Localization of the 5S and 45S rDNA sites and cpDNA sequence analysis in species of the Quadrifaria group of Paspalum (Poaceae, Paniceae)

BACKGROUND AND AIMS: The Quadrifaria group of Paspalum (Poaceae, Paniceae) comprises species native to the subtropical and temperate regions of South America. The purpose of this research was to characterize the I genomes in five species of this group and to establish phylogenetic relationships among them. METHODS: Prometaphase chromatin condensation patterns, the physical location of 5S and 45S rDNA sites by fluorescence in situ hybridization (FISH), and sequences of five chloroplast non-coding regions were analysed. KEY RESULTS: The condensation patterns observed were highly conserved among diploid and tetraploid accessions studied and not influenced by the dyes used or by the FISH procedure, allowing the identification of almost all the chromosome pairs that carried the rDNA signals. The FISH analysis of 5S rDNA sites showed the same localization and a correspondence between the number of sites and ploidy level. In contrast, the distribution of 45S rDNA sites was variable. Two general patterns were observed with respect to the location of the 45S rDNA. The species and cytotypes Paspalum haumanii 2x, P. intermedium 2x, P. quadrifarium 4x and P. exaltatum 4x showed proximal sites on chromosome 8 and two to four distal sites in other chromosomes, while P. quarinii 4x and P. quadrifarium 2x showed only distal sites located on a variable number of small chromosomes and on the long arm of chromosome 1. The single most-parsimonious tree found from the phylogenetic analysis showed the Quadrifaria species partitioned in two clades, one of them includes P. haumanii 2x and P. intermedium 2x together with P. quadrifarium 4x and P. exaltatum 4x, while the other contains P. quadrifarium 2x and P. quarinii 4x. CONCLUSIONS: The subdivision found with FISH is consistent with the clades recovered with cpDNA data and both analyses suggest that the Quadrifaria group, as presently defined, is not monophyletic and its species belong in at least two clades.     

Curcuma longa Extract Exerts a Myorelaxant Effect on the Ileum and Colon in a Mouse Experimental Colitis Model, Independent of the Anti-Inflammatory Effect

Background

Curcuma has long been used as an anti-inflammatory agent in inflammatory bowel disease. Since gastrointestinal motility is impaired in inflammatory states, the aim of this work was to evaluate if Curcuma Longa had any effect on intestinal motility.

Methods

The biological activity of Curcuma extract was evaluated against Carbachol induced contraction in isolated mice intestine. Acute and chronic colitis were induced in Balb/c mice by Dextran Sulphate Sodium administration (5% and 2.5% respectively) and either Curcuma extract (200 mg/kg/day) or placebo was thereafter administered for 7 and 21 days respectively. Spontaneous contractions and the response to Carbachol and Atropine of ileum and colon were studied after colitis induction and Curcuma administration.

Results

Curcuma extract reduced the spontaneous contractions in the ileum and colon; the maximal response to Carbachol was inhibited in a non-competitive and reversible manner. Similar results were obtained in ileum and colon from Curcuma fed mice. DSS administration decreased the motility, mainly in the colon and Curcuma almost restored both the spontaneous contractions and the response to Carbachol after 14 days assumption, compared to standard diet, but a prolonged assumption of Curcuma decreased the spontaneous and Carbachol-induced contractions.

Conclusions

Curcuma extract has a direct and indirect myorelaxant effect on mouse ileum and colon, independent of the anti-inflammatory effect. The indirect effect is reversible and non-competitive with the cholinergic agent. These results suggest the use of curcuma extract as a spasmolytic agent.     

Mutations in two putative phosphorylation motifs in the tomato pollen receptor kinase LePRK2 show antagonistic effects on pollen tube length

