Osmoregulation in hypocotyls of etiolated mung bean seedlings with or without cotyledons in response to water-deficient stress

Effects of water-deficient stress and cotyledon excision on osmoregulation in hypocotyls of dark-grown mung bean seedlings were studied, and following results were obtained. Water-deficient stress inhibited hypocotyl elongation either in intact or decotylized seedlings. The inhibition was more conspicuous in decotylized seedlings than in intact ones. Water-deficient stress decreased osmotic potential in hypocotyls, while cotyledon excision increased it. The concentrations of soluble sugars, free amino acids and potassium ions in hypocotyls of intact or decotylized seedlings increased in response to water-deficient stress. Cotyledon excision reduced the concentration of soluble sugars and free amino acids, but it did not change the concentration of potassium ions, suggesting that a part of soluble sugars and free amino acids is transported from cotyledons. Unlike cotyledon excision, excision of the apex or roots had no influence on osmoregulation in response to water-deficient stress. Segments excised from hypocotyls had the ability to osmoregulate in response to water-deficient stress. Based on these results, the role of cotyledons in osmoregulation in response to water-deficient stress and quantitative relationships between osmotic potential and hypocotyl elongation in etiolated mung bean seedlings are discussed.     

Active transport and mediated diffusion of glucose and other monosaccharides inEndomyces magnusii

After growth on sucrose or glucose,Endomyces magnusii possesses a monosaccliaride uptake which resembles that ofSaccharomyces cerevisiae (a high K_Tof uptake, preference for α-anomers of D-xylose and D-glucose, enhanced uptake during anaerobiosis, attainment of a diffusion equilibrium). The uptake is inhibited by other monosaccharides and especially strongly by D-galactose. In the absence of high concentrations of metabolizable sugars,E. magnusii develops a capacity to accumulate 3-O-methyl-D-glucose and D-xylose against a concentration gradient the new system displaying a high affinity for glucose (K_T < 0.1 mM), repression by glucose, mannose or galactose. Cycloheximide (0.2 %) blocks the formation of the active system.     

Retarding effect of inhibitors of protein and RNA synthesis on chlorophyll and protein breakdown

Cycloheximide, ethionine,p-fluorophenylalanine, 6-azauracil, 5-diazouracil and vanillin, applied at relatively high concentrations, retarded the yellowing of kale (Brassica oleracea L. var.acephala) leaf discs in darkness, and stimulated it in light. All the compounds inhibited protein synthesis and retarded protein breakdown. Cycloheximide,p-fluorophenylalanine, diazouracil and vanillin also inhibited the incorporation of uracil-¹⁴C into RNA of senescing discs. Abscisic acid and 2-chloroethylphosphonic acid accelerated yellowing both in darkness and in light and stimulated the protein breakdown in senescing discs. Abscisic acid inhibited the chlorophyll, protein and RNA synthesis in detached, greening cucumber cotyledons. There was no direct correlation between the activity of a given compound as an inhibitor of yellowing in darkness, and the degree of inhibition of RNA synthesis. The arrest of yellowing in darkness is possibly a consequence of the retarded rate of protein breakdown. Yellowing in light, on the contrary, is dependent on the actual rate of protein synthesis.     

Rhythmic changes in ribonuclease activity in relation to nucleic acid synthesis in cotyledons ofChenopodium rubrum L. and to floral induction of the plants

Ribonuclease (RNAse) activity was investigated in cotyledons ofChenopodium rubrum plants subjected to various conditions of illumination (photoperiodic induction, continuous light, induction cancelled by interrupting the dark period by a light-break). At the end of the dark period of the single inductive cycles RNAse activity of induced plants was inferior to that of plants grown in continuous light. At the end of the first two cycles the activity was lowest after the interruption of the dark period by light. The investigation of the enzyme in 6h intervals showed rhythmic changes in activity to occur in induced plants. Enzyme activity followed a pattern opposed to this of nucleic acid (NA) synthesis in the cotyledons. In plants from continuous light the enzyme activity did not show any rhythm and in plants having obtained a light-break during the inductive period the rhythm was less distinct than in the induced ones. The period length of the endogenous rhythm of NA synthesis in the cotyledons is about half as long as this of flowering and the peaks of flowering coincide with the throughs of NA synthesis.     

