Light control of amaranthin synthesis in isolated Amaranthus cotyledons

The effect of light on the amaranthin synthesis stimulated by exogenous precursors has been studied in isolated cotyledons of Amaranthus tricolor and A. caudatus. The results indicate that light acts at the level of the formation of the dihydropyridine moiety of the pigment.     

Paracoccus denitrificans SD1 mediated augmentation with indigenous mixed cultures for enhanced removal of N,N-dimethylformamide from industrial effluents

Bioaugmentation is an effective treatment method to reduce recalcitrant pollutants from polluted sites. Dimethylformamide (DMF) is a very common toxic organic solvent among the effluents of textile and pharma industries. DMF was degraded by pre-adapted Paracoccus denitrificans SD1 with indigenous mixed cultures in both bioaugmentation and non-bioaugmentation conditions. In free cell condition, augmentation was not much significant due to competition among the bacterial cells and direct exposure of cells to toxic level of DMF. To enhance the degradation of DMF, cells were entrapped in PVA–alginate matrix individually and collectively for bioaugmentation experiments. Bioaugmentation is successful when immobilized P. denitrificans SD1 is introduced higher inoculum volume with indigenous cultures in continuous packed bed reactor system. This treatment has succeeded in removing 91.3% of 3% (v/v) DMF from the industrial effluent. This investigation advocates that bioaugmentation enhances the DMF removal efficiency by about 20% when compared to individual degradation by P. denitrificans SD1.     

Extinction coefficients of chlorophyll a and B in n,n-dimethylformamide and 80% acetone

We found inconsistencies in the commonly used data for chlorophyll analysis in 80% acetone. Recently developed extinction coefficients for chlorophyll b in N,N-dimethylformamide (DMF) based on values from 80% acetone are low as a result of these inconsistencies. We determined extinction coefficients of chlorophyll a (Chl a) and chlorophyll b (Chl b) in DMF for wavelengths of 618 to 665 nanometers. The simultaneous equations necessary for quantifying Chl a, Chl b, or total Chl in DMF in the absence of other chlorophyllous pigments are: Chl a = 12.70A_664.5 - 2.79A₆₄₇; Chl b = 20.70 A₆₄₇ - 4.62A_664.5; total Chl = 17.90A₆₄₇ + 8.08A_664.5, where A = absorbance in 1.00 centimeter cuvettes and Chl = milligrams per liter.

N,N-Dimethylformamide is a very convenient solvent for Chl extraction since it is effective on intact plant parts and Chl is quite stable in DMF. There was no difference in the amount of Chl extracted when plant tissue was stored for 1 or 3 days at three temperatures, with or without solvent added.

     

Inhibition by amino acids of cytokinin-stimulated betacyanin synthesis inAmaranthus caudatus

A number of amino acids have been tested for their ability to inhibit the cytokinininduced synthesis of betacyanin inAmaranthus caudatus cotyledons. Under the conditions employed there was not any serious inhibition of pigment synthesis at amino acid concentrations belowca. 20 μg ml^-1. Amino acids such as methionine, γ-aminobutyric acid and leucine did not give rise to serious inhibition belowca. 200 μg ml^-1. At amino acid concentrations ofca. 2000 μg ml^-1, inhibitions of pigment synthesis was in all instances complete.     

Effect of jasmonic acid on morphogenesis and photosynthetic pigment level in Arabidopsis seedlings grown under green light

