Identification of differentially expressed salt-responsive proteins in roots of two perennial grass species contrasting in salinity tolerance

This study was designed to identify physiological responses and differential proteomic responses to salinity stress in roots of a salt-tolerant grass species, seashore paspalum (Paspalum vaginatum), and a salt-sensitive grass species, centipedegrass (Eremochloa ophiuroides). Plants of both species were exposed to salinity stress by watering the soil with 300 mM NaCl solution for 20 d in a growth chamber. The 2-DE analysis revealed that the abundance of 8 protein spots significantly increased and 14 significantly decreased in seashore paspalum, while 19 and 16 protein spots exhibited increase and decrease in abundance in centipedegrass, respectively. Eight protein spots that exhibited enhanced abundance in seashore paspalum under salinity stress were subjected to mass spectrometry analysis. Seven protein spots were successfully identified, they are peroxidase (POD, 2.36-fold), cytoplasmic malate dehydrogenase (cMDH, 5.84-fold), asorbate peroxidase (APX, 4.03-fold), two mitochondrial ATPSδ chain (2.26-fold and 4.78-fold), hypothetical protein LOC100274119 (5.01-fold) and flavoprotein wrbA (2.20-fold), respectively. Immunblotting analysis indicated that POD and ATPSδ chain were significantly up-regulated in seashore paspalum at 20 d of salinity treatment while almost no expression in both control and salt treatment of centipedegrass. These results indicated that the superior salinity tolerance in seashore paspalum, compared to centipedegrass, could be associated with a high abundance of proteins involved in ROS detoxification and energy metabolism.     

Atorvastatin prevents peroxisome proliferator-activated receptor γ coactivator-1 (PGC-1) downregulation in lipopolysaccharide-stimulated H9c2 cells

Although abnormalities in cardiac fatty acid metabolism are involved in the development of several cardiac pathologies, the mechanisms underlying these changes are not well understood. Given the prominent role played by peroxisome proliferator-activated receptor β/δ (PPARβ/δ in cardiac fatty acid metabolism, the aim of this study was to examine the effects of nuclear factor (NF)-κB activation on the activity of this nuclear receptor. Embryonic rat heart-derived H9c2 cells stimulated with lipopolysaccharide (LPS) showed a reduction (38%, P < 0.05) in the mRNA levels of the PPARβ/δ-target gene pyruvatedehydrogenase kinase 4 (PDK4) that was prevented in the presence of the NF-κB inhibitors parthenolide (10 μM) and atorvastatin (10 μM). Electrophoretic mobility shift assay revealed that both parthenolide and atorvastatin significantly decreased LPS-stimulated NF-κB binding activity in H9c2 cardiac cells. LPS-stimulation of H9c2 cardiac cells also led to a 30% reduction (P < 0.05) in the mRNA levels of PPARγ Coactivator 1 (PGC-1) that was consistent with the reduction in the protein levels of this coactivator. In the presence of either atorvastatin or parthenolide, the reduction in PGC-1 expression was prevented. Co-immunoprecipitation studies showed that LPS-stimulation led to a reduction in the physical interaction between PGC-1 and PPARβ/δ and that this reduction was prevented in the presence of atorvastatin. Finally, electrophoretic mobility shift assay revealed that parthenolide and atorvastatin prevented LPS-mediated reduction in PPARβ/δ binding activity in H9c2 cardiac cells. These results suggest that LPS-mediated NF-κB activation inhibits the expression of genes involved in fatty acid metabolism by a mechanism involving reduced expression of PGC-1, which in turn affects the PPARβ/δ transactivation of target genes involved in cardiac fatty acid oxidation.     

