Effect of abscisic acid (ABA) on sugar accumulation in the flesh tissue of peach fruit at the start of the maturation stage

Experiments were conducted on¹⁴C-sorbitol, fructose, and glucose uptakeinto flesh discs, and sorbitol efflux from thediscs, with and without ABA application toexamine the effect of abscisic acid (ABA) onsugar accumulation in peach fruit flesh at thestart of the maturation stage in relation tomembrane transport. Total uptake of¹⁴C-sorbitol, fructose, and glucose intoflesh discs was effectively promoted by ABA ata concentration of 10^–5 M. PCMBS(p-chloromercuribenzensulfonicacid)-sensitive uptake, which was considered ascarrier-mediated uptake, of sorbitol into thediscs was clearly stimulated by ABA at10^–5 M, compared with glucose andfructose uptake. Sorbitol efflux from the discsacross the tonoplast was restricted by ABA at10^–5 M. ABA application todeveloping fruit increased sugar accumulationin the fruit. Estimated ABA concentration inthis fruit was approximately 10^–5 M. These results indicate that sugar accumulationin peach fruit flesh is stimulated by ABA at aconcentration of 10^–5 M both invitro and in vivo. ABA stimulatesuptake of sugars, especially sorbitol, into theflesh by enhancing carrier-mediated transportpossibly across both tonoplast and plasmamembrane.     

Biosynthetic studies on the alpha-glucosidase inhibitor acarbose: the chemical synthesis of dTDP-4-amino-4,6-dideoxy-alpha-D-glucose

To study the biosynthesis of the pseudotetrasaccharide acarbose, dTDP-4-amino-4,6-dideoxy-alpha-D-glucose (3) was prepared from galactose in 16 steps. After initial protecting-group manipulations, the 6-position of galactose was deoxygenated by hydride displacement of a tosylate. Similarly a tosyl group at the 4-position was displaced upon reaction with sodium azide. Conversion of the resulting glycoside to a glycosyl phosphate was accomplished by reaction of a glycosyl trichloroacetimidate with dibenzyl phosphate. Subsequent removal of the benzyl protecting groups and reduction of the azide by hydrogenation and coupling with an activated nucleoside phosphate gave dTDP-4-amino-4,6-dideoxy-alpha-D-glucose.     

基于葡萄EST数据库糖代谢途径有关基因的分析

以拟南芥糖代谢相关酶基因序列作为探针,对葡萄EST数据库进行同源检索筛选,获得相应的同源EST序列,并以葡萄果实cDNA为模板,通过PCR反应,对葡萄糖代谢途径相关基因进行了分析。进一步预测了葡萄糖代谢途径相关酶编码基因个数,分别位于1、4、5、6、7、8、11、12、13、16、17、18、19号染色体,另有3条序列未能定位到染色体,并对编码基因表达强弱进行了分析,为深入了解葡萄果实内糖代谢的机理提供一定的工作基础,也可以为如何调控果实糖代谢以及提高葡萄果实品质提供理论依据。     

The iodosulfonamidation of peracetylated glycals revisited: access to 1,2-di-nitrogenated sugars

Iodosulfonamidation of peracetylated glycals was investigated using either a combination of N-iodosuccinimide/iodine or iodine chloride as a source of iodonium ion. 1,2-trans- and 1,2-cis-2-deoxy-2-iodo-1-sulfonamido hexoses were, respectively, obtained depending on the reagent system used. Both series of isomers were successfully converted to 1,2-di-nitrogenated compounds, for example, 1-azido-1,2-dideoxy-2-sulfonamido sugars, which are useful intermediates for the synthesis of N-linked glycoproteins or glycoconjugates.     

The amino‐terminal tail of Hxt11 confers membrane stability to the Hxt2 sugar transporter and improves xylose fermentation in the presence of acetic acid

Hxt2 is a glucose repressed, high affinity glucose transporter of the yeast Saccharomyces cerevisiae and is subjected to high glucose induced degradation. Hxt11 is a sugar transporter that is stably expressed at the membrane irrespective the sugar concentration. To transfer this property to Hxt2, the N‐terminal tail of Hxt2 was replaced by the corresponding region of Hxt11 yielding a chimeric Hxt11/2 transporter. This resulted in the stable expression of Hxt2 at the membrane and improved the growth on 8% d ‐glucose and 4% d ‐xylose. Mutation of N361 of Hxt11/2 into threonine reversed the specificity for d ‐xylose over d ‐glucose with high d ‐xylose transport rates. This mutant supported efficient sugar fermentation of both d ‐glucose and d ‐xylose at industrially relevant sugar concentrations even in the presence of the inhibitor acetic acid which is normally present in lignocellulosic hydrolysates. Biotechnol. Bioeng. 2017;114: 1937–1945. © 2017 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc.     

