Plant fructans stabilize phosphatidylcholine liposomes during freeze-drying. (1/73)

Fructans have been implicated as protective agents in the drought and freezing tolerance of many plant species. A direct proof of their ability to stabilize biological structures under stress conditions, however, is still lacking. Here we show that inulins (linear fructose polymers) isolated from chicory roots and dahlia tubers stabilize egg phosphatidylcholine large unilamellar vesicles during freeze-drying, while another polysaccharide, hydroxyethyl starch, was completely ineffective. Liposome stability was assessed after rehydration by measuring retention of the soluble fluorescent dye carboxyfluorescein and bilayer fusion. Inulin was an especially effective stabilizer in combination with glucose. Analysis by HPLC showed that the commercial inulin preparations used in our study contained no low molecular mass sugars that could be responsible for the observed stabilizing effect of the fructans. Fourier transform infrared spectroscopy showed a reduction of the gel to liquid-crystalline phase transition temperature of dry egg PtdCho by more than 20 degrees C in the presence of inulin. A direct interaction of inulin with the phospholipid in the dry state was also indicated by dramatic differences in the phosphate asymmetric stretch region of the infrared spectrum between samples with and without the polysaccharide.  (+info)

Fn-type chicory inulin hydrolysate has a prebiotic effect in humans. (2/73)

The partial enzymatic hydrolysis of chicory inulin (GFn; 2 < or =n < or =60) yields an oligofructose preparation that is composed of both GFn-type and Fn-type oligosaccharides (2 < or =n < or =7; 2 < or =m < or =7), where G is glucose, F is fructose, and n is the number of beta(2-->1) bound fructose moieties. Human studies have shown that feeding GFn-type oligomers significantly modifies the composition of the fecal microflora especially by increasing the number of bifidobacteria. The experiments reported here were used to test the hypothesis that the Fn-type molecules have the same property. During a controlled feeding study, 8 volunteers (5 females and 3 males) consumed 8 g/d of an Fn-rich product for up to 5 wk. Fecal samples were collected and analyzed for total anaerobes, bifidobacteria, lactobacilli, bacteroides, coliforms and Clostridium perfringens. Both 2 and 5 wk of oligofructose feeding resulted in a selective increase in bifidobacteria (P<0.01). In addition, a daily intake of 8 g of the Fn-type oligofructose preparation reduced fecal pH and caused little intestinal discomfort.  (+info)

Nitrate assimilation in chicory roots (Cichorium intybus L.) which acquire radial growth. (3/73)

Nitrate assimilation was analysed in chicory plants (Cichorium intybus L. cv. Turbo) during the early vegetative growth. Nitrate reductase (NR, EC 1.6.6.1) activity (NRA) was measured in roots and leaves at different developmental stages. During phase I, which corresponds to the structural growth (21-42 DAS), nitrate reduction mainly occurred in the roots. At the onset of the tuber formation (phase II), which is characterized by the formation of a cambium inducing a radial growth (42-63 DAS), NRA rapidly decreased in roots and developed in leaves. A tight correlation was found between the nitrate content, the amino acid level and NRA in roots and leaves. Northern blot and ELISA analysis showed that both levels of NR mRNA and NR protein were not modified during the time-course of the experiment suggesting that modification of nitrate assimilation was not controlled at a transcriptional level. In vitro NRA assayed in presence of either Mg2+ ions or EDTA showed that NR was influenced at least in part by a reversible phosphorylation/dephosphorylation reaction. Okadaic acid, a serine-threonine protein phosphatases inhibitor, strongly decreased NRA. Conversely, staurosporine, a serine-threonine protein kinases inhibitor, did not significantly change NRA in roots or leaves. Therefore, NRA was regulated at a post-translational level during the early vegetative growth by modifying the phosphorylation balance of the NR protein in chicory.  (+info)

Relative effects on virulence of mutations in the sap, pel, and hrp loci of Erwinia chrysanthemi. (4/73)

We constructed strains of Erwinia chrysanthemi EC16 with multiple mutations involving three virulence systems in this bacterium, namely pel (coding for the major pectate lyases pelABCE), hrp (hypersensitive response and pathogenicity), and sap (sensitivity to antimicrobial peptides). The relative effects on virulence of those mutations have been analyzed on potato tubers and chicory leaves. In potato tubers, the sap mutation (BT105) had a greater effect in the reduction of the virulence than the pel (CUCPB5006) and hrp (CUCPB5039) mutations. This reduction was similar to that observed in the pel-hrp double mutant (CUCPB5037). The analysis of the strains affected in Pel-Sap (BT106), Hrp-Sap (BT107), and Pel-Hrp-Sap (BT108) suggested that the effects of these mutations are additive. In chicory leaves, the mutation in the sap locus appeared to have a greater effect than in potato tubers. The competitive indices of strains BT105, UM1005 (Pel-), CUCPB5039, and CUCPB5037 have been estimated in vivo and in vitro. These results indicate that the mutation in the hrp locus can be complemented in vivo by coinfection, whereas the mutations in pel and sap cannot.  (+info)

