Rhizobium strain effects on pea: The relation between nitrogen accumulation, phosphoenolpyruvate carboxylase activity in nodules and asparagine in root bleeding sap

Pisum sativum L. cv. Bodil was infected with various strains of Rhizobium leguminosarum (R501, 128c53, B155, 18a or 1044). The Rhizobium genotype influenced the activity of the plant enzyme phosphoenoipyruvate (PEP) carboxylase (EC 4.1.1.31), and the assimilation of fixed N in the root nodules. The specific activity of nodule PEP carboxylase was lowest in the symbioses, which accumulated the least total N (R501 and 128c53). The root bleeding sap of the less effective symbioses contained a lower proportion of asparagine and a higher proportion of glutamine than the more effective symbioses (B155,18a and 1044). The N yield of the symbioses was related neither to the net respiratory CO₂ evolution of the root system nor to the nitrogenase linked nodule respiration. The lower yielding symbioses accumulated a larger proportion of the fixed N in the nodules due to a higher proportion of total dry weight contained in the nodule tissue. However, the concentration of soluble protein in the nodules of the lower-yielding symbioses was lower than that recorded for the higher yileding symbioses. The effect of the Rhizobium strains on N yield was maintained at maturity, and reflected in seed yields.     

Biochemical characterization of individual normal, floppy and rheumatic human mitral valves.

Human mitral valves (32 floppy and 17 rheumatic) obtained at surgery were analysed and compared with 35 normal (autopsy) valves. Total amounts of collagen, proteoglycan and elastin were increased approx. 3-fold in floppy and rheumatic valves. The water content of rheumatic cusps was lower than normal. The most significant changes in floppy valves were the 59% increase in mean value of the proteoglycan content, a large increase in the ease of extractability of proteoglycans from 26.7 to 57.2% of the total and a 62% increase in mean value of the elastin content in the anterior cusps. Normal human mitral valve cusps contained a mean proportion of 29.3 (and chordae 26.6) type III collagen (as % of total types III + I collagen), the values increasing significantly to 33.2 and 36.3% respectively in chronic rheumatic disease. The ratio observed in floppy valves depended on the extent of secondary surface fibrosis, which could be demonstrated histologically; in valve cusps with considerable secondary fibrosis, the percentage of type III increased significantly (to 34.4%), whereas it decreased significantly (to 25.2%) when fibrosis was negligible. It is concluded that the ratio of collagen types in floppy valves reflects the extent of secondary fibrosis rather than the pathogenesis of the disrupted collagen in the central core of the valve.     

Non-Decarboxylating transformation of indol-3-ylacetic acid in apple seeds

An enzyme extract from apple(Pyrus malus Borb.) seeds which causes the disappearance of free indol-3-ylacetic acid (IAA) requires the presence of oxygen, but is not inhibited by cyanide. Using 1-¹⁴C-IAA it has been demonstrated that the IAA transformation is not accompanied by its decarboxylation. Decarboxylating IAA oxidase is absent during the whole period of apple seed cold stratification. Free IAA has not been detected in dormant apple seeds and in seeds stratified at low temperature. It appears during stratification at 25 °C. Ethyl ester of IAA and indol-3-ylacetyl aspartate have been identified in dormant and after-ripened seeds. Exogenous 1-¹⁴C IAA taken up by apple embryos is converted into conjugates with aspartate and short peptides containing an aspartate moiety.     

The beta 1----2-D-xylose and alpha 1----3-L-fucose substituted N-linked oligosaccharides from Erythrina cristagalli lectin. Isolation, characterisation and comparison with other legume lectins

The carbohydrate moieties of Erythrina cristagalli lectin were released as oligosaccharides by hydrazinolysis, followed by N-acetylation and reduction with NaB3H4. Fractionation of the tritium-labelled oligosaccharide mixture by Bio-Gel P-4 column chromatography and high-voltage borate electrophoresis revealed that it is composed of five neutral oligosaccharides. Structural studies by sequential exoglycosidase digestion in combination with methylation analysis and two-dimensional 1H-NMR showed that the major component was the fucose-containing heptasaccharide Man alpha 3(Man alpha 6)(Xyl beta 2)Man beta 4GlcNAc beta 4(Fuc alpha 3)GlcNAcol. This is the first report of such a structure in plant lectins. Small amounts of the corresponding afucosyl hexasaccharide were also identified, as well as three other minor components. The structure of the heptasaccharide shows the twin characteristics of a newly established family of N-linked glycans, found to date only in plants. The characteristics are substitution of the common pentasaccharide core [Man alpha 3(Man alpha 6)Man beta 4GlcNAc beta 4GlcNAc] by a D-xylose residue linked beta 1----2 to the beta-mannosyl residue and an L-fucose residue linked alpha 1----3 to the reducing terminal N-acetylglucosamine residue. The oligosaccharide heterogeneity pattern for Erythrina cristagalli lectin was also found for the lectins from four other Erythrina species and the lectins of two other legumes, Sophora japonica and Lonchocarpus capassa.     