Porphyrogenic effects and induction of heme oxygenase in vivo by δ-aminolevulinic acid

The effects of single large doses of the porphyrin-heme precursor ?d-aminolevulinic acid on tissue porphyrins and on δ-aminolevulinate synthase and heme oxygenase, the rate-living enzymes of liver heme synthesis and degradation respectively, were studied in the chick embryo in ovo, in the mouse and in the rat. δ-Aminolevulinic acid treatment produced a distinctive pattern characterized by extensive tissue porphyrin accumulation and alterations in these rate-limiting enzymes in the liver. Repression of basal or allylisopropylacetamide-induced liver δ-aminolevulinate synthase was observed and, in the mouse and the rat, induction of liver heme oxygenase after δ-aminolevulinic acid treatment, in a manner similar to the known effects of hemin on these enzymes. In the chick embryo liver in ovo heme oxygenase was substantially higher than in rat and mouse liver, and was not significantly induced by δ-aminolevulinic acid or other compounds, including hemin, CS₂ and CoCl₂. Levulinic acid, an analogue of δ-aminolevulinic acid, did not induce heme oxygenase in mouse liver. δ-Aminolevunilic acid treatment did not impair ferrochelatase activity but was associated with slight and variable decreases in liver cytochrome P-450. Treatment of chick embryos with a small ‘priming’ dose of 1,4-dihydro-3,5-dicarbethoxycollidine, which impairs liver ferrochelatase activity, accentuated porphyrin accumulation after δ-aminolevulinic acid in the liver. These observations indicate that exogenous δ-aminolevulinic acid is metabolized to porphyrins in a number of tissues and, at least in the liver, to a physiologically significant amount of heme, thereby producing an increase in the size of one or more of the heme pools that regulate both heme systhesis and degradation. It is also possible than when δ-aminolevulinic acid is markedly overproduced in vivo it may be transported to many tissues and re-enter the heme pathway and alter porphyrin-heme metabolism in cells and tissues other than those in which its overproduction primarily occurs.     

树轮木质素甲氧基稳定氢同位素比率测定方法研究进展

在森林树木合成的有机化合物中,氢元素(H)主要源于大汽水,经植物光合与生理代谢参与生物地球化学循环。近年来,树轮木质素甲氧基稳定氢同位素比率(δ²H_LM)作为新的古气候和古环境研究的代用指标,重建了多个地区的降水稳定同位素比率及气候变化信息,展现了其特有的优势。本文综述了现有树轮δ²H_LM测定的详细分析方法和基本原理,从树轮木质素含量、单体组成等方面对树轮δ²H_LM测定方法的稳定性和有效性进行评价,阐述了树轮木质素甲氧基稳定同位素指标现有研究成果。中纬度地区森林树轮δ²H_LM在记录气温变化和降水稳定同位素变化等方面有着巨大的潜力。但是树轮δ²H_LM的研究尚处于起步阶段,主要表现为: 1) 研究区局限于北半球中纬度地区,研究对象局限于针叶树种;2) 高分辨率树轮δ²H_LM研究有待开展,以弥补硝化纤维稳定氢同位素记录的局限;3) 树轮δ²H_LM在植物生理和森林生态研究方面的潜力有待开发。     

Cyclic biphalin analogues with a novel linker lead to potent agonist activities at mu,delta, and kappa opioid receptors

In an effort to improve biphalin’s potency and efficacy at the µ-(MOR) and δ-opioid receptors (DOR), a series of cyclic biphalin analogues 1–5 with a cystamine or piperazine linker at the C-terminus were designed and synthesized by solution phase synthesis using Boc-chemistry. Interestingly, all of the analogues showed balanced opioid agonist activities at all opioid receptor subtypes due to enhanced κ-opioid receptor (KOR) activity. Our results indicate that C-terminal flexible linkers play an important role in KOR activity compared to that of the other cyclic biphalin analogues with a hydrazine linker. Among them, analogue 5 is a potent (Ki?=?0.27, 0.46, and 0.87?nM; EC₅₀?=?3.47, 1.45, and 13.5?nM at MOR, DOR, and KOR, respectively) opioid agonist with high efficacy. Based on the high potency and efficacy at the three opioid receptor subtypes, the ligand is expected to have a potential synergistic effect on relieving pain and further studies including in vivo tests are worthwhile.     

