Aus der Frühgeschichte des Verbandes Deutscher Zoodirektoren (VDZ) e.V. – Aus den Archiven des Zoologischen Gartens Breslau/Wrocław

The early history of the VDZ is nearly unknown. Surprisingly many historical materials of great value were discovered while reorganizing the library and archives of Wroc?aw (Breslau) Zoo. One of these discoveries is the nearly full set of the minutes from the meetings of the directors of German zoos starting from the first meeting in 1887 up to the 41st meeting held in 1929. To fill in the gap of the knowlegde about the history of VDZ we give a list of the meetings with some citations of each minutes. The full and complete list of all the meetings from the years 1887 – 1929 is given, with the dates, place and list of the participants. All names, titles and numeration cited here are exactly as printed in the original minutes. Also the citations, randomly derived from the minutes are given here exactly as in the original minutes.     

Monoterpene biosynthesis in lemon (Citrus limon). cDNA isolation and functional analysis of four monoterpene synthases.

Citrus limon possesses a high content and large variety of monoterpenoids, especially in the glands of the fruit flavedo. The genes responsible for the production of these monoterpenes have never been isolated. By applying a random sequencing approach to a cDNA library from mRNA isolated from the peel of young developing fruit, four monoterpene synthase cDNAs were isolated that appear to be new members of the previously reported tpsb family. Based on sequence homology and phylogenetic analysis, these sequences cluster in two separate groups. All four cDNAs could be functionally expressed in Escherichia coli after removal of their plastid targeting signals. The main products of the enzymes in assays with geranyl diphosphate as substrate were (+)-limonene (two cDNAs) (-)-beta-pinene and gamma-terpinene. All enzymes exhibited a pH optimum around 7; addition of Mn(2+) as bivalent metal ion cofactor resulted in higher activity than Mg(2+), with an optimum concentration of 0.6 mm. K(m) values ranged from 0.7 to 3.1 microm. The four enzymes account for the production of 10 out of the 17 monoterpene skeletons commonly observed in lemon peel oil, corresponding to more than 90% of the main components present.     

Volatile science? Metabolic engineering of terpenoids in plants

Terpenoids are important for plant survival and also possess biological properties that are beneficial to humans. Here, we describe the state of the art in terpenoid metabolic engineering, showing that significant progress has been made over the past few years. Subcellular targeting of enzymes has demonstrated that terpenoid precursors in subcellular compartments are not as strictly separated as previously thought and that multistep pathway engineering is feasible, even across cell compartments. These engineered plants show that insect behavior is influenced by terpenoids. In the future, we expect rapid progress in the engineering of terpenoid production in plants. In addition to commercial applications, such transgenic plants should increase our understanding of the biological relevance of these volatile secondary metabolites.     

Functional characterization of enzymes forming volatile esters from strawberry and banana

Volatile esters are flavor components of the majority of fruits. The last step in their biosynthesis is catalyzed by alcohol acyltransferases (AATs), which link alcohols to acyl moieties. Full-length cDNAs putatively encoding AATs were isolated from fruit of wild strawberry (Fragaria vesca) and banana (Musa sapientum) and compared to the previously isolated SAAT gene from the cultivated strawberry (Fragaria x ananassa). The potential role of these enzymes in fruit flavor formation was assessed. To this end, recombinant enzymes were produced in Escherichia coli, and their activities were analyzed for a variety of alcohol and acyl-CoA substrates. When the results of these activity assays were compared to a phylogenetic analysis of the various members of the acyltransferase family, it was clear that substrate preference could not be predicted on the basis of sequence similarity. In addition, the substrate preference of recombinant enzymes was not necessarily reflected in the representation of esters in the corresponding fruit volatile profiles. This suggests that the specific profile of a given fruit species is to a significant extent determined by the supply of precursors. To study the in planta activity of an alcohol acyltransferase and to assess the potential for metabolic engineering of ester production, we generated transgenic petunia (Petunia hybrida) plants overexpressing the SAAT gene. While the expression of SAAT and the activity of the corresponding enzyme were readily detected in transgenic plants, the volatile profile was found to be unaltered. Feeding of isoamyl alcohol to explants of transgenic lines resulted in the emission of the corresponding acetyl ester. This confirmed that the availability of alcohol substrates is an important parameter to consider when engineering volatile ester formation in plants.     

Circadian rhythmicity in emission of volatile compounds by flowers of Rosa hybrida L. cv. Honesty

Quantitative headspace analyses of rose flowers showed no significant differences in composition of emitted volatile compounds between flowers on the intact plant and cut flowers placed in vase water containing sucrose at 0, 15 or 30 g · l⁻¹. Volatile components emitted were geraniol, nerol, citronellol, E-citral, Z-citral, methylgeranylate, trans-caryophyllene, β-cubebene, dihydro-β-ionone, 2-phenylethanol, 2-phenylethylacetate, 3,5-dimethoxytoluene and hexylacetate. When exposed to a 12-h photoperiod these components showed maximum emission during the light period and a rhythmicity which differed for the individual compounds. The circadian nature of the rhythmicity was confirmed by the continuation of rhythmicity during continued darkness or light, and was characterized by `transient' and `free running' periods of 27 and 24 h, respectively, and a phase shift of 12 h in rhythmicity when a 24-h period of continuous darkness was followed by re-exposure to a 12-h photoperiod. Rhythmicity in emission was not observed when flowers were kept in darkness before flower bud opening, but started immediately upon exposure to a 12-h photoperiod. Received: 14 April 1998 / Accepted: 28 May 1998     

