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A Chlorella sp. was isolated from a brackish water high-altitude lake of the Northern-Western Himalayas and selected on the basis of its ability to secrete substantial amount of exopolysaccharide (EPS). The purified EPS was estimated to have molecular weight (Mw) of approximately 1.52 × 105 Da with polydispersity of 2.315 and showed amorphous dense morphology. The production of the EPS was maximized to ≅ 460 mg L−1 through nutrient optimisation. The monosaccharide composition of EPS showed the presence of hexose (glucose, galactose mannose), pentose (xylose, arabinose), deoxy (rhamnose), amino (galactosamine) and acid (galacturonic acid and glucuronic) sugars. The one-dimensional proton NMR and FT-IR analysis confirmed the presence of aliphatic groups. The pseudo-plastic rheology and the antioxidant activity of the EPS suggested its suitability for industrial applications. Importantly, the isolated polysaccharide exhibits its potential for easy and single pot biosynthesis of polysaccharide-capped gold-nanoparticles (AuNPs). The polysaccharide-capped AuNPs displayed exceptional stability at extended pH range and high salinity and suggest that this algal EPS can be utilized for its biotechnological application.

Chinese cabbage (Brassica campestris L. ssp. pekinensis) is a widely cultivated vegetable crop in eastern Asia. The flavor of Chinese cabbage was mostly affected by soluble sugar content. To make clear its accumulation and regulation mechanism, the content of different sugars in the internal blade (IB), the internal midrib (IM), the external blade (EB) and the external midrib (EM) of the leafy head were determined during the leafy head formation. The results showed that fructose was the major sugar accumulated in the internal tissues, followed by glucose. IM was the main tissue of sugar accumulation with the highest contents of total soluble sugar and hexose at harvest. RNA sequencing data of the four tissues at 90 DAS showed that the number of differentially expressed genes (DEGs) in IB and IM was the least (2408), while the number of DEGs between the external and internal tissues ranged from 6037 to 8674. The enzyme genes differentially expressed in ‘starch and sucrose metabolism’ pathway was detected during the leafy head development. The expression of two sucrose synthase (SUS) genes, SUS1a (Bra002332) and SUS1b (Bra006587), were always higher in IM than in the other tissues, and positively correlated with the content of total soluble sugar and hexose, respectively. SUS1 was considered to play an important role in leafy head development and sugar accumulation in Chinese cabbage.

Stereoisomeric hexoses are present in almost all biological organisms in the forms of aldoses and ketoses, with diverse physiological and pathophysiological functions. Accurate and simultaneous quantification is vital for understanding their functions individually. However, such analysis remains challenging owing to their highly similar behavior in chromatography and mass spectrometry. By combining the pre-column 3-nitrophenylhydrazine derivatization and ultrahigh performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS), here, we developed a method for simultaneous quantification of five important stereoisomeric hexoses including D-glucose, D-galactose, D-mannose, D-fructose and L-sorbose representing both aldoses and ketoses. The method achieved baseline-separation for all these five derivatized hexoses chromatographically and had high sensitivity (LOD, femtomole on column), excellent linearity (R2 > 0.995) and efficiency with stable-isotope dilution. With this method, we further quantified these hexoses in nine biological matrices including human biofluids (serum, urine and saliva), human cells, human and mouse feces, rat liver tissue, mung-bean seeds and peach pulp. The results provided quantitative data for these hexoses in multiple biological samples and showed significant concentration diversity for these hexoses in different biological samples, which demonstrated the applicability of the method for simultaneous quantification of these hexose phenotypes of biological systems. • An optimized UHPLC-MS/MS method based on 3-nitrophenylhydrazine derivatization. • Simultaneous quantification of five stereoisomeric hexoses. • Quantitative results for these five hexoses in nine different biological matrices.

Shading and drought stresses during the flowering stage of maize (Zea mays L.) production cause seed losses, making them two of the major limitations to yield output. The mechanisms by which the two stresses reduce seed numbers are still unclear. Here, different durations of shading and different degrees of drought were applied, accompanied by synchronous pollination, and the early development of fertilized apical kernels was suppressed, with decreases in sucrose and hexose levels and the promotion of ethylene emission. Consequently, the two distinct stresses led to a common consequence: up to 20–30% of the fertilized kernels were aborted at maturity, which accounted for the yield losses under both scenarios. Notably, by removing the shading net or the preventing pollination of the basal kernels, the apical kernels, were partial or fully restored from abortion, with an increased sugar status and suppressed ethylene emission, even under stress conditions. We found that dry matter accumulation within the early stage was positively correlated with sucrose and hexose contents but negatively correlated with ethylene emission. By altering the sugar status within developing kernels, we verified the antagonistic relationships between endogenous ethylene emission and soluble sugars, including sucrose and hexoses. Collectively, these findings suggest that the equilibrium between sugars and ethylene may determine the development or abortion of early developing kernels exposed to environmental stresses.