Inactivation of glycogen synthase kinase 3β (GSK-3β) enhances mitochondrial biogenesis during myogenesis

Background

Mitochondrial biogenesis is crucial for myogenic differentiation and regeneration of skeletal muscle tissue and is tightly controlled by the peroxisome proliferator-activated receptor-γ co-activator 1 (PGC-1) signaling network. In the present study, we hypothesized that inactivation of glycogen synthase kinase (GSK)-3β, previously suggested to interfere with PGC-1 in non-muscle cells, potentiates PGC-1 signaling and the development of mitochondrial biogenesis during myogenesis, ultimately resulting in an enhanced myotube oxidative capacity.

树木年轮 δ13C 值及其对我国北方大气CO2浓度变化的指示意义

 本文采样分析了承德市油松年轮中δ13C值自工业革命以来的变化,用以揭示我国北方大气CO2浓度的变化规律。结果表明：承德市油松年轮中的δ13C值自1810年以来平均下降了0.839‰,下降范围0.682‰～1.120‰,指示了大气CO2浓度逐渐升高的特点。δ13C值与历史时期全球大气CO2浓度之间存在显著相关关系(r＝ –0.5609,P<0.01)。应用树木年轮δ13C值与大气CO2浓度之间的关系式,推测出我国北方大气CO2浓度从工业革命以前的约278.4μmol·mol-1上升到目前的340μmol·mol-1。从而为我国的全球变化研究提供了CO2浓度历史变迁方面的证据。     

Histidine residues at the active site of maize δ-aminolevulinic acid dehydratase

Modification of maize δ-aminolevulinic acid dehydratase (ALAD) by diethylpyrocarbonate (DEP) caused rapid and complete inactivation of the enzyme. The inactivation showed saturation kinetics with a half inactivation time at saturating DEP equal to 0.3 min and K_DEP  0.3 mM. Substrate δ-aminolevulinic acid (ALA) and competitive inhibitor levulinic acid protected against inactivation, thereby indicating that DEP modifies the active site. The modified enzyme showed an increase in absorbance at 240 nm which was lost upon treatment with 0.8 M hydroxylamine. Most of the activity lost by DEP treatment could be restored after treatment with 0.8 M hydroxylamine. The results suggest that DEP modifies 7.4 residues/mole of the enzyme. These histidine residues are essential for catalysis by ALAD.     

The structures of 9-hydroxyzinnolides and their rearranged acetates

Eleman-8β,12-olides containing a β-hydroxyl group at C-9 exist in equilibrium with 8β-hydroxyeleman-9,12-olides. Acetylation of 9β-hydroxyelemanolides gave a mixture of 8β-and 9β-acetyl derivatives in which the former predominates. The structures of zinaflorin II acetate, zinaflorin III and other 9β-hydroxyelemanolide acetates have been revised. The absolute stereochemistry of the δ-lactone juniperin has been established by means of an X-ray crystallographic analysis.     

Phospholipid binding properties and functional characterization of a sea urchin phospholipase Cdelta in urchin and mouse eggs

We recently identified a novel phospholipase Cdelta isoform, PLC-deltasu, in sea urchin gametes, whose precise functional role during fertilization and early embryogenesis remains unknown. Here, we characterized the binding of the PLC-deltasu PH domain to different phosphatidylinositol (PI) phospholipids and studied changes in its localization during fertilization. The PLC-deltasu PH domain bound most strongly to PI(3,4)P(2) and PI(3,5)P(2) phospholipids, in contrast to the PLCdelta1 PH domain which bound predominantly to PI(4,5)P(2). A green fluorescent protein tagged PLC-deltasu PH domain localized to the plasma membrane and its localization increased at fertilization and following addition of a Ca(2+) ionophore. However, recombinant PLC-deltasu failed to cause Ca(2+) signals like those seen at fertilization, in mouse and sea urchin eggs. Our findings suggest that PLC-deltasu is unlikely to be directly involved in the process of egg activation but may play a role in mediating extracellular signals transmitted via the PI 3'-kinase pathway.