烤烟糖含量的空间变异特征

以中国烤烟(Nicotiana tabacum)主产省份2005年B2F(上部二级桔黄色烤烟)、C3F(中部三级桔黄色烤烟)和X2F(下部二级桔黄色烤烟)3个等级烤烟为研究对象,利用地统计学与GIS技术结合的方法研究了中国烤烟主产省份烤烟水溶性总糖、还原糖含量和糖碱比的空间分布特征。结果表明:各等级烤烟水溶性总糖、还原糖含量和糖碱比空间相关性表现为近似相关,东西方向上,均呈现由西向东先降低后升高的趋势,南北方向上,水溶性总糖含量、还原糖含量趋势不明显,糖碱比各等级趋势各异。     

Some preliminary results on the action of rhamnogalacturonase on rhamnogalacturonan oligosaccharides from beet pulp

Sugar-beet pulp was saponified and then hydrolysed with 0.1 M HCI at 80°C for 72 h, and a rhamnogalacturonan fraction was isolated by ion-exchange chromatography on AG 1X8 resin. Four individual oligomers, and a mixture of oligomers with higher degrees of polymerization, were obtained by chromatography on BioGel P-4. They all presented the -d-GalAp-(1 [→2)--l-Rhap-(1 → 4)--d-GalAp-(1]_n→2)-l-Rhap structure (with n 2) The five fractions were submitted to hydrolysis with rhamnogalacturonase. The enzyme was active on oligomers with degrees of polymerization f10, and gave as main products -l-Rhap-(1 → 4)--d-GalAp-(1 → 2)--l-Rhap(1 → 4)-d-GalAp and -d-GalAp-(1 → 2)--l- Rhap- (1 → 4) --d- GalAp- (1 → 2) --l-Rhap-(1 → 4)-d-GalAp.     

苹果果实糖积累特性与品质形成的关系

以'富士'和'国光'苹果为研究对象,对其果实发育过程中糖含量及其代谢关键酶活性的变化进行测定分析,以揭示糖分积累代谢特性对果实品质形成的影响.结果表明:(1)'富士'和'国光'均为己糖积累型果实, '富士'果实以积累果糖最多,果糖/葡萄糖(F/G)值为1.56,而'国光'以积累葡萄糖最多,F/G值仅为0.68;蔗糖在两品种中含量和所占比例均很低,在近成熟期'富士'高于'国光'.(2)'富士'果实蔗糖磷酸合成酶(SPS)和蔗糖合成酶(SS)活性均随果实糖的累积量增加而显著升高,酸性转化酶(AI)活性也渐趋升高,而中性转化酶(NI)活性波动不大,且其糖累积与AI和SPS活性相关性最大,而与NI相关性不大,SS的作用主要表现在发育后期;在 '国光'果实糖积累过程中SPS起主导作用,SS和NI的作用主要表现在发育前期,而AI的作用不大.(3)'富士'和'国光'果实淀粉含量变化趋势相同,在淀粉积累高峰之后,'富士'果实淀粉降解速度更快,其淀粉含量迅速下降且低于'国光',此时其相应淀粉酶活性也高于'国光'.研究发现,'富士'和'国光'果实糖积累和淀粉代谢均存在显著差异,从而直接或间接地影响着果实糖代谢过程,进而导致果实品质的显著差异.     

Effect of conformation and configuration of arabinose residues on the circular dichroism of C-glycosylflavones

Examination of a variety of arabinose containing C-glycosylflavones has shown that the sign and intensity of the CD band at 250–275 nm (charge-transfer band) reflect not only the point of attachment of the sugar to the flavone but also depend upon the absolute and anomeric configuration, ring-size and ring-conformation in addition to the preferred rotameric conformation of the sugar about the C-aryl, C-l″ bond. A change in stereochemistry of arabinose from the α to β anomer resulted in sign inversion of the 250–275 nm CD band for 6-C-l-arabinosylflavones. Furthermore, a 6-C-arabinosylflavone containing α-l-arabinose exhibited an oppositely signed charge-transfer CD band in comparison to one which contained α-d-arabinose. 6,8-Di-C-glycosylflavones containing arabinose and glucose exhibited CD bands resulting from contributions due to both sugars, if the arabinose was not present as the β-pyranose form (¹C₄, conformation).     