Changes in nucleic acid synthesis in cotyledons and apical buds of chenopodium rubrum l. associated with photoperiodic induction

The nucleic acid (NA) fractions were analyzed in cotyledons and apical buds ofChenopodium rubrum plants by means of acrylamide electrophoresis at the end of the dark period of a different number of photoperiodic cycles or after transfer of the plants to light for 4 h subsequent to the termination of the dark period. The plants were labelled with³²P three hours prior to sampling. The uptake of³²P into the cotyledons was higher in light than in darkness in all cases, however, it was not in correlation with³²P incorporation into the NA fractions. After one dark period lasting 8 or 16 h NA synthesis in light did not increase in comparison with darkness. After two or more photoperiodic cycles NA synthesis was higher in light than in darkness irrespective of whether the dark period lasted 8 or 16 h. NA synthesis was distinctly highest after two inductive cycles lasting 16 h. In buds NA synthesis was slightly shifted in favour of ribosomal RNA as compared with cotyledons. In the cotyledons the increase in light was mainly duo to a raise of rRNA synthesis whereas in the buds synthesis of sRNA and DNA increased, as well.     

Polysome assembly and RNA synthesis during phytochrome-mediated photomorphogenesis in mustard cotyledons

The effect of phytochrome (high irradiance reaction, elicited by continuous far-red light) on cellular polysome levels was investigated using ribosome-isolation procedures which prevent the methodological artifacts inherent in previous studies on polysomes. By including the large pool of ribosomal subunits in the analysis and using the ratio (polysomes: monomers + subunits) as a quantitative estimate of the translational capacity of the ribosomes in mustard (Sinapis alba L.) cotyledons, we found the following results: 1) After a lag-phase of less than 30 min, phytochrome induces a massive increase in the relative amount of cytosolic (free) polysomes at the expense of ribosomal subunits. 2) Cytosolic and membrane-bound polysomes are increased by phytochrome in constant proportions (constant ratio of 65:35 in light and darkness). 3) Simultaneously with the light-mediated increase of the polysome level there is an increased incorporation of newly synthesized (labeled) non-ribosomal RNA, presumably mRNA, into the polysomes which can be kinetically discriminated from the slower incorporation of newly synthesized (labeled) rRNA. 4) Cordycepin strongly inhibits the synthesis of RNA and completely prevents the light-mediated increase of polysomes. 5) The electrophoretic patterns of the in-vitro translation products obtained with polysomal polyadenylated RNA from dark-grown and light-grown cotyledons showed no significant qualitative differences. We conclude from these results that photomorphogenesis of mustard cotyledons is related to a massive increase of newly synthesized mRNA leading to a correspondingly increased recruitment of ribosomal subunits into polysomes. The phytochrome-induced increase of translatable mRNA involves mainly quantitative changes in the production of mRNA species which are also present in the dark-grown cotyledons.     

Effects of chilling stress on the accumulation of soluble sugars and their key enzymes in <Emphasis Type="Italic">Jatropha curcas</Emphasis> seedlings

As osmolytes and signaling molecules, soluble sugars participate in the response and adaptation of plants to environmental stresses. In the present study, we measured the effect of chilling (12 °C) stress on the contents of eight soluble sugars in the leaves, cotyledons, stems, and roots of Jatropha curcas seedlings, as well as on the activities of eight rate-limiting enzymes that are critical to the metabolism of those soluble sugars. Chilling stress promoted both starch hydrolysis and soluble sugar accumulation. The soluble sugar contents of the leaves and cotyledons were affected more than that of the stems and roots. Meanwhile, the activities of the corresponding metabolic enzymes (e.g., β-amylase, uridine diphosphate glucose phosphorylase, and sucrose phosphate synthase) also increased in some organs. The gradual increase of soluble neutral alkaline invertase activity in the four studied organs suggested that sucrose catabolic production, such as glucose and fructose, was especially important in determining resistance to chilling stress and hexose signal transduction pathway. In addition, the substantial accumulation of raffinose family oligosaccharides and increase in corresponding metabolic enzyme activity suggested that galactinol and raffinose play an important role in determining the chilling resistance of J. curcas. Together, these findings establish a foundation for determining the relationship between the chilling resistance and soluble sugar accumulation of J. curcas and for investigating the mechanisms underlying sugar signaling transduction and stress responses.     

