Ethanol utilization regulatory protein: profile alignments give no evidence of origin through aldehyde and alcohol dehydrogenase gene fusion.

The suggestion that the ethanol regulatory protein from Aspergillus has its evolutionary origin in a gene fusion between aldehyde and alcohol dehydrogenase genes (Hawkins AR, Lamb HK, Radford A, Moore JD, 1994, Gene 146:145-158) has been tested by profile analysis with aldehyde and alcohol dehydrogenase family profiles. We show that the degree and kind of similarity observed between these profiles and the ethanol regulatory protein sequence is that expected from random sequences of the same composition. This level of similarity fails to support the suggested gene fusion.     

Etude olfactométrique de l'action de diverses substances allélochimiques végétales dans la recherche de l'hote par Diadromus pulchellus (Hymenoptera,Ichneumonidae)

Résumé La recherche de l'habitat d'un hôte potentiel par D. pulchellus, endoparasite considéré comme spécialiste des nymphes d'A. assectella, est abordée chez les adultes femelles et mâles, en olfactométrie, par l'étude de leur comportement locomoteur. L'activité locomotrice et l'attraction sont ainsi analysées en présence de substances allélochimiques issues ou non de végétaux pouvant abriter un hôte. Que les composés soufrés testés soient stables ou non, ils ne déclenchent pas d'attraction chez les hyménoptères quel que soit leur sexe et le type d'olfactomètre utilisé, contrairement aux imagos du phytophage-hôte, A. assectella, attirés par les composés soufrés instables spécifiques du poireau. L'activité locomotrice des hyménoptères des deux sexes est stimulée par divers composés volatils soufrés de synthèse ou émis naturellement par les Crucifères et par les Allium consommés par les larves d'A. assectella. Les substances efficaces sont généralément stables et sont caractérisées par le groupement actif R-S-, à condition que R ne soit pas un allyle. Par ailleurs, des composés volatils non soufrés contenus dans des végétaux autres que les Allium et les Crucifères ne stimulent pas le comportement locomoteur des hyménoptères. Ces différentes observations permettent d'envisager que D. pulchellus est un spécialiste inféodé à des microlépidoptères s'alimentant sur des végétaux soufrés et non sur les seuls Allium.

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Summary Searching the host habitat by the endoparasite wasp Diadromus pulchellus, considered to be a specialist of Acrolepiopsis assectella nymphs, is studied in females and males by analysis of locomotory behaviour in olfactometers. Thus, locomotor activity and attraction are studied in the presence or absence of air-borne volatiles emitted by plants able to shelter a potential host-moth. Stable and unstable sulphur compounds used do not release attraction in female and male ichneumonids whatever the type of olfactometer used. By contrast, phytophagous host adults are attracted by unstable specific sulphur compounds of the leek. Locomotor activities of D. pulchellus females and males are stimulated by various volatile sulphur compounds of synthetic origin or naturally occurring in Allium eaten by A. assectella larvae and in Crucifera. The effective compounds generally are stable and characterized by the active group R-S — in which the alkyl moiety must not be an allyl one. On the other hand, volatiles without sulphur, emitted by plants which do not belong to Cruciferae or Allium, do not stimulate the hymenopteran locomotor activity. These observations suggest that D. pulchellus is oligophagous, attracted to microlepidoptera developing on plants containing sulphur compounds and not only on Allium.

     

Polysaccharide and oligosaccharide changes in germinating lupin cotyledons

In germinating lupin cotyledons, there was a rapid depletion of raffinose series oligosaccharides, a temporary increase in sucrose and constant low levels of reducing monosaccharides. The major polysaccharide fraction was extracted with hot NH₄ oxalate—EDTA solution and had the constitution of intercellular/cell wall polysaccharide. GLC examination of component sugars showed that as cotyledons expanded this fraction was depleted and that there was selective hydrolysis of arabinose and galactose, so that the uronic acid proportion increased. Gel and DEAE-cellulose chromatography showed that this fraction became more heterogeneous. The neutral and acidic fractions were separated and the component sugars, viscosities, gel chromatographic behaviour and sedimentation constants of these determined. The results indicated that in the later phase of plant cell wall expansion in germinating lupin cotyledons the arabinogalactan side chains of the pectic polysaccharide fraction are selectively hydrolysed leaving a primary wall with a high uronic acid content.     

Isolation and characterization of wheat peroxidase isoenzyme B1

Two pure peroxidase isoenzymes B1 and D4 were isolated from the upper parts of 10-day-old wheat seedlings by means of gel and ion-exchange chromatography. Their MWs were 85000 and 24000 respectively. B1 was unstable and under various conditions it was converted to another isoenzyme, electrophoretically identical with D4. B1 contains about 40% of neutral sugars: 17.2% arabinose, 15.3% galactose, 5% glucose and traces of mannose. D4 is free of neutral sugars. None of the isoenzymes contained amino sugars. B1 oxidizes ferulic and p-coumaric acids. This oxidation has two pH optima of 4.4 and 5.4–5.6 and is inhibited by high concentrations of substrates, cyanide and azide. B1 oxidizes IAA in the presence of phenolic cofactor and Mn²⁺ ions. IAA oxidation has two pH optima of 4.5 and 5.6 and is inhibited by high substrate concentration, cyanide and azide, and by a number of indole derivatives. The main products of IAA oxidation are 3-methyleneoxindole and indole-3-methanol. o- and p- diphenols induce a lag period prior to IAA oxidation. Ferulic acid is oxidized during this lag period, probably to a dimer. B1 is able to produce H₂O₂ from oxygen. Mn²⁺ ions, a phenolic cofactor and an electron donor (IAA or NADH) are needed. B1 oxidizes α-keto-γ- methylmercaptobutyric acid to ethylene. D4 has a low peroxidatic activity and is inactive as an IAA oxidase. Thus B1 is probably an active cell wall-bound peroxidase isoenzyme, whereas D4 is its decomposition product.     