紫外辐射增强对植物糖代谢的影响

综述了UV-B辐射增强对植物叶片、茎、根、果实以及籽粒中糖含量影响的研究现状与动态,从生理学角度分析了UV-B辐射对植物糖含量和糖代谢相关的一些重要反应及其影响植物糖含量和糖代谢的关键酶的响应,并从植物的光合碳固定、糖的合成与分解等方面阐述了UV-B影响糖含量及糖代谢的可能机理。展望了今后紫外辐射增强对植物糖代谢影响的研究重点和研究方向。     

Carbohydrate starvation is a major determinant of the loss of greening capacity in cotyledons of dark-grown sugar beet seedlings

The transition of cotyledons from heterottophy to autotrophy is a critical step of seedling establishment. We have studied the greening capacity of sugar beet ( Beta vulgaris L. cv. Véga) cotyledons in relation to carbohydrate and energy metabolism during dark growth. During early growth, sugar beet cotyledons behaved mainly as a lipid-mobilizing and gluconeogenic tissue providing substrates to the seedling. Reserve mobilization was followed by a maximum of the adenine nucleotide pool on day 6 in strict correlation with the maximum of greening capacity. This was immediately followed by the onset of a typical situation of carbohydrate starvation characterized by substrate limitation of respiration, a decrease in the adenine nucleotide pool and, as shown by the respiratory quotient and the loss of proteins, a probable utilization of cellular proteins and lipids to sustain respiration. The conversion from etioplast to chloroplast, as determined by the rate of chlorophyll synthesis, was less and less efficient as carbohydrate starvation continued, finally leading to incomplete and heterogeneous greening on day 12. The relationship of the loss of greening capacity with carbohydrate starvation is discussed.     

The Arabidopsis SUCROSE UNCOUPLED-6 gene is identical to ABSCISIC ACID INSENSITIVE-4: involvement of abscisic acid in sugar responses

In plants, sugars act as signalling molecules that control many aspects of metabolism and development. Arabidopsis plants homozygous for the recessive sucrose uncoupled-6 (sun6) mutation show a reduced sensitivity to sugars for processes such as photosynthesis, gene expression and germination. The sun6 mutant is insensitive to sugars that are substrates for hexokinase, suggesting that SUN6 might play a role in hexokinase-dependent sugar responses. The SUN6 gene was cloned by transposon tagging and analysis showed it to be identical to the previously described ABSCISIC ACID INSENSITIVE-4 (ABI4) gene. Our analysis suggests the involvement of abscisic acid and components of the abscisic acid signal transduction cascade in a hexokinase-dependent sugar response pathway. During the plant life cycle, SUN6/ABI4 may be involved in controlling metabolite availability in an abscisic acid- and sugar-dependent way.     

Mutational analysis of the sugar-binding site of pea lectin

Comparison of x-ray crystal structures of several legume lectins, co-crystallized with sugar molecules, showed a strong conservation of amino acid residues directly involved in ligand binding. For pea (Pisum sativum) lectin (PSL), these conserved amino acids can be classified into three groups: (I) D81 and N125, present in all legume lectins studied so far; (II) G99 and G216, conserved in almost all legume lectins; and (III) A217 and E218, which are only found in Vicieae lectins and are possibly determinants of sugar-binding specificity. Each of these amino acids in PSL was changed by site-directed mutagenesis, resulting in PSL molecules with single substitutions: for group I D81A, D81N, N125A; for group II G99R, G216L; and for group III A217L, E218Q, respectively. PSL double mutant Y124R; A126S was included as a control. The modified PSL molecules appeared not to be affected in their ability to form dimeric proteins, whereas the sugar-binding activity of each of the PSL mutants, with the exception of the control mutant (as shown by haemagglutination assays), was completely eliminated. These results confirm the model of the sugar-binding site of Vicieae lectins as deduced from X-ray analysis.     

Application of a reaction model to improve calculation of the sugar recovery standard for sugar analysis

A kinetic model was applied to improve determination of the sugar recovery standard (SRS) for biomass analysis. Three sets of xylose (0.10-1.00 g/L and 0.999-19.995 g/L) and glucose (0.206-1.602 g/L) concentrations were measured by HPLC following reaction of each for 1 h. Then, parameters in a kinetic model were fit to the resulting sugar concentration data, and the model was applied to predict the initial sugar concentrations and the best SRS value (SRS(p)). The initial sugar concentrations predicted by the model agreed with the actual initial sugar concentrations. Although the SRS(e) calculated directly from experimental data oscillated considerably with sugar concentration, the SRS(p) trend was smooth. Statistical analysis of errors and application of the F-test confirmed that application of the model reduced experimental errors in SRS(e). Reference SRS(e) values are reported for the three series of concentrations.     