Pollen tubes require a high amount of sugars to sustain high growth rate. Sucrose, the main transport form of sugars, can serve as energy supply and as signaling molecules for pollen tube growth. We report the functional characterization of CsHT11, which is a sugar transporter protein/hexose transport protein (STP/HT). CsHT11 shares high homology with the characterized cucumber hexose transporter CsHT1, a pollen-specific gene. Analysis of CsHT11 mRNA and CsHT11 promoter-reporter gene studies revealed CsHT11 specifically expressed in pollen and pollen tubes. Subcellular localization indicated that CsHT11 is a plasma membrane transporter. Heterologous expression in yeast suggests that CsHT11 is an energy-dependent hexose/H+ symporter, with a wide variety of substrate specificity, including glucose, fructose, galactose, and mannose. In vitro pollen germination of different sugars shows that the expression of CsHT11 is significantly increased with higher sucrose content, but not with higher glucose or fructose content, thereby implying that CsHT11 may be involved in sucrose signal transduction. Thus, CsHT11 might have an essential effect on pollen development and pollen tube growth in cucumber.

Nostoc microscopicum an effective extracellular polymers (EPs) synthesizer among cyanobacteria was isolated, and its elementary morphological features were defined with the aid of light microscope and CLSM. Bioseparation of EPs from 44 days-aged culture gave 0.90 g/L of the dry powdered extract. Chemical quantification of EPs showed the presence of 550 mg/g of carbohydrate and 395 mg/g of protein. HPLC results depicted the presence of mannose (monomer sugar), fucose (hexose deoxy sugar), mannitol (sugar alcohol) and N- acetylglucosamine (glycoprotein) in the EPs. The vibration-based spectrum produced by FT-IR proves the β-Sheet structure of EPs glycoprotein and the size as 45 kDa by performing SDS-PAGE. Bactericidal activity evaluation of EPs on Pseudomonas aeruginosa and Staphylococcus aureus co-expressed the MIC value as 125 μg/mL, while zone of inhibition was 12 mm for Gram-negative and 8 mm for Gram-positive bacteria. Biofilm inhibition assay was effective in 1.0 mg/mL concentration of EPs in both bacterial strains with a mean rate of 60 percentages which was further confirmed using confocal laser scanning microscopic imaging. This natural polymeric extract of Nostoc microscopicum indicates its possible applications in bactericidal and biofilm inhibition.

Background Cellulose is not only a common component in vascular plants, but also has great economic benefits for paper, wood, and industrial products. In addition, its biosynthesis is highly regulated by carbohydrate metabolism and allocation in plant. MdFRK2, which encodes a key fructokinase (FRK) in apple, showed especially high affinity to fructose and regulated carbohydrate metabolism. Results It was observed that overexpression of MdFRK2 in apple decreased sucrose (Suc) and fructose (Fru) with augmented FRK activity in stems, and caused the alterations of many phenotypic traits that include increased cellulose content and an increase in thickness of the phloem region. To further investigate the involved mechanisms, we generated FRK2-OE poplar lines OE#1, OE#4 and OE#9 and discovered (1) that overexpression of MdFRK2 resulted in the huge increased cellulose level by shifting the fructose 6-phosphate or glucose 6-phsophate towards UDPG formation, (2) a direct metabolic pathway for the biosynthesis of cellulose is that increased cleavage of Suc into UDP-glucose (UDPG) for cellulose synthesis via the increased sucrose synthase (SUSY) activity and transcript levels of PtrSUSY1, (3) that the increased FRK activity increases the sink strength overall so there is more carbohydrate available to fuel increased cambial activity and that resulted in more secondary phloem. These results demonstrated that MdFRK2 overexpression would significantly changes the photosynthetic carbon flux from sucrose and hexose to UDPG for increased cellulose synthesis. Conclusions The present data indicated that MdFRK2 overexpression in apple and poplar changes the photosynthetic carbon flux from sucrose and hexose to UDPG for stem cellulose synthesis. A strategy is proposed to increase cellulose production by regulating sugar metabolism as a whole.

Hexokinase (HXK) catalyses hexose phosphorylation and senses glucose signalling to control carbon partition in plants. In sugarcane, HXK is involved in regulating source/sink carbon balance. However, the characteristics of sugarcane HXK genes remain unclear. This study revealed that the full-length cDNA sequence of the HXK gene ShHXK8 cloned from sugarcane mature leaves contains a 1560 bp open reading frame and encodes a putative protein of 519 amino acids. Amongst HXKs from monocot and dicot subjected to phylogenetic analysis, ShHXK8 was clustered into a monocot-specific group with OsHXK7, SbHXK8 and ZmHXK1. Gene expression analysis in Saccharum spp. hybrid ROC22 plants showed that ShHXK8 was expressed in leaves and stalks and expressed highly in mature leaves and young internodes. The difference in the expression of ShHXK8 was compared in high-sugar-content (HSC) and low-sugar-content (LSC) Saccharum officinarum plants. The expression of ShHXK8 in the leaves and internodes 3–24 of HSC plants was lower than that of LSC plants. The expression of ShHXK8 in the internodes 1–2 of HSC plants was higher than that of LSC plants. ShHXK8–GFP fusion was located in the cytosol by transiently expressing the corresponding vectors in rice mesophyll protoplasts. ShHXK8 might function as a cytoplasmic hexokinase involved in hexose metabolism in sugarcane mature leaves and young internodes.