Characterization of rumen bacterial strains isolated from enrichments of rumen content in the presence of propolis

Propolis presents many biological properties, including antibacterial activities, and has been proposed as an additive in ruminant nutrition. Twenty bacterial strains, previously isolated from enrichments of Brazilian cow rumen contents in the presence of different propolis extracts (LLOS), were characterized using phenotyping and 16S rRNA identification. Seven strains were assigned to Streptococcus sp., most likely S. bovis, and were all degrading starch. One amylolytic lactate-utilizing strain of Selenomonas ruminantium was also found. Two strains of Clostridium bifermentans were identified and showed proteolytic activity. Two strains were assigned to Mitsuokella jalaludinii and were saccharolytic. One strain belonged to a Bacillus species and seven strains were affiliated with Escherichia coli. All of the 20 strains were able to use many sugars, but none of them were able to degrade the polysaccharides carboxymethylcellulose and xylans. The effect of three propolis extracts (LLOS B1, C1 and C3) was tested on the in vitro growth of four representative isolates of S. bovis, E. coli, M. jalaludinii and C. bifermentans. The growth of S. bovis, E. coli and M. jalaludinii was not affected by the three propolis extracts at 1 mg ml^?1. C. bifermentans growth was completely inhibited at this LLOS concentration, but this bacterium was partially resistant at lower concentrations. LLOS C3, with the lower concentration of phenolic compounds, was a little less inhibitory than B1 and C1 on this strain.     

An inducible riboflavin synthetase from a pseudomonad

Riboflavin synthetase activity is induced in a strain ofPseudomonas fluorescenspulida intermediate only under conditions permitting an accumulation of compound P, a 2,4-dioxopteridine, in the medium. The effect of different amino acids and sugars on the production of compound P and riboflavin synthetase was determined. The enzyme was partially destroyed by ammonium sulphate fractionation. It is inhibited by heavy metal ions and PCMB. PCMB inhibition can be almost completely reversed by GSH.     

Effect of sugars,Na+-, and K+-ions on biopterin transport in Crithidia fasciculata

Biopterin uptake by Crithidia fasciculata is pH dependent with optimum at pH 6 and is strongly inhibited by 0.5 mM NAA and DNP,respectively. Both inhibitors also reduce respiration by 40% (NAA) and 97% (DNP). K⁺-ions (1.1%) and K⁺/Na⁺ (0.5% each) stimulate biopterin uptake to the same high extent, but ouabain has no effect, thereby ruling out involvement of Na⁺/K⁺ pump. In absence of these ions, even in 5% glucose solution biopterin uptake is reduced to minimum. Proton excretion seems to be linked to sugar uptake. Both these sugars seem to have the same site of entry, demonstrated by competitive uptake, though D-glucose is taken up much faster by Crithidia than D-galactose. DNP (0.5 mM) causes greater proton excretion in glucose than in galactose medium. With NAA (0.5 mM) proton excretion is inhibited in both glucose and galactose media. D-glucose promotes greater biopterin uptake than D-galactose.     

Role of spermidine and spermine in alleviation of drought-induced oxidative stress and photosynthetic inhibition in Chinese dwarf cherry (Cerasus humilis) seedlings