Dihydropyridine Modulation of Voltage-Activated Calcium Channels in PC12 Cells: Effect of Pertussis Toxin Pretreatment

In this study, we report the effect of pertussis toxin pretreatment on dihydropyridine modulation of voltage-sensitive calcium channels in PC12 cells. The rise in intracellular calcium concentration caused by potassium depolarization is not affected significantly by pertussis toxin pretreatment. Nicardipine, a dihydropyridine derivative, added either before or after potassium-induced depolarization, reduces the resultant elevation in cytosolic calcium level both in control and in pertussis toxin-treated cells. The dihydropyridine agonist Bay K 8644, when added before potassium, is able to enhance the potassium-induced spike of cytosolic calcium levels, an effect significantly reduced by pertussis toxin pretreatment. Moreover, the addition of Bay K 8644 after potassium holds the intracellular calcium concentration at a cytosolic sustained level during the slow inactivating phase of depolarization. This effect of Bay K 8644 is inhibited by nicardipine. Pertussis toxin pretreatment slightly weakens the effect of Bay K 8644 when added after potassium-induced depolarization, whereas it significantly reduces the nicardipine inhibition of cytosolic calcium rise stimulated by potassium and Bay K 8644, but not by potassium alone. In conclusion, our findings suggest that a pertussis toxin-sensitive guanine nucleotide regulatory protein could be involved in the interaction between dihydropyridine derivatives and voltage-dependent calcium channels.     

Escherichia coli leucine-responsive regulatory protein (Lrp) controls lysyl-tRNA synthetase expression

Using random Tn10 insertion mutagenesis, we isolated an Escherichia coli mutant strain affected in the regulation of lysU, the gene encoding the inducible form of lysyl-tRNA synthetase. The transposon giving rise to the altered expression of lysU was found inserted within lrp. The latter gene codes for the leucine-responsive regulatory protein (Lrp) which mediates a global response of the bacterium to leucine. An involvement of Lrp in the regulation of lysU was searched for by using a lysU-lacZ operon fusion. The following conclusions were reached: (i) inactivation of lrp causes an increased activity of the lysU promoter, whatever the growth conditions assayed, (ii) insertion of a wild-type lrp gene into a multi-copy plasmid significantly reduces lysU expression, and (iii) sensitivity of the lysU promoter to the presence of leucine in the growth medium is abolished in the lrp context.     

Tryptophan-dependent biosynthesis of auxins in soil

The presence of auxins in soil may have an ecological impact affecting plant growth and development. A rapid and simple colorimetric method was used to assess California soils for their potential to produce auxins upon the addition of L-tryptophan (L-TRP). The auxin content measured by colorimetry was expressed as indole-3-acetic acid (IAA)-equivalents. A substrate (L-TRP) concentration of 5.3 g kg^-1, glucose concentration of 6.7 g kg^-1, no nitrogen, pH 7.0, 40°C, shaking (aeration) and 48 h incubation time were selected as standardized conditions to assay for auxin biosynthesis in soil. IAA was confirmed as a major microbial metabolite derived from L-TRP in soil by use of high performance liquid chromatography (HPLC). Under standardized conditions, L-TRP-derived auxins in 19 soils varied greatly ranging from 18.2 to 303.2 mg IAA equivalents (auxins) kg^-1 soil. This study suggests that the phenotypic character of the soil microbiota has more of an influence on auxin production than the soil physicochemical properties (e.g., pH, organic C content, CEC, etc.).     

Lectin cell adhesion molecules (LEC-CAMs): a new family of cell adhesion proteins involved with inflammation.

The means by which leukocytes, including lymphocytes, monocytes, and neutrophils, migrate from the circulation to sites of acute and chronic inflammation is an area of intense research interest. Although a number of soluble mediators of these important cellular interactions have been identified, a major site of great importance to the inflammatory response is the physical interface between the white cell and the endothelium. This critical association is mediated by an array of cell surface adhesion molecules. Previous data have demonstrated that the integrin subfamily of heterotypic adhesion molecules was a major component of these adhesive interactions, although it was clear that other, non-integrin-like molecules of unknown identity also seemed to be involved during the inflammatory process. A number of these other cell-surface glycoproteins which may be involved with inflammation have recently been characterized by molecular cloning. These glycoproteins, including the peripheral lymph node homing receptor (pln HR), the endothelial cell adhesion molecule (ELAM), and PADGEM/gmp140, are all members of a family of proteins which are unified by the inclusion of three characteristic protein motifs: a lectin or carbohydrate recognition domain, an epidermal growth factor (egf) domain, and a variable number of short consensus repeats (scr) which are also found in members of the complement regulatory proteins. The appearance of lectin domains in all of these adhesion molecules is consistent with the possibility that these glycoproteins function by binding to carbohydrates which are expressed in a cell and/or region specific manner, and the members of this adhesion family have been given the generic name LEC-CAM (lectin cell adhesion molecules).(ABSTRACT TRUNCATED AT 250 WORDS)