The role of jasmonic acid (JA) in plant photomorhogenesis under green light (GL) was studied. The effect of GL of different intensity (8.1 and 18.1 W/m²) with or without 1 μM JA treatment on growth of plants and photosynthetic pigment level was compared for two types of Arabidopsis thaliana (L.) Heynh. Landsberg erecta ecotype plants: Ler, the wild type, and hy4, a mutant. A much more pronounced growth of hypocotyls and cotyledons of Ler plants in GL was observed compared to that of hy4 with suppressed cryptochrome 1 (cry1), a GL photoreceptor. Treatment with JA in GL caused retardation of hypocotyl and cotyledon growth of Ler plants; however, it stimulated their growth in hy4 plants. JA reduced the chlorophyll a and total carotenoids levels in cotyledons of Arabidopsis plants in GL. Blocked GL signal transduction due to the absence of cry1 in hy4, as well as the higher intensity of GL reduced the negative effect of exogenous JA on growth of cotyledons and photosynthetic pigments. The data obtained provide a basis for discussion of interaction between the JA and GL signals in the growth regulation controlled by cry1. Original Russian Text ? I.F. Golovatskaya, R.A. Karnachuk, 2008, published in Fiziologiya Rastenii, 2008, Vol. 55, No. 2, pp. 240–244.     

Modulation of Chlorophyll, Carotene and Xanthophyll Formation by Penicillin, Benzyladenine and Embryonic Axis in Mung Bean (Phaseolus aureus L.) Cotyledons

Penicillin stimulated the synthesis of pigments in the cotyledonsof intact embryos and excised cotyledons of mung bean (Phaseolusaureus L.) and enhanced benzyladenine-induced accumulation ofchloroplast pigments. The presence of the embryonic axis duringlight exposure proved to be beneficial for chlorophyll synthesisby the cotyledons whereas its presence in dark germination producedan adverse effect. The possible involvement of nucleic acidand protein synthesis in light-regulated chlorophyll formationis suggested. The stimulating effect on pigment synthesis providedby penicillin in this system seems to involve a maintenanceof nucleic acid and protein synthesis. Phaseolus aureus L., mung bean, pigment synthesis, cotyledons     

Indoleacetaldehyde in cucumber seedlings

The presence of indoleacetaldehyde in cucumber (Cucumis sativus L.) cotyledons was demonstrated by thin layer chromatographic R_F values in three solvent systems, by the formation and hydrolysis of a bisulfite adduct, and by chemical reduction to indoleethanol and oxidation to indoleacetic acid. Bioassays indicated a minimum indoleacetaldehyde content in etiolated cotyledons of 0.7 μg per kg fresh weight. Tissue samples from all parts of both green and etiolated cucumber seedlings reduced exogenously supplied indoleacetaldehyde to indoleethanol.     

Counteraction of Trehalose on N,N-Dimethylformamide-Induced Candida rugosa Lipase Denaturation: Spectroscopic Insight and Molecular Dynamic Simulation

Candida rugosa lipase (CRL) has been widely used as a biocatalyst for non-aqueous synthesis in biotechnological applications, which, however, often suffers significant loss of activity in organic solvent. Experimental results show that trehalose could actively counteract the organic-solvent-induced protein denaturation, while the molecular mechanisms still don’t unclear. Herein, CRL was used as a model enzyme to explore the effects of trehalose on the retention of enzymatic activity upon incubation in N,N-dimethylformamide (DMF). Results showed that both catalytic activity and conformation changes of CRL influenced by DMF solvent were inhibited by trehalose in a dose-dependent fashion. The simulations further indicated that the CRL protein unfolded in binary DMF solution, but retained the native state in the ternary DMF/trehalose system. Trehalose as the second osmolyte added into binary DMF solution decreased DMF-CRL hydrogen bonds efficiently, whereas increased the intermolecular hydrogen bondings between DMF and trehalose. Thus, the origin of its denaturing effects of DMF on protein is thought to be due to the preferential exclusion of trehalose as well as the intermolecular hydrogen bondings between trehalose and DMF. These findings suggest that trehalose protect the CRL protein from DMF-induced unfolding via both indirect and direct interactions.     