To investigate the effect of exogenous Spermidine (Spd) and Spermine (Spm) on drought-induced damage to seedlings of Cerasus humili, relative water content (RWC), malondialdehyde content, relative electrolyte leakage, superoxide (O₂ ^?, SOD) generation rate, hydrogen peroxide (H₂O₂), endogenous polyamines (PAs), antioxidant enzymes [SOD and peroxidase (POD)] activities, PA-biosynthetic enzymes [arginine decarboxylase (ADC), ornithine decarboxylase (ODC), S-adenosylmethionine decarboxylase (SAMDC)] activities, as well as photosynthetic parameters, were measured in greenhouse cultured seedlings of C. humili. The results showed that either exogenous Spd or Spm (0.2 mM) significantly enhanced the level of RWC and prevented drought-induced lipid peroxidation. They also significantly enhanced photosynthetic capability and decreased O₂ ^? generation rate and H₂O₂ content. In addition, Spd and Spm helped to maintain SOD and POD activities in C. humili seedlings subjected to water stress, suggesting that they exerted a positive effect on antioxidant systems. The contents of endogenous free putrescine, Spd and Spm were increased to different extents in water-stressed C. humili seedlings. By the end of drought treatment (21 days) with exogenous Spd or Spm, the contents of free Spd increased by 30 and 38 %, respectively, and endogenous Spm increased by 41 and 26 %, respectively, compared with water-stressed plants. Furthermore, exogenous Spd or Spm enhanced the activities of ADC, ODC, and SAMDC. The pretreatment with Spd or Spm prevents oxidative damage induced by drought, and the protective effect of Spd was found to be greater than that of Spm.     

Mechanism of proanthocyanidins-induced alcoholic fermentation enhancement in Saccharomyces cerevisiae

Our previous work revealed proanthocyanidins (PAs) could pose significant enhancement on the activity of H⁺-ATPase and fermentation efficiency after a transient initial inhibition (Li et al in Am J Enol Vitic 62(4):512–518, 2011). The aim of the present work was to understand the possible mechanism for this regulation. At Day 0.5 the gene expression level of PMA1 in AWRI R₂ strain supplemented with 1.0 mg/mL PAs was decreased by around 54 % with a 50 % and a 56.5 % increase in the concentration of intracellular ATP and NADH/NAD⁺ ratio, respectively, compared to that of control. After the transient adaptation, the gene expression levels of PMA1 and HXT7 in PAs-treated cells were enhanced significantly accompanied by the decrease of ATP contents and NADH/NAD⁺ ratio, which resulted in the high level of the activities of rate-limiting enzymes. PAs could pose significant effects on the fermentation via glucose transport, the energy and redox homeostasis as well as the activities of rate-limiting enzymes in glycolysis.     

Adenosylmethionine Decarboxylase 1 (AMD1)-Mediated mRNA Processing and Cell Adhesion Activated & Inhibited Transition Mechanisms by Different Comparisons Between Chimpanzee and Human Left Hemisphere

To understand adenosylmethionine decarboxylase 1 (AMD1)-mediated mRNA processing and cell adhesion activated & inhibited transition mechanisms between chimpanzee and human left hemisphere, AMD1-activated different complete (all no positive correlation, Pearson correlation coefficient < 0.25) and uncomplete (partly no positive correlation except AMD1, Pearson < 0.25) networks were identified in higher human compared with lower chimpanzee left hemisphere from the corresponding AMD1-stimulated (Pearson ≥ 0.25) or inhibited (Pearson ≤ ?0.25) overlapping molecules of Pearson and GRNInfer, respectively. This result was verified by the corresponding scatter matrix. As visualized by GO, KEGG, GenMAPP, BioCarta, and disease database integration, we proposed mainly that AMD1-stimulated different complete network was involved in AMD1 activation with cytoplasm ubiquitin specific peptidase (tRNA-guanine transglycosylase) to nucleus paired box-induced mRNA processing, whereas the corresponding inhibited network participated in AMD1 repression with cytoplasm protocadherin gamma and adaptor-related protein complex 3-induced cell adhesion in lower chimpanzee left hemisphere. However, AMD1-stimulated network contained AMD1 activation with plakophilin and phosphodiesterase to SH3 binding glutamic acid-rich protein to dynein and zinc finger-induced cell adhesion, whereas the corresponding inhibited different complete network included AMD1 repression with mitochondrial denine nucleotide translocator, brain protein, and ADH dehydrogenase to ribonucleoprotein-induced mRNA processing in higher human left hemisphere. Our AMD1 different networks were verified by AMD1-activated or -inhibited complete and uncomplete networks within and between chimpanzee left hemisphere or (and) human left hemisphere.