Over-express galactokinase (Galk1) in tissue plasminogen activator (tPA) producing CHO cells as a potential strategy to improve cell growth and product synthesis. tPA producing CHO cells were transfected with the galactokinase (Galk1) gene. CHO-Galk1 cells showed a 39% increase of the specific growth rate in galactose. Moreover, clones were able to use this hexose as their main carbon source to sustain growth contrary to their parental cell line. Metabolic Flux Analysis revealed that the CHO-Galk1 selected clone shows an active metabolism towards biomass and product synthesis, characterized by higher fluxes in the TCA cycle, which is consistent with increased cellular densities and final product concentration. This cellular engineering strategy, where modifications of key points of alternative carbon sources metabolism lead to an improved metabolism of these sugars, is a starting point towards the generation of new cell lines with reduced lactate synthesis and increased cell growth and productivity.

Industrial production of lignocellulosic ethanol requires a microorganism utilizing both hexose and pentose, and tolerating inhibitors. In this study, a hydrolysate-cofermenting Saccharomyces cerevisiae strain was obtained through one step in vivo DNA assembly of pentose-metabolizing pathway genes, followed by consecutive adaptive evolution in pentose media containing acetic acid, and direct screening in biomass hydrolysate media. The strain was able to coferment glucose and xylose in synthetic media with the respective maximal specific rates of glucose and xylose consumption, and ethanol production of 3.47, 0.38 and 1.62 g/g DW/h, with an ethanol titre of 41.07 g/L and yield of 0.42 g/g. Industrial wheat straw hydrolysate fermentation resulted in maximal specific rates of glucose and xylose consumption, and ethanol production of 2.61, 0.54 and 1.38 g/g DW/h, respectively, with an ethanol titre of 54.11 g/L and yield of 0.44 g/g. These are among the best for wheat straw hydrolysate fermentation through separate hydrolysis and cofermentation.

Background Caldicellulosiruptor kronotskyensis has gained interest for its ability to grow on various lignocellulosic biomass. The aim of this study was to investigate the growth profiles of C. kronotskyensis in the presence of mixtures of glucose–xylose. Recently, we characterized a diauxic-like pattern for C. saccharolyticus on lignocellulosic sugar mixtures. In this study, we aimed to investigate further whether C. kronotskyensis has adapted to uptake glucose in the disaccharide form (cellobiose) rather than the monosaccharide (glucose). Results Interestingly, growth of C. kronotskyensis on glucose and xylose mixtures did not display diauxic-like growth patterns. Closer investigation revealed that, in contrast to C. saccharolyticus, C. kronotskyensis does not possess a second uptake system for glucose. Both C. saccharolyticus and C. kronotskyensis share the characteristics of preferring xylose over glucose. Growth on xylose was twice as fast (μmax = 0.57 h−1) as on glucose (μmax = 0.28 h−1). A study of the sugar uptake was made with different glucose–xylose ratios to find a kinetic relationship between the two sugars for transport into the cell. High concentrations of glucose inhibited xylose uptake and vice versa. The inhibition constants were estimated to be KI,glu = 0.01 cmol L−1 and KI,xyl = 0.001 cmol L−1, hence glucose uptake was more severely inhibited by xylose uptake. Bioinformatics analysis could not exclude that C. kronotskyensis possesses more than one transporter for glucose. As a next step it was investigated whether glucose uptake by C. kronotskyensis improved in the form of cellobiose. Indeed, cellobiose is taken up faster than glucose; nevertheless, the growth rate on each sugar remained similar. Conclusions C. kronotskyensis possesses a xylose transporter that might take up glucose at an inferior rate even in the absence of xylose. Alternatively, glucose can be taken up in the form of cellobiose, but growth performance is still inferior to growth on xylose. Therefore, we propose that the catabolism of C. kronotskyensis has adapted more strongly to pentose rather than hexose, thereby having obtained a specific survival edge in thermophilic lignocellulosic degradation communities.