Binding and precipitating activities ofErythrina lectins with complex type carbohydrates and synthetic cluster glycosides. A comparative study of the lectins fromE. corallodendron,E. cristagalli,E. flabelliformis,andE. indica

Erythrina lectins possess similar structural and carbohydrate binding properties. Recently, tri- and tetra-antennary complex type carbohydrates with non-reducing terminal galactose residues have been shown to be precipitated as tri- and tetravalent ligands, respectively, with certainErythrina lectins [Bhattacharyya L, Haraldsson M, Brewer CF (1988) Biochemistry 271034-41]. The present work describes a comparative study of the binding and precipitating activities of fourErythrina lectins,viz. E. corallodendron, E. cristagalli, E. flabelliformis, andE. indica, with multi-antennary complex type carbohydrates and synthetic cluster glycosides. The results show that though their binding affinities are very similar, theErythrina lectins show large differences in their precipitating activities with the carbohydrates. The results also indicate significant dependence of the precipitating activities of the lectins on the core structure of the carbohydrates. These findings provide a new dimension to the structure-activity relationship of the lectins and their interactions with asparagine-linked carbohydrates.Abbreviations EAL, ECorL, ECL, EFL, and EIL represent the lectins from the seeds ofErythrina arborescens, - E. corallodendron, E. cristagalli, E. flabelliformis, andE. indica respectively - AFOS thetri-antennary complex type oligosaccharide from asialofetuin - AFGP the tri-antennary glycopeptide from asialofetuin - MeGal methyl -d-galactopyranoside Unless stated otherwise all sugars are in thed-configuration.     

Physiological levels of diacylglycerols in phospholipid membranes induce membrane fusion and stabilize inverted phases

In the preceding paper (Ellens et al., 1989), it was shown that liposome fusion rates are substantially enhanced under the same conditions which induce isotropic 31P NMR resonances in multilamellar dispersions of the same lipid. Both of these phenomena occur within the same temperature interval, delta TI, below the L alpha/HII phase transition temperature, TH. TH and delta TI can be extremely sensitive to the lipid composition. The present work shows that 2 mol% of diacylglycerols like those produced by the phosphatidylinositol cycle in vivo can lower TH, delta TI, and the temperature for fast membrane fusion by 15-20 degrees C. N-Monomethylated dioleoylphosphatidylethanolamine is used as a model system. These results show that physiological levels of diacylglycerols can substantially increase the susceptibility of phospholipid membranes to fusion. This suggests that, in addition to their role in protein kinase C activation, diacylglycerols could play a more direct role in the fusion event during stimulus-exocytosis coupling in vivo.     

Structure and expression of ubiquitin genes of Drosophila melanogaster.

We isolated and characterized two related ubiquitin genes from Drosophila melanogaster, polyubiquitin and UB3-D. The polyubiquitin gene contained 18 repeats of the 228-base-pair monomeric ubiquitin-encoding unit arranged in tandem. This gene was localized to a minor heat shock puff site, 63F, and it encoded a constitutively expressed 4.4-kilobase polyubiquitin-encoding mRNA, whose level was induced threefold by heat shock. To investigate the pattern of expression of the polyubiquitin gene in developing animals, a polyubiquitin-lacZ fusion gene was introduced into the Drosophila genome by germ line transformation. The fusion gene was expressed at high levels in a tissue-general manner at all life stages assayed. The ubiquitin-encoding gene, UB3-D, consisted of one ubiquitin-encoding unit directly fused, in frame, to a nonhomologous tail sequence. The amino acid sequence of the tail portion of the protein had 65% positional identity with that of yeast UBI3 protein, including a region that contained a potential nucleic acid-binding motif. The Drosophila UB3-D gene hybridized to a 0.9-kilobase mRNA that was constitutively expressed, and in contrast to the polyubiquitin gene, it was not inducible by heat shock.     

Hydrogen cyanide and embryonal dormancy in apple seeds

Embryos of apple ( Malus domestica Borh. cv. Antonówka) were treated with 1 m M gaseous HCN for 6 h and cultured under a 12 h photoperiod. HCN pretreatment stimulated germination, increased the length of hypocotyls, shortened the main root and decreased the percentages of seedlings with asymmetrically grown as well as with asymmetrically greened cotyledons. High activity of β-cyanoalanine synthase (EC 4.4.1.9) and a sharp increase in cyanogen content during embryo culture suggested very low levels of endogenous HCN. despite the activity of HCN releasing enzymes. The obtained data allow us to postulate an important role for cyanide in the regulatory complex controlling dormancy in apple seeds. Experiments with respiratory inhibitors indicated, however, that HCN pretreatment affected neither the alternative electron transport pathway nor residual respiration.