Fungal elicitor stimulates a multicomponent defense response in cultured parsley cells (Petroselinum crispum). Early elements of this receptor-mediated response are ion fluxes across the plasma membrane and the production of reactive oxygen species (ROS), sequentially followed by defense gene activation and phytoalexin accumulation. Omission of Ca2+ from the culture medium or inhibition of elicitor-stimulated ion fluxes by ion channel blockers prevented the latter three reactions, all of which were triggered in the absence of elicitor by amphotericin B-induced ion fluxes. Inhibition of elicitor-stimulated ROS production using diphenylene iodonium blocked defense gene activation and phytoalexin accumulation. O2− but not H2O2 stimulated phytoalexin accumulation, without inducing proton fluxes. These results demonstrate a causal relationship between early and late reactions of parsley cells to the elicitor and indicate a sequence of signaling events from receptor-mediated activation of ion channels via ROS production and defense gene activation to phytoalexin synthesis. Within this sequence, O2− rather than H2O2 appears to trigger the subsequent reactions.

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A protein preparation from the mycelium of the tropical pathogenic fungus Botryodiplodia theobromae revealed a novel peptidase activity. This enzyme was capable of cleaving conjugates of jasmonic acid with α-amino acids. The protein was enriched 108-fold by gel filtration, ion exchange and hydrophobic interaction chromatography. The enzyme was found to be a glycoprotein with a molecular mass of about 107 kDa. The amidohydrolase seems to be very specific with regard to (−)-jasmonic acid and α-amino acids with (S)-configuration.

Diadenosine 5′,5′”‐P1,P4‐tetraphosphate (Ap4A) cleaving enzymes are assumed to regulate intracellular levels of Ap4A, a compound known to affect cell proliferation and stress responses. From plants an Ap4A hydrolase was recently purified using tomato cells grown in suspension. It was partially sequenced and a peptide antibody was prepared (Feussner et al., 1996). Using this polyclonal monospecific antibody, an abundant nuclear location of Ap4A hydrolase in 4‐day‐old cells of atomato cell suspension culture is demonstrated here by means of immunocytochemical techniques using FITC (fluorescein‐5‐isothiocyanate) labeled secondary antibodies. The microscopic analysis of the occurrence of Ap4A hydrolase performed for different stages of the cell cycle visualized by parallel DAPI (4,6‐diamidino‐2‐phenylindole) staining revealed that the protein accumulates within nuclei of cells in the interphase, but is absent in the nucleus as well as cytoplasm during all stages of mitosis. This first intracellular localization of an Ap4A degrading enzyme within the nucleus and its pattern of appearance during the cell cycle is discussed in relation to the suggested role of Ap4A in triggering DNA synthesis and cell proliferation.

We have studied a possible function of jasmonates as mediators in the host-pathogen interaction of barley (Hordeum vulgare L.) with the powdery mildew fungus Egh (Erysiphe graminis f. sp. hordei). Previous findings from whole-leaf extracts demonstrated that (i) extracts from infected barley leaves did not contain enhanced levels of jasmonates, (ii) transcripts of jasmonate-inducible genes were not expressed upon infection, and (iii) exogenous application of jasmonates did not induce resistance to Egh (Kogel et al., 1995). Nevertheless, the question arises whether or not jasmonates are involved in the interaction of barley with the powdery mildew fungus at the local site of infection. Using an immunocytological approach the analysis of leaf cross-sections from a susceptible barley cultivar and its near-isogenic mlo5-resistant line revealed no accumulation of JIP-23, the most abundant jasmonate inducible protein, neither in epidermal cells attacked by the pathogen nor in adjacent mesophyll cells. As a positive control, cross-sections from methyl jasmonate-treated leaf segments showed a strong signal for JIP-23 accumulation. Because the presence of the jasmonate-inducible protein is highly indicative for an already low threshold level of endogenous jasmonate (Lehmann et al., 1995), the lack of JIP-23 accumulation at the sites of attempted fungal infection clearly demonstrates the absence of enhanced levels of jasmonates. This excludes even a local rise of jasmonate confined to those single cells penetrated (Mlo genotype) or attacked (mlo5 genotype) by the fungus.

We investigated transgenic tobacco lines which express different amounts of the barley JIP 23. In these plants the amount of several proteins decreased proportionally to increasing amounts of JIP 23 whereas the transcript levels were constant as determined for the small and the large subunit of RuBPCase. However, the translation initiation of the rbcS transcript was found to be less efficient than in the wild type. In contrast, the jip 23 transcript was efficiently initiated, indicating that no unspecific impairment of initiation occurred. The data suggest that the barley JIP 23 leads to discrimination among certain tobacco transcripts during translation initiation.

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.

In a two step, one pot reaction of 4-benzyl oxazolidinone, 2-bromoacetyl halide, chromium dichloride and a suitable 3-oxo-aldehyde derivative the C1C6Me - fragment of epothilons is available in its correct oxidation state and enantiomeric form. Compared to common methods, the chromium-Reformatsky variation preferentially yields the opposite diastereomers and gives improved chemo- and diastereoselection.

anti-Aldol products are available in a two step, one pot reaction of 4-substituted oxazolidone, 2-bromopropionyl halide, chromium dichloride and an aldehyde. The diastereofacial selection (induction) is opposite to those of boron Evans enolates, i. e. the unusual “non-Evans” anto-aldol products are formed in excellent excess and yield - without base and at room temperature. In contrast to our previous assumptions α-unsubstituted acetyloxazolidones do give the Evans-type β-anti-products preferentially.

An efficient route for an alternative synthesis of gibberllin A1 from gibberellin A3 is described. Based on iodolactonisation the method provides access to gibberellin A1 labeled by deuterium with both high incorporation of the isotope and high stereoselectity at the positions 1β and 2α. The additional deuterium labeling at C‐17 was introduced via the corresponding 16‐norketone resulting in [1β,2α,17,17‐D4] gibberellin A1.