Changes in leucyl-tRNAs and aminoacyl tRNA synthetases in developing and aging soybean cotyledons

Leucine specific tRNA of soybean cotyledons was frationated into six peaks (1–6). The relative amounts of Leu-tRNA 5 and 6 are lower in developing cotyledons than in germinating cotyledons. Leu-tRNA synthetase from developing cotyledons is less active in aminoacylating Leu-tRNA 5 and 6 compared to enzyme from 5-day-old germinating cotyledons. Leu-tRNA synthetase from cotyledons of germinating seedlings and developing cotyledons can be fractionated into three peaks (1–3). Peak 1 in the developing cotyledon is about 36% less than peak 1 from 5-day-old germinating cotyledons. Peaks 2 and 3 from developing cotyledons are about 10 and 18% higher than from germinating cotyledons, respectively. Peak 1 from developing cotyledons acylates all six species of Leu-tRNA in contrast with peak 1 from germinating cotyledons, which essentially acylates only Leu-tRNA 5 and 6. The specificity of peaks 2 and 3 towards Leu-tRNA 1–4 is identical in both the organs.     

Biochemical characteristics of thylakoid membranes in chloroplasts of dark-grown pine cotyledons

Japanese black pine (Pinus thunbergii) cotyledons were found to synthesize chlorophylls in complete darkness during germination, although the synthesis was not as great as that in the light. The compositions of thylakoid components in plastids of cotyledons grown in the dark and light were compared using sodium dodecyl sulfate-polyacrylamide gel electrophoresis patterns of polypeptides and spectroscopic determination of membrane redox components. All thylakoid membrane proteins found in preparations from light-grown cotyledons were also present in preparations from dark-grown cotyledons. However, levels of photosystem I, photosystem II, cytochrome b_[ill]/f, and light-harvesting chlorophyll-protein complexes in dark-grown cotyledons were only one-fourth of those in light-grown cotyledons, on a fresh weight basis. These results suggest that the low abundance of thylakoid components in dark-grown cotyledons is associated with the limited supply of chlorophyll needed to assemble the two photosystem complexes and the light-harvesting chlorophyll-protein complex.     

Synergistic hepatotoxicity of N,N-dimethylformamide with carbon tetrachloride in association with endoplasmic reticulum stress

N,N-Dimethylformamide (DMF) is an organic solvent extensively used in industries such as synthetic leather, fibers and films, and induces liver toxicity and carcinogenesis. Despite a series of experimental and clinical reports on DMF-induced liver failure, the mechanism of toxicity is yet unclear. This study investigated whether DMF in combination with a low dose of hepatotoxicant enhances hepatotoxicity, and if so, on what mechanistic basis. Treatment of rats with either DMF (50–500 mg/kg/day, for 3 days) or a single low dose of CCl₄ (0.2 ml/kg) alone caused small increases in plasma transaminases and lactate dehydrogenase activities. However, combinatorial treatment of DMF with CCl₄ markedly increased blood biochemical changes. Histopathology confirmed the synergism in hepatotoxicity. Moreover, DMF + CCl₄ caused PARP cleavage and caspase-3 activation, but decreased the level of Bcl-xL, all of which confirmed apoptosis of hepatocytes. Consistently, DMF + CCl₄ treatment markedly increased lipid peroxidation. By contrast, treatment of DMF in combination with lipopolysaccharide, acetaminophen or d-galactosamine caused no enhanced hepatotoxicity. Given the link between endoplasmic reticulum (ER) dysfunction and cell death, ER stress response was monitored after DMF and/or CCl₄ treatment. Whereas either DMF or CCl₄ treatment alone marginally changed the expression levels of glucose-regulated protein 78 and 94 and phosphorylated PKR-like ER-localized eIF2α kinase, concomitant treatment with DMF and CCl₄ synergistically induced them with increases in glucose-regulated protein 78 and C/EBP homologous protein mRNAs. Our results demonstrate that DMF treatment in combination with CCl₄ synergistically increases hepatocyte death, which may be associated with the induction of severe ER stress.     

Uptake and effects of N-benzyladenine in excised watermelon cotyledons: influence of cotyledon age

Some characteristics of uptake of [8-¹⁴C]N⁶-benzyladenine (BA) by watermelon (Citrullus vulgaris Schrad., cv. Fairfax) cotyledons that were either excised immediately after 24 hours inhibition (day 0) or cultured in the dark for 48 hours on moist filter paper (day 2) have been compared.

