Die Karpelle vonEranthis hiemalis undCimicifuga americana als weitere Verbindungsglieder zwischen peltaten und epeltaten Karpellen

Zusammenfassung Die Karpelle vonEranthis hiemalis undCimicifuga americana vermitteln den Übergang zwischen den peltaten und den epeltaten Karpellen, da ihre Querzone nicht mehr wie bei den peltaten Karpellen im Spreitenbereich liegt und noch nicht wie bei den epeltaten Karpellen gänzlich unterdrückt ist, sondern sich intermediär verhält, nämlich in den Karpellstiel verlagert ist. Die bei ihnen also auffallend tiefe Lage der Querzone erweist sich als eine Folge der späten Querzonenanlegung.Ähnliche Verhältnisse wurden bisher nur vonGrevillea Thelemanniana bekannt.     

Construction ofClostridium butyricum hybrid plasmids and transfer toBacillus subtilis

Summary Small plasmids were isolated from type strains ofClostridium butyricum. Strain NCIB 7423 carries one plasmid (pCBU1) of 6.4 kb, whereas strain NCTC 7423 carries two unrelated plasmids of 6.3 kb (pCBU2) and 8.4 kb (pCBU3). Cleavage sites for 18 restriction endonucleases have been mapped on these plasmids and detailed physical maps are presented. For the purpose of developing vector plasmids for gene cloning in saccharolytic clostridia these crypticC. butyricum plasmids were joined to a selectable marker that will likely be expressed in clostridia. This was achieved by cloning the clostridial plasmids into theE. coli vector pBR322 carrying the chloramphenicol acetyltransferase (CAT) gene from theStaphylococcus aureus plasmid pC194. The recombinant plasmids were tested for their ability to confer chloramphenicol resistance toBacillus subtilis. Hybrid plasmids (pHL105, pHL1051) derived from pCBU2 were identified, which are capable of replication and expression of theS. aureus drug resistance marker in bothE. coli andB. subtilis. No structural instability was detected upon retransformation of pHL105 fromB. subtilis intoE. coli. The recombinant plasmids might thus be useful as shuttle vectors for the gene transfer betweenE. coli and a wide range of bacilli and clostridia.     

Bioguided Fractionation and Isolation of an Antiplasmodial Saponin from the Roots of Nauclea xanthoxylon (A.Chev.) Aubrév. (Rubiaceae)

The root extract of Nauclea xanthoxylon (A.Chev.) Aubrév. displayed significant 50 % inhibition concentration (IC₅₀s) of 0.57 and 1.26 μg/mL against chloroquine resistant and sensitive Plasmodium falciparum (Pf) Dd2 and 3D7 strains, respectively. Bio-guided fractionation led to an ethyl acetate fraction with IC₅₀s of 2.68 and 1.85 μg/mL and subsequently, to the new quinovic acid saponin named xanthoxyloside ( 1 ) with IC₅₀s of 0.33 and 1.30 μM, respectively against the tested strains. Further compounds obtained from ethyl acetate and hexane fractions were the known clethric acid ( 2 ), ursolic acid ( 3 ), quafrinoic acid ( 4 ), quinovic acid ( 5 ), quinovic acid 3-O-β-D-fucopyranoside ( 6 ), oleanolic acid ( 7 ), oleanolic acid 3-acetate ( 8 ), friedelin ( 9 ), β-sitosterol ( 10a ), stigmasterol ( 10b ) and stigmasterol 3-O-β-D-glucopyranoside ( 11 ). Their structures were characterised with the aid of comprehensive spectroscopic methods (1 and 2D NMR, Mass). Bio-assays were performed using nucleic acid gel stain (SYBR green I)-based fluorescence assay with chloroquine as reference. Extracts and compounds exhibited good selectivity indices (SIs) of >10. Significant antiplasmodial activities measured for the crude extract, the ethyl acetate fraction and xanthoxyloside ( 1 ) from that fraction can justify the use of the root of N. xanthoxylon in ethnomedicine to treat malaria.     

The growth of Saccharomyces cerevisiae CBS 426 on mixtures of glucose and ethanol: a model