Biosynthesis of germacrene A carboxylic acid in chicory roots. Demonstration of a cytochrome P450 (+)-germacrene a hydroxylase and NADP+-dependent sesquiterpenoid dehydrogenase(s) involved in sesquiterpene lactone biosynthesis. (5/73)

Sprouts of chicory (Cichorium intybus), a vegetable grown in the dark, have a slightly bitter taste associated with the presence of guaianolides, eudesmanolides, and germacranolides. The committed step in the biosynthesis of these compounds is catalyzed by a (+)-germacrene A synthase. Formation of the lactone ring is the postulated next step in biosynthesis of the germacrene-derived sesquiterpene lactones. The present study confirms this hypothesis by isolation of enzyme activities from chicory roots that introduce a carboxylic acid function in the germacrene A isopropenyl side chain, which is necessary for lactone ring formation. (+)-germacrene A is hydroxylated to germacra-1(10),4,11(13)-trien-12-ol by a cytochrome P450 enzyme, and is subsequently oxidized to germacra-1(10),4,11(13)-trien-12-oic acid by NADP+-dependent dehydrogenase(s). Both oxidized germacrenes were detected as their Cope-rearrangement products elema-1,3,11(13)-trien-12-ol and elema-1,3,11(13)-trien-12-oic acid, respectively. The cyclization products of germacra-1(10),4,11(13)-trien-12-ol, i.e. costol, were also observed. The (+)-germacrene A hydroxylase is inhibited by carbon monoxide (blue-light reversible), has an optimum pH at 8.0, and hydroxylates beta-elemene with a modest degree of enantioselectivity.  (+info)

Osmoregulated periplasmic glucan synthesis is required for Erwinia chrysanthemi pathogenicity. (6/73)

Erwinia chrysanthemi is a phytopathogenic enterobacterium causing soft rot disease in a wide range of plants. Osmoregulated periplasmic glucans (OPGs) are intrinsic components of the gram-negative bacterial envelope. We cloned the opgGH operon of E. chrysanthemi, encoding proteins involved in the glucose backbone synthesis of OPGs, by complementation of the homologous locus mdoGH of Escherichia coli. OpgG and OpgH show a high level of similarity with MdoG and MdoH, respectively, and mutations in the opgG or opgH gene abolish OPG synthesis. The opg mutants exhibit a pleiotropic phenotype, including overproduction of exopolysaccharides, reduced motility, bile salt hypersensitivity, reduced protease, cellulase, and pectate lyase production, and complete loss of virulence. Coinoculation experiments support the conclusion that OPGs present in the periplasmic space of the bacteria are necessary for growth in the plant host.  (+info)

Defoliation induces fructan 1-exohydrolase II in Witloof chicory roots. Cloning and purification of two isoforms, fructan 1-exohydrolase IIa and fructan 1-exohydrolase IIb. Mass fingerprint of the fructan 1-exohydrolase II enzymes. (7/73)

The cloning of two highly homologous chicory (Cichorium intybus var. foliosum cv Flash) fructan 1-exohydrolase cDNAs (1-FEH IIa and 1-FEH IIb) is described. Both isoenzymes could be purified from forced chicory roots as well as from the etiolated "Belgian endive" leaves where the 1-FEH IIa isoform is present in higher concentrations. Full-length cDNAs were obtained by a combination of reverse transcriptase-polymerase chain reaction (PCR), PCR and 5'- and 3'-rapid amplification of cDNA ends using primers based on N-terminal and conserved amino acid sequences. 1-FEH IIa and 1-FEH IIb cDNA-derived amino acid sequences are most homologous to a new group of plant glycosyl hydrolases harboring cell wall-type enzymes with acid isoelectric points. Unlike the observed expression profiles of chicory 1-FEH I, northern analysis revealed that 1-FEH II is expressed when young chicory plants are defoliated, suggesting that this enzyme can be induced at any developmental stage when large energy supplies are necessary (regrowth after defoliation).  (+info)

A glutathione S-transferase cDNA identified by mRNA differential display is upregulated during somatic embryogenesis in Cichorium. (8/73)

CHI-GST1, a cDNA encoding a glutathione S-transferase, was isolated by differential display in leaf tissues of chicory, during the early stages of somatic embryogenesis. Expression analysis of the gene by Northern blot indicated that the transcript accumulation is specific of the leaf developing somatic embryogenesis and is not observed in leaf tissue of the non-embryogenic cultivar.  (+info)

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