The tip-growing pollen tube is a useful model for studying polarized cell growth in plants. We previously characterized LePRK2, a pollen-specific receptor-like kinase from tomato (1). Here, we showed that LePRK2 is present as multiple phosphorylated isoforms in mature pollen membranes. Using comparative sequence analysis and phosphorylation site prediction programs, we identified two putative phosphorylation motifs in the cytoplasmic juxtamembrane (JM) domain. Site-directed mutagenesis in these motifs, followed by transient overexpression in tobacco pollen, showed that both motifs have opposite effects in regulating pollen tube length. Relative to LePRK2-eGFP pollen tubes, alanine substitutions in residues of motif I, Ser(277)/Ser(279)/Ser(282), resulted in longer pollen tubes, but alanine substitutions in motif II, Ser(304)/Ser(307)/Thr(308), resulted in shorter tubes. In contrast, phosphomimicking aspartic substitutions at these residues gave reciprocal results, that is, shorter tubes with mutations in motif I and longer tubes with mutations in motif II. We conclude that the length of pollen tubes can be negatively and positively regulated by phosphorylation of residues in motif I and II respectively. We also showed that LePRK2-eGFP significantly decreased pollen tube length and increased pollen tube tip width, relative to eGFP tubes. The kinase activity of LePRK2 was relevant for this phenotype because tubes that expressed a mutation in a lysine essential for kinase activity showed the same length and width as the eGFP control. Taken together, these results suggest that LePRK2 may have a central role in pollen tube growth through regulation of its own phosphorylation status.     

Bacterial phospholipid molecular species analysis by ion-pair reversed-phase HPLC/ESI/MS

This work set out to optimize the detection and separation of several phospholipid molecular species on a reversed-phase column with the use of an electrospray ionization/mass spectrometry-compatible counter-ion. An application of this technique concerned a qualitative and quantitative analysis of bacterial membrane phospholipids extracted from Corynebacterium species strain 8. The phospholipid classes of strain 8 were identified as phosphatidylglycerol, phosphatidylinositol, diphosphatidylglycerol, and a peculiar lipid compound, acyl phosphatidylglycerol. Most of the molecular species structures were elucidated, and regarding phosphatidylglycerol, the fatty acid positions were clearly determined with the calculation of the sn-2/sn-1 intensity ratio of the fatty acyl chain fragments.     

Antiinflammatory Effect of Phytosterols in Experimental Murine Colitis Model: Prevention,Induction, Remission Study

Phytosterols, besides hypocholesterolemic effect, present anti-inflammatory properties. Little information is available about their efficacy in Inflammatory Bowel Disease (IBD). Therefore, we have evaluated the effect of a mixture of phytosterols on prevention/induction/remission in a murine experimental model of colitis. Phytosterols were administered x os before, during and after colitis induction with Dextran Sodium Sulfate (DSS) in mice. Disease Activity Index (DAI), colon length, histopathology score, ¹⁸F-FDG microPET, oxidative stress in the intestinal tissue (ileum and colon) and gallbladder ileum and colon spontaneous and carbachol (CCh) induced motility, plasma lipids and plasma, liver and biliary bile acids (BA) were evaluated. A similar longitudinal study was performed in a DSS colitis control group. Mice treated with DSS developed severe colitis as shown by DAI, colon length, histopathology score, ¹⁸F-FDG microPET, oxidative stress. Both spontaneous and induced ileal and colonic motility were severely disturbed. The same was observed with gallbladder. DSS colitis resulted in an increase in plasma cholesterol, and a modification of the BA pattern. Phytosterols feeding did not prevent colitis onset but significantly reduced the severity of the disease and improved clinical and histological remission. It had strong antioxidant effects, almost restored colon, ileal and gallbladder motility. Plasmatic levels of cholesterol were also reduced. DSS induced a modification in the BA pattern consistent with an increase in the intestinal BA deconjugating bacteria, prevented by phytosterols. Phytosterols seem a potential nutraceutical tool for gastrointestinal inflammatory diseases, combining metabolic systematic and local anti-inflammatory effects.     

Basement membrane maintenance in cultures of isolated thyroid follicles

Follicles from adult rat thyroid glands were isolated by digestion with collagenase followed by sieving. Electron microscopic studies have shown that basement membrane was present around each one of the isolated follicles. Follicles were cultured in vitro with or without thyrotropin and fibronectin. When cultured in a medium free of thyrotropin, basement membrane remained around them, while it was lacking in presence of this hormone.     

Thyrotropin effects on vesicle transfer and thyroid follicle morphogenesis: a stereological study in the rat

Incubation in a culture medium with and without TSH of 16 day-old foetal thyroid glands induces hypertrophy of the Golgi apparatus which may be correlated with a considerable increase in the number of secretory vesicles. A stereological study performed during the first 6 hr of incubation showed that: vesicle secretion was biphasic; vesicle secretion was heterogeneous with two different populations of vesicles; When TSH (20 mU and 80 mU) was added to the medium, the volume density of the follicular lumina increased; at least during the first 6 hr TSH seemed to be necessary to the formation of follicular lumina.     