The uptake of BA seems to be passive in cotyledons of both kinds. The initial rate of uptake is, however, much slower in day 2 cotyledons. This is probably due to a higher resistance of cell membranes to BA influx. When the day 2 cotyledons are frozen and thawed, so that the membrane barrier is abolished, the amount of BA taken up is the same as in day 0 cotyledons.

In spite of the lower rate of uptake, the physiological effects of BA in day 2 cotyledons are as strong as in day 0 cotyledons and occur with a shorter lag time. Sensitivity to BA seems indeed to start 24 to 48 hours after excision.

     

Influence de la 6-benzylaminopurine sur la différenciation plastidiale dans les cotylédons de concombre

Treatment with 6-benzylaminopurine (6-BAP; 10⁻⁵ g/ml) accelerates the growth of detached cucumber cotyledons (Cucumis sativas L.), primarily through an increased water uptake by the tissues. A comparative study of pigment composition and ultrastructure in 6-BAP treated and untreated cotyledons shows that cytokinin, in the presence of light, accelerates the transformation of etioplasts into chloroplasts. 6-BAP also enhances the synthesis of membrane precursors as indicated by the formation of a dense prolamellar body and by the persistence of a pseudo-cristalline structure in 6-BAP treated material. Stimulation of biosynthetic activity by cytokinin leads simultaneously to an increase in the rate of the pigment synthesis and to an acceleration in the building of the lamellar system. Furthermore, chloroplasts of 6-BAP treated cotyledons show abnormal features such as a striking increase in the number of thylacoids per granum and a poor development of the intergranal system.     

Accumulation of photosynthetic pigments in Larix decidua Mill. and Picea abies (L.) Karst. cotyledons treated with 5-aminolevulinic acid under different irradiation

European larch (Larix decidua Mill.) and Norway spruce [Picea abies (L.) Karst.] synthesize chlorophyll (Chl) in darkness. This paper compares Chl accumulation in 14-d-old dark-grown seedlings of L. decidua and P. abies after shortterm (24 h) feeding with 5-aminolevulinic acid (ALA). We used two ALA concentrations (1 and 10 mM) fed to cotyledons of both species in darkness and in continuous light. The dark-grown seedlings of L. decidua accumulated Chl only in trace amounts and the seedlings remained etiolated. In contrast, P. abies seedlings grown in darkness were green and had significantly higher Chl content. After ALA feeding, higher protochlorophyllide (Pchlide) content was observed in L. decidua than in P. abies cotyledons incubated in darkness. Although short-term ALA feeding stimulated the synthesis of Pchlide, Chl content did not change significantly in cotyledons incubated in darkness. The Chl accumulation in cotyledons fed with ALA was similar to the rate of Chl accumulation in the controls. Higher Chl accumulation was reported in control samples after illumination: 86.9% in L. decidua cotyledons and 46.4% in P. abies cotyledons. The Chl content decreased and bleaching occurred in cotyledons incubated with ALA in light due to photooxidation. Analyses of Chlbinding proteins (D1 and LHCIIb) by Western blotting proved differences between Chl biosynthesis in L. decidua and P. abies seedlings in the dark and in the light. No remarkable increase was found in protein accumulation (D1 and LHCIIb) after ALA application. Our results showed interspecific difference in Chl synthesis between two gymnosperms. Shortterm ALA feeding did not stimulate Chl synthesis, thus ALA synthesis was not the rate-limiting step in Chl synthesis in the dark.     

