasmonate-induced proteins were also induced by ABA. The results provide further evidence that different signalling pathways exist for jasmonate/ABA-responsive gene expression in various plant species.
Publikation

Peña-Cortés, H.; Prat, S.; Atzorn, R.; Wasternack, C.; Willmitzer, L.; Abscisic acid-deficient plants do not accumulate proteinase inhibitor II following systemin treatment Planta 198, 447-451, (1996) DOI: 10.1007/BF00620062

The role of systemin in Pin2 gene expression was analyzed in wild-type plants of potato (Solanum tuberosum L.) and tomato (Lycopersicon esculentum Mill.), as well as in abscisic acid (ABA)-deficient tomato (sitiens) and potato (droopy) plants. The results showed that systemin initiates Pin2 mRNA accumulation only in wildtype tomato and potato plants. As in the situation after mechanical wounding,Pin2 gene expression in ABA-deficient plants was not activated by systemin. Increased endogenous levels of jasmonic acid (JA) and accumulation of Pin2 mRNA were observed following treatment with α-linolenic acid, the precursor of JA biosynthesis, suggesting that these ABA mutants still have the capability to synthesize de novo JA. Measurement of endogenous levels of ABA and JA showed that systemin leads to an increase of both phytohormones (ABA and JA) only in wild-type but not in ABA-deficient plants.
Publikation

O'Donnell, P. J.; Calvert, C.; Atzorn, R.; Wasternack, C.; Leyser, H. M. O.; Bowles, D. J.; Ethylene as a Signal Mediating the Wound Response of Tomato Plants Science 274, 1914-1917, (1996) DOI: 10.1126/science.274.5294.1914

Plants respond to physical injury, such as that caused by foraging insects, by synthesizing proteins that function in general defense and tissue repair. In tomato plants, one class of wound-responsive genes encodes proteinase inhibitor (pin) proteins shown to block insect feeding. Application of many different factors will induce or inhibit pin gene expression. Ethylene is required in the transduction pathway leading from injury, and ethylene and jasmonates act together to regulate pin gene expression during the wound response.
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  • Digitalisierung in der Landwirtschaft
  • Martin-Luther Universität Halle
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