Chloroplast genome differences between Paspalum dilatatum Poir and the related species P. notatum Flugge

 Chloroplast DNA (cpDNA) of Paspalum dilatatum and P. notatum was digested singly or in combination with the restriction endonucleases PstI, PvuII, SalI, KpnI and XhoI. Data obtained from filter hybridization experiments with barley and wheat cpDNA probes were used to construct restriction site maps of the chloroplast genomes of the Paspalum species. The cpDNA fragments were ordered into a circular configuration of approximately 139.3 kbp that contained two inverted repeat regions of approximately 23 kbp and a small and large single-copy region of approximately 11 kbp and 83 kbp, respectively. The cpDNA maps showed that P. dilatatum and P. notatum shared a large number of restriction sites with the proportion of shared restriction sites S=0.90. No restriction site differences were detected in the KpnI maps. Eight species-specific restriction site differences that could be used to identify the cytoplasm of each Paspalum species were identified in the PstI, PvuII, SalI, and XhoI cleavage maps. The overall structural organization of the Paspalum cpDNAs is rather similar to those of most cpDNAs from other plants. The results presented in this study will be of value for exploring further phylogenetic relationships within the genus Paspalum. Received: 27 February 1997 / Accepted: 7 March 1997     

PRODUCTION OF MUCILAGE BY THE ADRIATIC EPIPELIC DIATOM CYLINDROTHECA CLOSTERIUM (BACILLARIOPHYCEAE) UNDER NUTRIENT LIMITATION

The carbon partitioning of the epipelic diatom Cylindrotheca closterium (Ehrenberg) Reiman and Lewin isolated from the Adriatic Sea was studied in the laboratory under varying scenarios of nutrient limitation. Total number of cells, photosynthesis measured at 695 μmol photons·m ^{− 2}·s ^{− 1} irradiance (P_{695- μ mol}), chlorophyll ( a + c ) content, respiration, extracellular polymeric substances (EPS), total particulate carbohydrate (TPC), and dissolved carbohydrate were evaluated under nitrogen and phosphorus deficiencies in culture. The highest total number of cells was found in the control, whereas the nitrogen-limited treatment showed the lowest value. During the transition phase of growth, photosynthesis in the nitrogen-limited treatment was 3-fold lower than in the phosphorus-limited treatment and 4-fold lower than in the control. Differences in respiration rates and chlorophyll ( a + c ) content were even more marked. Dissolved carbohydrate remained the same in all the treatments, whereas during the transition and stationary phase, EPS presented the highest values under phosphorus limitation and the lowest in the control treatment. The production of EPS was closely linked to the periods of carbon assimilation (transition phase) in the nutrient depleted treatments, especially in the phosphorus-limited treatment. These results point out the relevance of the nutrient imbalance (nitrogen or phosphorus) in the production of EPS by the benthic or resuspended diatoms and suggest that these diatoms play an important role in nutrient-unbalanced systems like sediments or marine snow.     

Resetting of the circadian clock by phytochromes and cryptochromes in Arabidopsis.

The authors sought to investigate the role of phytochromes A and B (phyA and phyB) and cryptochromes 1 and 2 (cryl and cry2) in the synchronization of the leaf position rhythm in Arabidopsis thaliana. The seedlings were transferred from white light-dark cycles to free-running conditions with or without exposure to a light treatment during the final hours of the last dark period. The phase advance caused by a far-red light treatment was absent in the phyA mutant, deficient in the fhy1 and fhy3 mutants involved in phyA signaling, and normal in the cryl and cryl cry2 mutants. The phase shift caused by blue light was normal in the cry2 mutant; reduced in the phyA, cryl, phyA cry1, and cry1 cry2 mutants; and abolished in the phyA cryl cry2 triple mutant. The phase shift caused by red light was partially retained by the phyA phyB double mutant. The authors conclude that cryl and cry2 participate as photoreceptors in the blue light input to the clock but are not required for the phyA-mediated effects on the phase of the circadian rhythm of leaf position. The signaling proteins FHY1 and FHY3 are shared by phyA-mediated photomorphogenesis and phyA input to the clock.