In situ synthesis of (5-phenyl-1H-pyrazole-3-carboxylic acid) metal complexes and their stable supramolecular microporous frameworks

By in situ generation of ppc ligand in the presence MCl₂ and 3-phenyl-1H-pyrazole-5-carbohydrazide at room temperature, the complexes, [M(ppc)₂(DMF)₂]·2H₂O (M = Co (1) and Ni (2); ppc = 5-phenyl-1H-pyrazole-3-carboxylic acid), were synthesized and characterized by single-crystal X-ray diffraction, IR spectrum, UV spectra and elemental analysis. X-ray structural analysis revealed that the complexes were formed into 3D supramolecular polymers via C-H?O and π?π interactions. The 3D supramolecular networks of two complexes were constructed from 1D nanochannels along the c-direction with the disorder DMF and water solvent molecules shuttling easily. TG and powder X-ray diffraction analysis showed two complexes had high stability when DMF and H₂O molecules were removed. Upon DMF molecules liberated, two complexes become stable microporous solid with coordination-unsaturated [M(ppc)₂] as center. The electrochemical properties were also investigated.     

Lack of embryonic axis control in Pisum cotyledon mitochondria

Respiratory control ratio (RCR), ADP: O and oxygen uptake by isolated mitochondria from cotyledons of the genus Pisum were studied. It is shown that in P. sativum the embryonic axis has a slight effect on the behaviour of the mitochondria in the cotyledons, accelerating their degeneration. The inducing factor is transferred within 1 hr from the onset of imbibition from the axis to the cotyledon. In P. elatius the embryonic axis completely lacked an effect on the mitochondria in the cotyledons. Mitochondria in P. elatius seemed to be highly organized and not leaky.     

Purine synthesis and catabolism in soybean seedlings : the biogenesis of ureides

The ureides, allantoin and allantoic acid, are the major nitrogenous substances transported within the xylem of N₂-fixing soybeans (Glycine max L. Merr. cv Amsoy 71). The ureides accumulated in the cotyledons, roots and shoots of soybean seedlings inoculated with Rhizobium or grown in the presence of 10 millimolar nitrate. The patterns of activity for uricase and allantoinase, enzymes involved in ureide synthesis, were positively correlated with the accumulation of ureides in the roots and cotyledons. Allopurinol and azaserine inhibited ureide production in 3-day-old cotyledons while no inhibition was observed in the roots. Incubation of 4-day-old seedlings with [¹⁴C]serine indicated that in the cotyledons ureides arose via de novo synthesis of purines. The source of ureides in both 3- and 4-day-old roots was probably the cotyledons. The inhibition of ureide accumulation by allopurinol but not azaserine in 8-day-old cotyledons suggested that ureides in these older cotyledons arose via nucleotide breakdown. Incubation of 8-day-old plants with [¹⁴C]serine suggested that the roots had acquired the capability to synthesize ureides via de novo synthesis of purines. These data indicate that both de novo purine synthesis and nucleotide breakdown are involved in the production of ureides in young soybean seedlings.     

Chloroplast Degradation in Agcing Cotyledons of Pumpkin

The cotyledons of Cucurbita maxima provide a system which permitsthe isolation of chloro-plasts in various states of structuraldisintegration. These states are defined and corrlated withthe morphological appearance of the cotyledon and its electronmicroscopic and biochemical parameters. Removal of growth abovethe cotyledons results in cotyledons whose chloroplasts do notchange in pigment composition. The connection between light-harvestingapparatus and electron transport components remains intact inthese plastids while the electron transport chain undergoesage-induced alterations. The implications of these observationson studies of structure-function relationships in photosynthesisare discussed.     

Synthesis, molecular structure, and redox behavior of an oxo-bridged dimer of a ruthenium-bpb nitrosyl

We have prepared the oxo-bridged dimer [Ru(bpb)(NO]₂(μ-O) in 60% isolated yield from the reaction of the known Ru(bpb)(NO)Cl with silver nitrite. The compound exhibits a υ_NO of 1758 cm⁻¹ (KBr pellet). The crystal structure reveals a linear ON-Ru-O-Ru-NO fragment with the oxo atom serving as an inversion center in the molecule. The redox behavior in DMF is characterized by a reversible reduction followed by a second but irreversible reduction in this solvent.