Saccharomyces cerevisiae CBS 426 was grown in continuous culture in a defined medium with a mixture of glucose and ethanol as carbon source. Growth on ethanol as the sole carbon source was only possible after the addition of a small amount of glutamic acid. The flows of glucose, ethanol, oxygen, carbon dioxide and biomass to and from the system were measured and a model for the growth of the yeast on the carbon sources constructed. The model is shown to allow independent estimation of Y_ATP and P/O. Y_ATP is not independent of the substrate used, but the amount of ATP used in the production of biomass from the monomers is approximately the same for growth on ethanol and on glucose.Nomenclature C chemical state vector - C_i component of the chemical state vector (C-mol) - C_x biomass present in the system (C-mol biomass) - H₂ reduction equivalents (NAD(P)H + H⁺ and FADH₂) - k the amount of ATP required in the production of 1 C-mol of biomass from the monomers (mol ATP/C-mol biomass) - m_ATP maintenance requirement for ATP (mol ATP/C-mol biomass·h) - P/O (=), efficiency of the oxidative phosphorylation (mol ATP/atom O) - r vector of reaction rates - r_i component of the vector of reaction rates (C-mol/h) - r_ATP rate of ATP production (mol ATP/h) - r_x rate of biomass production (C-mol biomass/h) - Y_ATP Y_ATP growth yield on ATP (C-mol biomass/mol ATP) - (Y_ATP)_max maximum growth yield on ATP - stoichiometry matrix - P/O - vector of the flows to the system - _s flow of glucose to the system (C-mol glucose/h) - _o flow of oxygen to the system (mol O₂/h) - _c flow of carbon dioxide to the system (mol CO₂/h) - _x flow of biomass to the system (C-mol biomass/h) - _e flow of ethanol to the system (C-mol ethanol/h) - _w flow of water produced during metabolism (mol H₂O/h)     

When History Repeats Itself: Exploring the Genetic Architecture of Host-Plant Adaptation in Two Closely Related Lepidopteran Species

The genus Ostrinia includes two allopatric maize pests across Eurasia, namely the European corn borer (ECB, O. nubilalis) and the Asian corn borer (ACB, O. furnacalis). A third species, the Adzuki bean borer (ABB, O. scapulalis), occurs in sympatry with both the ECB and the ACB. The ABB mostly feeds on native dicots, which probably correspond to the ancestral host plant type for the genus Ostrinia. This situation offers the opportunity to characterize the two presumably independent adaptations or preadaptations to maize that occurred in the ECB and ACB. In the present study, we aimed at deciphering the genetic architecture of these two adaptations to maize, a monocot host plant recently introduced into Eurasia. To this end, we performed a genome scan analysis based on 684 AFLP markers in 12 populations of ECB, ACB and ABB. We detected 2 outlier AFLP loci when comparing French populations of the ECB and ABB, and 9 outliers when comparing Chinese populations of the ACB and ABB. These outliers were different in both countries, and we found no evidence of linkage disequilibrium between any two of them. These results suggest that adaptation or preadaptation to maize relies on a different genetic architecture in the ECB and ACB. However, this conclusion must be considered in light of the constraints inherent to genome scan approaches and of the intricate evolution of adaptation and reproductive isolation in the Ostrinia spp. complex.     

Diazaborine treatment of yeast cells inhibits maturation of the 60S ribosomal subunit

Diazaborine treatment of yeast cells was shown previously to cause accumulation of aberrant, 3'-elongated mRNAs. Here we demonstrate that the drug inhibits maturation of rRNAs for the large ribosomal subunit. Pulse-chase analyses showed that the processing of the 27S pre-rRNA to consecutive species was blocked in the drug-treated wild-type strain. The steady-state level of the 7S pre-rRNA was clearly reduced after short-term treatment with the inhibitor. At the same time an increase of the 35S pre-rRNA was observed. Longer incubation with the inhibitor resulted in a decrease of the 27S precursor. Primer extension assays showed that an early step in 27S pre-rRNA processing is inhibited, which results in an accumulation of the 27SA2 pre-rRNA and a strong decrease of the 27SA3, 27SB1L, and 27SB1S precursors. The rRNA processing pattern observed after diazaborine treatment resembles that reported after depletion of the RNA binding protein Nop4p/Nop77p. This protein is essential for correct pre-27S rRNA processing. Using a green fluorescent protein-Nop4 fusion, we found that diazaborine treatment causes, within minutes, a rapid redistribution of the protein from the nucleolus to the periphery of the nucleus, which provides a possible explanation for the effect of diazaborine on rRNA processing.     

Rational engineering of a fluorescein-binding anticalin for improved ligand affinity

The anticalin FluA is an artificial lipocalin with novelspecificity for the fluorescein group, which was engineered from an insect bilin-binding protein by targeted random mutagenesis and selection. Based on the crystal structure of FluA, an attempt was made to improve the complementarity of its ligand pocket to fluorescein by rational protein design. Several side chains participating in sub-optimal interactions with the ligand were identified and replaced by residues that promised a better steric fit. As a result, the substitution of Ala45 by Ile and of Ser114 by Thr or Arg led to a tight affinity of ca. 1 nM, which is approximately 30-fold better than that of the parental anticalin. Similar to the original FluA, the improved version shows almost complete quenching of the bound ligand fluorescence. Interestingly, the quenching effect was significantly reduced when Trp129 was replaced by Tyr, thus supporting the previously postulated role of this residue, which closely packs against the bound ligand, for efficient electron transfer to the excited fluorescein. Circular dichroism spectra revealed that all variants investigated had retained the lipocalin fold. Corresponding thermal unfolding experiments confirmed similar folding stabilities, with melting temperatures ranging from 52.9 to 60.5 degrees C (i.e., for the high-affinity variant).