A structural study of the asparagine-linked oligosaccharide moiety of duck ovomucoid

Asparagine-linked oligosaccharides of duck ovomucoid were released quantitatively from the protein by digestion with glycoamidase A (from almond), the reducing ends of the oligosaccharide chains thus obtained were aminated with a fluorescent reagent, 2-aminopyridine, and the mixture of pyridylamino derivatives of the oligosaccharides was separated using two different types of high performance liquid chromatography (HPLC) on a reversed phase column and an amide adsorption column. More than sixteen different oligosaccharides were separated and the structures were characterized by a combination of the 2-dimensional sugar mapping technique using HPLC, exoglycosidase digestion, and proton nuclear magnetic resonance measurements (1- and 2-dimensional). Furthermore, the HPLC profile of duck ovomucoid oligosaccharides was compared with previously reported profiles obtained from quail and chicken ovomucoids.Abbreviations COSY chemical shift-correlated spectroscopy - DQF-COSY double quantum filtered COSY - DSS sodium, 4,4-dimethyl-4-silapentane 1-sulfonate - Gal D-galactose - GlcNAc or GN N-acetyl-D-glucosamine - HOHAHA homonuclear Hartmann-Hahn spectroscopy - Man or M D-mannose - NOE nuclear Overhauser enhancement - ODS octadecylsilyl - PA pyridylamino - ROESY rotating frame nuclear Overhauser effect spectroscopy - SDS/PAGE sodium dodecyl sulfate/polyacrylamide gel electrophoresis     

Binding of carbohydrates to solid supports Part 3: Reaction of sugar hydrazones with polystyrene substituted with aromatic aldehydes

The hydrazones of glucose and N-acetylglucosamine, as models for the residues at the reducing termini of glycans, were covalently and reversibly bound in good yield to hydroxybenzaldehydo ligands attached to a polymer support. The binding, by a sugar azine linkage, occurred within two hours at room temperature at neutral pH, and efficient recoveries of sugars from the beads were achieved by displacement with aqueous hydrazine hydrate, ethanolic benzaldehyde, or aqueous acetone. Enzyme modification of glycans was demonstrated by separation of the products of hydrolysis of lactose hydrazone with -galactosidase, using hydroxybenzaldehyde-derivatized polystyrene beads. Addition of a spacer arm to aminopolystyrene beads, for binding of reducing sugars as Amadori compounds to the aromatic amine function, was also investigated.     

秦岭东段不同海拔栓皮栎粗根非结构性碳水化合物含量的季节动态

掌握树木根部碳存储规律对于准确估算碳在地上器官与地下器官间的分配非常必要.本研究以栓皮栎(Quercus variabilis Blume)为对象,在2016年5月-2017年6月,通过周期性采样方法(共计采样14次),测定了高、低海拔(970和650 m)栓皮栎粗根非结构性碳水化合物(non-structural c...     

Synthesis of 3′,4′-difluoro-3′-deoxyribonucleosides and its evaluation of the biological activities: Discovery of a novel type of anti-HCV agent 3′,4′-difluorocordycepin

Upon reacting 3′,4′-unsaturated cytosine (8 and 9) and adenine nucleosides (13 and 14) with XeF₂/BF₃·OEt₂, the respective novel 3′,4′-difluoro-3′-deoxyribofuranosyl nucleosides (10–12 and 15–18) could be obtained. Formation of anti-adducts (11, 16 and 18) revealed that the fluorination involved oxonium ions as incipient intermediates. TBDMS-protected 3′,4′-unsaturated adenosine provided the β-face adducts as sole stereoisomers whereas α-face-selectivity was observed with the TBDPS-protected adenosine 14. The evaluation of the novel 3′-deoxy-3′,4′-difluororibofuranosylcytosine-(19–21) and adenine nucleosides (22–25) against antitumor and antiviral activities revealed that 3′,4′-difluorocordycepin (24) was found to possess anti-HCV activity. The SI of 24 was comparable to that of the anti-HCV drug ribavirin. However, sofosbuvir, FDA-approved novel anti-HCV drug, showed better SI value. Our finding revealed that the introduction of the fluoro-substituent into the 4′-position of cordycepin derivatives decreased the cytotoxicity to the host cell with retention of the antiviral activity.     

Synthesis of Quinoxaline Azido and Amino Reverse Ribofuranoside and Their O-Regioisomers

A series of quinoxaline azido reverse nucleosides 3a-c and their O-regioisomers 4a-c was prepared by reaction of quinoxaline 1a-c with 3-azido-3-deoxy-1,2-O-isopropylidene-5-p-toluenesulfonyl-D-ribofuranose (2) in the presence of sodium hydride. Structure modification of these interesting structures includes reduction and the subsequent acetylation reactions to give quinoxaline amino and acetyl amino reverse nucleosides and their O-regioisomers.