Electric surface charge dynamics of chloroplast thylakoid membranes. Temperature dependence of electrokinetic potential and aminoacridine interaction

Electric surface charge dynamics of unstacked broken chloroplasts at low-ionic strength were studied by free-flow electrophoresis and aminoacridine fluorescence and binding changes over the temperature range 4–36°C. Both illumination and ATP hydrolysis in the dark cause a significant increase of net negative surface charge. The light and dark electrokinetic (ζ) potentials have a broad temperature optimum between 20 and 36°C. The decline at lower temperature shows a transition at about 18°C. The ATP-induced increase of the ζ potential requires preactivation of the ATPase and is dicyclohexylcarbodiimide sensitive. Aminoacridine binding shows a quite different temperature dependence. At lower temperatures there is an increased number of binding sites with a decreased affinity and the binding becomes positively cooperative. It is demonstrated that aminoacridines aggregate to dimers upon binding to the membranes. This phenomenon is stimulated by light and favoured at lower temperatures. The light-dependent extra binding increases sigmoidally with increasing temperature, similar to the increase of ζ potential, but with a less abrupt transition. The different effects of temperature on the electrokinetic and binding data are explained in terms of surface charge screening in the electric double-layer of the thylakoid membrane.     

Isoprenoid biosynthesis in Artemisia annua: cloning and heterologous expression of a germacrene A synthase from a glandular trichome cDNA library

Artemisia annua (Asteraceae) is the source of the anti-malarial compound artemisinin. To elucidate the biosynthetic pathway and to isolate and characterize genes involved in the biosynthesis of terpenoids including artemisinin in A. annua, glandular trichomes were used as an enriched source for biochemical and molecular biological studies. The sequencing of 900 randomly selected clones from a glandular trichome plasmid cDNA library revealed the presence of many ESTs involved in isoprenoid biosynthesis such as enzymes from the methylerythritol phosphate pathway and the mevalonate pathway, amorpha-4,11-diene synthase and other sesquiterpene synthases, monoterpene synthases and two cDNAs showing high similarity to germacrene A synthases. Full-length sequencing of the latter two ESTs resulted in a 1686-bp ORF encoding a protein of 562 aa. Upon expression in Escherichia coli, the recombinant protein was inactive with geranyl diphosphate, but catalyzed the cyclization of farnesyl diphosphate to germacrene A. These results demonstrate the potential of the use of A. annua glandular trichomes as a starting material for studying isoprenoid biosynthesis in this plant species.     

Tomato strigolactones: A more detailed look

Strigolactones are plant signaling molecules that induce germination of parasitic plant seeds, initiate host plant - arbuscular mycorrhizal fungus symbiosis and act as plant hormones controlling shoot branching and root architecture. To date four unique strigolactones (e.g., orobanchol, didehydroorobanchol isomers 1 and 2 and the aromatic strigolactone solanacol) have been reported in the root exudates and extracts of tomato (Solanum lycopersicum). Here we report on the presence of several additional strigolactones in tomato root exudates and extracts, orobanchyl acetate, two 7-hydroxyorobanchol isomers, 7-oxoorobanchol and two additional didehydroorobanchol isomers and discuss their possible biological relevance.     

Gene Coexpression Analysis Reveals Complex Metabolism of the Monoterpene Alcohol Linalool in Arabidopsis Flowers

The cytochrome P450 family encompasses the largest family of enzymes in plant metabolism, and the functions of many of its members in Arabidopsis thaliana are still unknown. Gene coexpression analysis pointed to two P450s that were coexpressed with two monoterpene synthases in flowers and were thus predicted to be involved in monoterpenoid metabolism. We show that all four selected genes, the two terpene synthases (TPS10 and TPS14) and the two cytochrome P450s (CYP71B31 and CYP76C3), are simultaneously expressed at anthesis, mainly in upper anther filaments and in petals. Upon transient expression in Nicotiana benthamiana, the TPS enzymes colocalize in vesicular structures associated with the plastid surface, whereas the P450 proteins were detected in the endoplasmic reticulum. Whether they were expressed in Saccharomyces cerevisiae or in N. benthamiana, the TPS enzymes formed two different enantiomers of linalool: (−)-(R)-linalool for TPS10 and (+)-(S)-linalool for TPS14. Both P450 enzymes metabolize the two linalool enantiomers to form different but overlapping sets of hydroxylated or epoxidized products. These oxygenated products are not emitted into the floral headspace, but accumulate in floral tissues as further converted or conjugated metabolites. This work reveals complex linalool metabolism in Arabidopsis flowers, the ecological role of which remains to be determined.