Lilium sargentiae E.H. Wilson (Liliaceae) is an ornamental and economic flowering bulb in China. Unfortunately, due to low natural bulb multiplication rates or long juvenile phases, commercial release of a new genotype may take 10 or even 20 years. In this study, bulbs were expanded in test tubes by adding sucrose, to shorten the duration of the commercial production cycle. Results indicated that when sucrose, with a concentration of 60 g l−1, was supplied to the culture medium, the bulblets could be most effectively induced and expanded. The effect of sucrose on the formation and expansion of L. sargentiae was obvious and dominant. It was not connected to the osmotic potential of sucrose, nor entirely explained by the function of sucrose as an energy and carbon source. We used sugar analogues in the culturing of explanted materials to research the effect of sucrose-specific signaling on bulblet formation and expansion. Results showed that exogenous 3-O-methyl glucose could not induce and expand test-tube bulblets, which was similar to mannose, whereas isomaltulose could generate similar results to those obtained with sucrose. The results further indicated that the specific signalling of sucrose could be responsible for the effect on bulblets formation and swelling. We used the exclusion method to confirm above results and hypothesis, and observed that only a small part of sucrose was transformed by cell wall invertase and entered the cells through hexose transporters, playing a certain effect on bulbelt growth and development through hexose or hexose signaling systems. Overall, the effect of sucrose on bulblet induction and swelling could be explained by sucrose-specific signaling. Furthermore, this effect has a direct correlation with the sucrose-specific vector.

Lactobacilli are involved in fermentation of milk-, plant-, or meat-based food products. They metabolize hexose sugars to lactic acid during fermentation, leading to a decrease in the pH. This preservative effect contributes to the digestibility of the raw material and improves the organo leptic properties of the product. Food fermentations are widely utilized in modern food production, with lactobacilli as defined starter cultures, specifically in the production of fermented raw sausages or milk products.

Substantial amounts of fructose are present in our diet. Unlike glucose, this hexose cannot be metabolized by most cells and has first to be converted into glucose, lactate or fatty acids by enterocytes, hepatocytes and kidney proximal tubule cells, which all express specific fructose-metabolizing enzymes. This particular metabolism may then be detrimental in resting, sedentary subjects; however, this may also present some advantages for athletes. First, since fructose and glucose are absorbed through distinct, saturable gut transporters, co-ingestion of glucose and fructose may increase total carbohydrate absorption and oxidation. Second, fructose is largely metabolized into glucose and lactate, resulting in a net local lactate release from splanchnic organs (mostly the liver). This 'reverse Cori cycle' may be advantageous by providing lactate as an additional energy substrate to the working muscle. Following exercise, co-ingestion of glucose and fructose mutually enhance their own absorption and storage.

Background Seed germination is a crucial process in the plant life cycle when a dramatic variation of type and sugar content occurs just as the seed is hydrated. The production of hexose 6 phosphate is a key node in different pathways that are required for a successful germination. Hexokinase (HXK) is the only plant enzyme that phosphorylates glucose (Glc), so it is key to fueling several metabolic pathways depending on their substrate specificity, metabolite regulatory responses and subcellular localization. In maize, the HXK family is composed of nine genes, but only six of them (ZmHXK4–9) putatively encode catalytically active enzymes. Here, we cloned and functionally characterized putative catalytic enzymes to analyze their metabolic contribution during germination process. Results From the six HXKs analyzed here, only ZmHXK9 has minimal hexose phosphorylating activity even though enzymatic function of all isoforms (ZmHXK4–9) was confirmed using a yeast complementation approach. The kinetic parameters of recombinant proteins showed that ZmHXK4–7 have high catalytic efficiency for Glc, fructose (Fru) and mannose (Man), ZmHXK7 has a lower Km for ATP, and together with ZmHXK8 they have lower sensitivity to inhibition by ADP, G6P and N-acetylglucosamine than ZmHXK4–6 and ZmHXK9. Additionally, we demonstrated that ZmHXK4–6 and ZmHXK9 are located in the mitochondria and their location relies on the first 30 amino acids of the N-terminal domain. Otherwise, ZmHXK7–8 are constitutively located in the cytosol. HXK activity was detected in cytosolic and mitochondrial fractions and high Glc and Fru phosphorylating activities were found in imbibed embryos. Conclusions Considering the biochemical characteristics, location and the expression of ZmHXK4 at onset of germination, we suggest that it is the main contributor to mitochondrial activity at early germination times, at 24 h other ZmHXKs also contribute to the total activity. While in the cytosol, ZmHXK7 could be responsible for the activity at the onset of germination, although later, ZmHXK8 also contributes to the total HXK activity. Our observations suggest that the HXKs may be redundant proteins with specific roles depending on carbon and ATP availability, metabolic needs, or sensor requirements. Further investigation is necessary to understand their specific or redundant physiological roles. Electronic supplementary material The online version of this article (10.1186/s12870-018-1605-x) contains supplementary material, which is available to authorized users.

