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Publikationen - Molekulare Signalverarbeitung

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Publikation

Leon-Reyes, A.; Van der Does, D.; De Lange, E. S.; Delker, C.; Wasternack, C.; Van Wees, S. C. M.; Ritsema, T.; Pieterse, C. M. J.; Salicylate-mediated suppression of jasmonate-responsive gene expression in Arabidopsis is targeted downstream of the jasmonate biosynthesis pathway Planta 232, 1423-1432, (2010) DOI: 10.1007/s00425-010-1265-z

Jasmonates (JAs) and salicylic acid (SA) are plant hormones that play pivotal roles in the regulation of induced defenses against microbial pathogens and insect herbivores. Their signaling pathways cross-communicate providing the plant with a regulatory potential to finely tune its defense response to the attacker(s) encountered. In Arabidopsis thaliana, SA strongly antagonizes the jasmonic acid (JA) signaling pathway, resulting in the downregulation of a large set of JA-responsive genes, including the marker genes PDF1.2 and VSP2. Induction of JA-responsive marker gene expression by different JA derivatives was equally sensitive to SA-mediated suppression. Activation of genes encoding key enzymes in the JA biosynthesis pathway, such as LOX2, AOS, AOC2, and OPR3 was also repressed by SA, suggesting that the JA biosynthesis pathway may be a target for SA-mediated antagonism. To test this, we made use of the mutant aos/dde2, which is completely blocked in its ability to produce JAs because of a mutation in the ALLENE OXIDE SYNTHASE gene. Mutant aos/dde2 plants did not express the JA-responsive marker genes PDF1.2 or VSP2 in response to infection with the necrotrophic fungus Alternaria brassicicola or the herbivorous insect Pieris rapae. Bypassing JA biosynthesis by exogenous application of methyl jasmonate (MeJA) rescued this JA-responsive phenotype in aos/dde2. Application of SA suppressed MeJA-induced PDF1.2 expression to the same level in the aos/dde2 mutant as in wild-type Col-0 plants, indicating that SA-mediated suppression of JA-responsive gene expression is targeted at a position downstream of the JA biosynthesis pathway.
Publikation

Delker, C.; Raschke, A.; Quint, M.; Auxin dynamics: the dazzling complexity of a small molecule’s message Planta 227, 929-941, (2008) DOI: 10.1007/s00425-008-0710-8

The phytohormone auxin is a potent regulator of plant development. Since its discovery in the beginning of the twentieth century many aspects of auxin biology have been extensively studied, ranging from biosynthesis and metabolism to the elucidation of molecular components of downstream signaling. With the identification of the F-box protein TIR1 as an auxin receptor a major breakthrough in understanding auxin signaling has been achieved and recent modeling approaches have shed light on the putative mechanisms underlying the establishment of auxin gradients and maxima essential for many auxin-regulated processes. Here, we review these and other recent advances in unraveling the entanglement of biosynthesis, polar transport and cellular signaling events that allow small auxinic molecules to facilitate their complex regulatory action.
Publikation

Meixner, C.; Ludwig-Müller, J.; Miersch, O.; Gresshoff, P.; Staehelin, C.; Vierheilig, H.; Lack of mycorrhizal autoregulation and phytohormonal changes in the supernodulating soybean mutant nts1007 Planta 222, 709-715, (2005) DOI: 10.1007/s00425-005-0003-4

Autoregulatory mechanisms have been reported in the rhizobial and the mycorrhizal symbiosis. Autoregulation means that already existing nodules or an existing root colonization by an arbuscular mycorrhizal fungus systemically suppress subsequent nodule formation/root colonization in other parts of the root system. Mutants of some legumes lost their ability to autoregulate the nodule number and thus display a supernodulating phenotype. On studying the effect of pre-inoculation of one side of a split-root system with an arbuscular mycorrhizal fungus on subsequent mycorrhization in the second side of the split-root system of a wild-type soybean (Glycine max L.) cv. Bragg and its supernodulating mutant nts1007, we observed a clear suppressional effect in the wild-type, whereas further root colonization in the split-root system of the mutant nts1007 was not suppressed. These data strongly indicate that the mechanisms involved in supernodulation also affect mycorrhization and support the hypothesis that the autoregulation in the rhizobial and the mycorrhizal symbiosis is controlled in a similar manner. The accumulation patterns of the plant hormones IAA, ABA and Jasmonic acid (JA) in non-inoculated control plants and split-root systems of inoculated plants with one mycorrhizal side of the split-root system and one non-mycorrhizal side, indicate an involvement of IAA in the autoregulation of mycorrhization. Mycorrhizal colonization of soybeans also resulted in a strong induction of ABA and JA levels, but on the basis of our data the role of these two phytohormones in mycorrhizal autoregulation is questionable.
Publikation

Cenzano, A.; Vigliocc, A.; Miersch, O.; Abdala, G.; Hydroxylated jasmonate levels during stolon to tuber transition in Solarium tuberosum L Potato Res. 48, 107, (2005) DOI: 10.1007/BF02742370