Background l-Fucose (Fuc), a six-deoxy hexose monosaccharide, is present endogenously in humans and animals and has a wide range of biological functions. In the present study, we aimed to examine the effect of Fuc on obesity and hepatic steatosis in mice fed a high-fat diet (HFD). Methods C57BL/6 mice were fed a normal chow (NC) or HFD for 18 weeks to induce obesity and fatty liver. Fuc was administered intragastrically from the 8th week to the end of the experiment (18 weeks). Results Metagenomic analysis showed that HFD altered the genomic profile of gut microbiota in the mice; specifically, expression of alpha-l-fucosidase, the gene responsible for Fuc generation, was markedly reduced in the HFD group compared with that in the NC group. Fuc treatment decreased body weight gain, fat accumulation, and hepatic triglyceride elevation in HFD-fed mice. In addition, Fuc decreased the levels of endotoxin-producing bacteria of the Desulfovibrionaceae family and restored HFD-induced enteric dysbiosis at both compositional and functional levels. Conclusion Our findings suggest that Fuc might be a novel strategy to treat HFD-induced obesity and fatty liver.

The capacity to co-transport glucose and xylose into yeast has remained a technical challenge in the field. While significant efforts have been made in transporter engineering to increase xylose transport rates, glucose-based inhibition still limit most of these transporters. To address this issue, we further engineer sugar transporter proteins to remove glucose inhibition and enable glucose/xylose co-transport. Specifically, we start with our previously derived CiGXS1 FIM mutant strain and subjugate it to several rounds of mutagenesis and selection in a hexose metabolism null strain. Through this effort, we identify several mutations including N326H, a truncation in the C-terminal tail, I171F, and M40V as additionally dominant for reducing glucose inhibition. The resulting transporter shows substantially improved xylose transport rates in the presence of high quantities of glucose including up to 70 g/L glucose. Moreover, the resulting transporter enables co-utilization of glucose and xylose with glucose rates on par with a wild-type transporter and xylose rates exceeding that of glucose. These results demonstrate that major facilitator superfamily hexose transporters can be rewired into glucose-xylose co-transporters without functional inhibition by either substrate. These results enhance the potential of using lignocellulosic biomass as a feedstock for yeast.

Aiming at creation of the chemical basis for serotyping of strains of Yersinia spp., we studied the O-specific polysaccharide (OPS) of Yersinia frederiksenii H56-36/81 belonging to serotype O:60. A branched polysaccharide was obtained by mild alkaline degradation of the lipopolysaccharide (LPS) isolated from bacterial cells by the phenol—water extraction and found to contain d-ribose, l-rhamnose, and 4-deoxy d-arabino-hexose (d-ara4dHex). The last monosaccharide occurs rarely in nature and earlier has been found only in OPS of Citrobacter spp. Mild acid hydrolysis of the LPS resulted in cleavage of the d-ara4dHex side-chains to give a linear polysaccharide. Structure of the hexasaccharide repeating unit of the OPS was established by studies of both isolated polysaccharides by 1D and 2D 1H and 13C NMR spectroscopy.

Immunospecificity of gram-negative bacteria, including Escherichia coli, is defined by the fine structure of the O-specific polysaccharide chain of the lipopolysaccharide called O-antigen. Structures of the O-antigens have been established for the majority of about 200 known serotypes of E. coli but serotype O162 was among few that have not been studied in this respect yet. In the present work, it was found that bacteria of this serotype produce several O-polysaccharides differing in the main chains composed of N-acetylglucosamine and N-acetylgalactosamine residues as well as in the presence or absence of side-chain 4-deoxy-D-arabino-hexose residues. It was also shown that E. coli O101 produces two linear O-polysaccharides, which are structurally similar to the main chains of E. coli O162, whereas only one of them had been identified in these bacteria earlier.

Pectin-rich biomasses, such as citrus peel and sugar beet pulp, hold promise as inexpensive feedstocks for microbial fermentations as enzymatic hydrolysis of their component polysaccharides can be accomplished inexpensively to yield high concentrations of fermentable sugars and d-galacturonic acid (d-galUA). In this study, we tackle a number of challenges associated with engineering a microbial strain to convert pectin-rich hydrolysates into commodity and specialty chemicals. First, we engineer d-galUA utilization into yeast, Saccharomyces cerevisiae. Second, we identify that the mechanism of d-galUA uptake into yeast is mediated by hexose transporters and that consumption of d-galUA is inhibited by d-glucose. Third, we enable co-utilization of d-galUA and d-glucose by identifying and expressing a heterologous transporter, GatA, from Aspergillus niger. Last, we demonstrate the use of this transporter for production of the platform chemical, meso-galactaric acid, directly from industrial Navel orange peel waste., Pectin-rich agricultural byproducts are ideal feedstocks for biobased chemicals production. Here, the authors engineer the yeast, S. cerevisiae, in several steps to co-utilize d-galacturonic acid and d-glucose and demonstrate the potential of producing meso-galactaric acid from industrial orange peel.