Various octadecanoids and derived compounds have been identified in potato leaves. However, information regarding jasmonate hydroxylated forms in stolons or tubers is scarce. We investigated endogenous jasmonates in stolon material ofSolarium tuberosum cv. Spunta. Stolons and incipient tubers were collected from 8 weeks old plants. The material was cut into apical regions and stolons. We identified jasmonic acid (JA), methyl jasmonate, 11-OH-JA, 12-OH-JA, 12-oxo-phytodienoic acid (OPDA) and a conjugate. The content of JA and 12OH-JA decreased in the apical region but remained high in stolons during tuberization. Thus the apical region might be a site of JAs-utilization or metabolization and stolons might supply JAs to that region. The content of 12-OH-JA was higher than that of 11-OH-JA in all stages analyzed, both in apical regions and stolons. However, these compounds showed a different time-course in the apical region: while 11-OH-JA increased, 12-OH-JA decreased. Thus, JA from leaves or roots could be transported as 12-OH-JA to the apical region, stimulating tuber formation.
Publikation

Nibbe, M.; Hilpert, B.; Wasternack, C.; Miersch, O.; Apel, K.; Cell death and salicylate- and jasmonate-dependent stress responses in Arabidopsis are controlled by single cet genes Planta 216, 120-128, (2002) DOI: 10.1007/s00425-002-0907-1

The jasmonic acid (JA)-dependent regulation of the Thi2.1 gene had previously been exploited for setting up a genetic screen for the isolation of signal transduction mutants of Arabidopsis thaliana (L.) Heynh. that constitutively express the thionin gene. Several cet mutants had been isolated which showed a constitutive expression of the thionin gene. These cet mutants, except for one, also showed spontaneous leaf cell necrosis and were up-regulated in the expression of the PR1 gene, reactions often associated with the systemic acquired resistance (SAR) pathway. Four of these cet mutants, cet1, cet2, cet3 and cet4.1 were crossed with the fad triple and coi1 mutants that are blocked at two steps within the JA-dependent signaling pathway, and with transgenic NahG plants that are deficient in salicylic acid (SA) and are unable to activate SAR. Analysis of the various double-mutant lines revealed that the four cet genes act within a signaling cascade at or prior to branch points from which not only JA-dependent signals but also SA-dependent signaling and cell death pathways diverge.
Publikation

Görschen, E.; Dunaeva, M.; Hause, B.; Reeh, I.; Wasternack, C.; Parthier, B.; Expression of the ribosome-inactivating protein JIP60 from barley in transgenic tobacco leads to an abnormal phenotype and alterations on the level of translation Planta 202, 470-478, (1997) DOI: 10.1007/s004250050151

In this paper we report the in-planta activity of the ribosome-inactivating protein JIP60, a 60-kDa jasmonate-induced protein from barley (Hordeum vulgare L.), in transgenic tobacco (Nicotiana tabacum L.) plants. All plants expressing the complete JIP60 cDNA under the control of the cauliflower mosaic virus (CaMV) 35S promoter exhibited conspicuous and similar phenotypic alterations, such as slower growth, shorter internodes, lanceolate leaves, reduced root development, and premature senescence of leaves. Microscopic inspection of developing leaves showed a loss of residual meristems and higher degree of vacuolation of mesophyll cells as compared to the wild type. When probed with an antiserum which was immunoreactive against both the N- and the C-terminal half of JIP60, a polypeptide with a molecular mass of about 30 kDa, most probably a processed JIP60 product, could be detected. Phenotypic alterations could be correlated with the differences in the detectable amount of the JIP60 mRNA and processed JIP60 protein. The protein biosynthesis of the transformants was characterized by an increased polysome/monosome ratio but a decreased in-vivo translation activity. These findings suggest that JIP60 perturbs the translation machinery in planta. An immunohistological analysis using the JIP60 antiserum indicated that the immunoreactive polypeptide(s) are located mainly in the nucleus of transgenic tobacco leaf cells and to a minor extent in the cytoplasm.
Publikation

Feussner, I.; Hause, B.; Nellen, A.; Wasternack, C.; Kindl, H.; Lipid-body lipoxygenase is expressed in cotyledons during germination prior to other lipoxygenase forms Planta 198, 288-293, (1996) DOI: 10.1007/BF00206255

Lipid bodies are degraded during germination. Whereas some proteins, e.g. oleosins, are synthesized during the formation of lipid bodies of maturating seeds, a new set of proteins, including a specific form of lipoxygenase (LOX; EC 1.13.11.12), is detectable in lipid bodies during the stage of fat degradation in seed germination. In cotyledons of cucumber (Cucumis sativus L.) seedlings at day 4 of germination, the most conspicuous staining with anti-LOX antibodies was observed in the cytosol. At very early stages of germination, however, the LOX form present in large amounts and synthesized preferentially was the lipid-body LOX. This was demonstrated by immunocytochemical staining of cotyledons from 1-h and 24-h-old seedlings: the immunodecoration of sections of 24-h-old seedlings with anti-LOX antiserum showed label exclusively correlated with lipid bodies of around 3 μm in diameter. In accordance, the profile of LOX protein isolated from lipid bodies during various stages of germination showed a maximum at day 1. By measuring biosynthesis of the protein in vivo we demonstrated that the highest rates of synthesis of lipid-body LOX occurred at day 1 of germination. The early and selective appearance of a LOX form associated with lipid bodies at this stage of development is discussed.
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