To determine Monod kinetics parameters (µmax, Ks, kd and YX/S) of the mesophilic H2 producer Clostridium termitidis grown on glucose and cellobiose by modeling in MATLAB.Maximum specific growth rates (µmax) were 0.22 and 0.24 h(-1) for glucose and cellobiose respectively; saturation constants (Ks) were 0.17 and 0.38 g l(-1) respectively and the biomass yields (YX/S) were 0.26 and 0.257 g dry wt g(-1) substrate. H2 yields of 1.99 and 1.11 mol H2 mol(-1) hexose equivalent were also determined for glucose and cellobiose respectively.The microbial kinetics of this model microorganism will enhance engineering biofuel production applications.

In yeast, the hexose assimilation is started at hexose phosphorylation. However, in Kluyveromyces marxianus, the hexokinase (HXK) and glucokinase (GLK) genes were not identified by experiments. Meanwhile, the glucose-free fructose product requires more cost-efficient method. In this study, the KmHXK1 and KmGLK1 genes were functionally identified through gene disruption, over-expression and recombinant enzymes characterization. Both glucose and fructose assimilation ability decreased significantly in KmHXK1 disrupted strain YLM001, however, this ability was not changed obviously in KmGLK1 disrupted strain YLM002. When over-expressing KmGLK1 in YLM001, only the glucose assimilation ability was recovered in obtained strain (YLM005). The kinetic constant analysis of recombinant enzymes also proved that KmHXK1 could phosphorylate glucose (Vmax 553.01 U/mg, Km 0.83 mM) and fructose (Vmax 609.82 U/mg, Km 0.52 mM), and KmGLK1 only phosphorylate glucose with a Vmax of 0.73 U/mg and a Km 4.09 mM. A thermo-tolerant strain YGR003 which produced glucose-free fructose from Jerusalem artichoke tuber in one step was constructed based on the obtained information. The highest production and fastest productivity were 234.44 g/L and 10.26 g/L/h, respectively, which were several folds of the results in previous reports.

The accumulation level of soluble carbohydrates in fibers during flowering may affect the final fiber length in upland cotton (Gossypium hirsutum L.). The objective of this study was to determine the relationship of carbohydrate levels and carbon metabolism enzyme activities in fibers to fiber elongation under water deficit stress. A pot study was conducted in 2013 with treatments consisting of control (well-watered) and water stress using two cotton genotypes differing in drought tolerance, namely S011 (drought sensitive) and T886 (drought tolerant). Water stress treatment was designed as withholding water from the pots until stomatal closure followed by limited water supply for 25 days where water-stressed plants received 40% of optimum quantity of water. The results showed that the glucose, fructose, sucrose and starch concentrations decreased in water-stressed fibers compared to the control. The degree of decline in hexose and total soluble sugar concentrations under water deficit stress was higher in the sensitive genotype (S011) than the tolerant genotype (T886). Similar changes were also observed in vacuolar invertase (VIN) and sucrose synthase (SuSy) activities. The reduction in hexose concentration might be due to decreased sucrose-cleaving enzyme activities especially VIN activity. The study showed that drought stress decreased VIN and SuSy activities, and hence hexose concentration in fiber cells, which resulted in a slower fiber elongation compared to the control.

Background The glucose dual-affinity transport system (low- and high-affinity) is a conserved strategy used by microorganisms to cope with natural fluctuations in nutrient availability in the environment. The glucose-sensing and uptake processes are believed to be tightly associated with cellulase expression regulation in cellulolytic fungi. However, both the identities and functions of the major molecular components of this evolutionarily conserved system in filamentous fungi remain elusive. Here, we systematically identified and characterized the components of the glucose dual-affinity transport system in the model fungus Neurospora crassa. Results Using RNA sequencing coupled with functional transport analyses, we assigned GLT-1 (K m = 18.42 ± 3.38 mM) and HGT-1/-2 (K m = 16.13 ± 0.95 and 98.97 ± 22.02 µM) to the low- and high-affinity glucose transport systems, respectively. The high-affinity transporters hgt-1/-2 complemented a moderate growth defect under high glucose when glt-1 was deleted. Simultaneous deletion of hgt-1/-2 led to extensive derepression of genes for plant cell wall deconstruction in cells grown on cellulose. The suppression by HGT-1/-2 was connected to both carbon catabolite repression (CCR) and the cyclic adenosine monophosphate-protein kinase A pathway. Alteration of a residue conserved across taxa in hexose transporters resulted in a loss of glucose-transporting function, whereas CCR signal transduction was retained, indicating dual functions for HGT-1/-2 as “transceptors.” Conclusions In this study, GLT-1 and HGT-1/-2 were identified as the key components of the glucose dual-affinity transport system, which plays diverse roles in glucose transport and carbon metabolism. Given the wide conservation of the glucose dual-affinity transport system across fungal species, the identification of its components and their pleiotropic roles in this study shed important new light on the molecular basis of nutrient transport, signaling, and plant cell wall degradation in fungi. Electronic supplementary material The online version of this article (doi:10.1186/s13068-017-0705-4) contains supplementary material, which is available to authorized users.

High fructose consumption has been implicated with deleterious effects on human health, including hyperlipidemia elicited through de novo lipogenesis. However, more global effects of fructose on cellular metabolism have not been elucidated. In order to explore the metabolic impact of fructose-containing nutrients, we applied both GC-TOF and HILIC-QTOF mass spectrometry metabolomic strategies using extracts from cultured HepG2 cells exposed to fructose, glucose, or fructose + glucose. Cellular responses were analyzed in a time-dependent manner, incubated in media containing 5.5 mM glucose + 5.0 mM fructose in comparison to controls incubated in media containing either 5.5 mM glucose or 10.5 mM glucose. Mass spectrometry identified 156 unique known metabolites and a large number of unknown compounds, which revealed metabolite changes due to both utilization of fructose and high-carbohydrate loads independent of hexose structure. Fructose was shown to be partially converted to sorbitol, and generated higher levels of fructose-1-phosphate as a precursor for glycolytic intermediates. Differentially regulated ratios of 3-phosphoglycerate to serine pathway intermediates in high fructose media indicated a diversion of carbon backbones away from energy metabolism. Additionally, high fructose conditions changed levels of complex lipids toward phosphatidylethanolamines. Patterns of acylcarnitines in response to high hexose exposure (10.5 mM glucose or glucose/fructose combination) suggested a reduction in mitochondrial beta-oxidation.

The effect of low temperature on sugar content and activities of key enzymes related to sucrose metabolism in grape (Vitis vinifera L.) branches during overwintering covered with soil was investigated. We measured the contents of soluble sugar and the activities of sucrose-phosphate synthase (SPS), sucrose synthase (SS), acid invertase (AI) and neutral invertase (NI) of three grape varieties with different freezing tolerance, Beta, Vidal and Merlot, in October, 2011, January, 2012 and March, 2012. The result showed that: total soluble sugar had the significant negative correlation, −0.988, with temperature during overwintering covered with soil. The content of hexose was about twofold content of sucrose in January, while sucrose increased and the hexose decreased to a very low level in March, the ratios between hexose and sucrose declined to 0.26, 0.15 and 0.18. Sucrose was more important than hexose in protecting grape branches from cold injury under low temperature, but non-freezing. The accumulation of sucrose was mostly due to the elevation of the SPS activity, whereas the increase of hexose was due to the enhanced AI activity. Three grape varieties responded to low temperature positively as reflected by the variations of physiological and biochemical characteristics, such as superoxide dismutase, catalase and proline. Besides, by the principal components analysis and combined with cultivation practices, among twelve characteristics, the sugar metabolism mainly contributed to the difference of the cold resistance. The results indicated that sucrose metabolism regulation played an important role during overwintering covered with soil, and it was the key factor to explain the difference of cold resistance.

The accuracy of several commonly used methods for glucose measurement in the presence of tea polyphenols (TPLs) was investigated since TPLs (as a representative of bioactive polyphenols) and glucose often co-exist in experiments exploring TPLs’ effect on carbohydrate metabolism. The results from a model system containing only glucose and TPLs showed a TPLs’ amount-dependent variation of measured glucose concentration with a relative error (RE) of 5.0% to 35.5% when a dinitrosalicylic acid (DNS) method was used, and for glucose oxidase/peroxidase assay, the results showed a decreased content of glucose with a RE from 56.7% to 102.7%. When a hexose/kinase (HK) method was employed to quantify the glucose content, the accuracy (RE from 0.57% to 4.7%) was comparable to the result obtained by a high performance liquid chromatography (HPLC) method (RE = 0.7–3.0%) that was used as the standard control. Starch digestion experiment further demonstrated the invalidity of DNS method and the accuracy of HK method. Thus, the HK method with its accuracy and convenience is the preferred method for glucose measurement in the presence of TPLs or other bioactive polyphenols.

A Sporobolomyces spp. (strain O33) was isolated from soil as a potential resource for producing microbial oil from carbohydrates. This microbe produced intracellular lipids from various carbohydrates, such as hexose, pentose, and polysaccharides. Major fatty acids found in the lipids were C18:1 (36–55%), C16:0 (18–29%), and C18:2 (15–28%), and these were clearly distinct from those produced by Lipomyces, Rhodotorula, and Yarrowia spp. Preliminary examination of lipid formation with an optimized C:N ratio resulted in a yield of 1.65 g/l and a lipid content of 50%. These results suggest that Sporobolomyces strain O33 has a potential application in the mass production of single cell oil.

Soluble acid invertase (SAI, EC 3.2.1.26), catalyzes the hydrolysis of sucrose into hexose sugars, and it has been considered a key enzyme for carbohydrate metabolism. In the present study, the activity of SAI enzyme was determined to establish a correlation between the change in transcript levels and enzyme activity in high and low sugar accumulating sugarcane cultivars, in various internodal tissues at different developmental stages. A decrease in SAI activity and transcript levels was observed with age, during all the developmental stages in both the cultivars. A negative correlation between SAI activity and sucrose content was observed in mature and immature internodes; however, there was a positive correlation between SAI activity and content of hexose sugars. These results imply that SAI plays a crucial role in sucrose partitioning in various intermodal tissues in high and low sugar cultivars. In addition to this, the changes in enzyme activity also resulted in changes in transcript level.

We identified and characterized two genes, LAT1 and LAT2, which encode specific L: -arabinose transporters. The genes were identified in the L: -arabinose fermenting yeast Ambrosiozyma monospora. The yeast Saccharomyces cerevisiae had only very low L: -arabinose transport activity; however, when LAT1 or LAT2 was expressed, L: -arabinose transport was facilitated. When the LAT1 or LAT2 were expressed in an S. cerevisiae mutant where the main hexose transporters were deleted, the L: -arabinose transporters could not restore growth on D: -glucose, D: -fructose, D: -mannose or D: -galactose. This indicates that these sugars are not transported and suggests that the transporters are specific for L: -arabinose.

The white-rot basidiomycetes, Peniophora cinerea and Trametes suaveolens, can produce ethanol from hexoses. Although T. suaveolens produced negligible amounts of ethanol under aerobic conditions, P. cinerea produced ethanol under both aerobic and semi-aerobic conditions and assimilated glucose, mannose, fructose, galactose, sucrose, maltose and cellobiose with yields of ethanol of 0.41, 0.45, 0.44, 0.19, 0.41, 0.44 and 0.45 g per g hexose, respectively. The corresponding results for T. suaveolens were 0.39, 0.3, 0.13, 0.2, 0.37, 0.35 and 0.31 g ethanol/g hexose. Furthermore, P. cinerea exhibited simultaneous saccharification and fermentation of amorphous cellulose.

Sugarcane cultivars with a high (susceptible cultivars) and low (resistant cultivars) virus titer of Sugarcane yellow leaf virus were grown in the field. The carbohydrate composition in green leaf tops and in stems was determined. In RT-PCR of leaf extracts, susceptible cultivars had a high SCYLV-titer, whereas resistant cultivars had a very low titer. The cultivars differed in biomass yield, but these differences were not correlated with susceptibility. However, carbohydrate composition did have susceptibility-specific differences. Hexose levels were lower in green leaf tops and stalks of susceptible (strongly infected) cultivars than in those of resistant (weakly infected) cultivars. The stalks of susceptible cultivars also had less starch than those of resistant cultivars. Thus, the viral susceptibility (and infection) affected sugar metabolism. In addition, a positive correlation between hexose and starch in stems and between hexose and sucrose in green leaf tops was observed. The results from susceptible versus resistant cultivars were the opposite of those in the comparison between infected versus virus-free lines of the same cultivar. The breeding process apparently had unintentionally selected clones with modulated carbohydrate metabolism to avoid or compensate for the adverse effects of SCYLV infection.

The use of lignocellulose as a source of sugars for bioproducts requires the development of biocatalysts that maximize product yields by fermenting mixtures of hexose and pentose sugars to completion. In this study, we implicate mgsA encoding methylglyoxal synthase (and methylglyoxal) in the modulation of sugar metabolism. Deletion of this gene (strain LY168) resulted in the co-metabolism of glucose and xylose, and accelerated the metabolism of a 5-sugar mixture (mannose, glucose, arabinose, xylose and galactose) to ethanol.

We investigated the effects of prolonged hypoxia on the sugar uptake in tomato (Solanum lycopersicum L. var. MP-1) roots. Hydroponic cultures of whole tomato plants were submitted to hypoxic treatment for 1 week, and the roots were analyzed for sugar concentrations, hexose uptake and hexose transporter expression level. Contrary to what has been observed after anoxic shock or short-term hypoxic treatment, we show that sugar concentrations increase and hexose uptake is up-regulated in the roots after 1 week of hypoxic treatment. Increased hexose transport is concomitant with the induction of the hexose transporter gene LeHT2. These responses may be due either to a direct effect of low O2 supply, or to a secondary effect associated with the increase in sugar concentrations, which, typically, develops in most hypoxic plants.

A variety of metabolites are routinely assayed after perchloric acid extraction of plant tissues. A common technique uses coupled enzyme assays that produce or consume pyridine nucleotides together with spectrophotometric detection at 340 nm. Because of the presence of pigments in plant tissues, the high absorbance of such extracts usually limits the amount of extract that can be assayed spectrophotometrically. Here, we show that after batch adsorption with AG50WX8 (H+ form), the absorbance of potato root perchloric acid extracts at 340 nm is significantly reduced. This clean up procedure does not interfere with the assay or the recovery of anionic metabolites such as hexose phosphates. It therefore facilitates spectrophotometric assays of metabolites in plant extracts with high absorbance.

Expression and function of hexose transporters vary diurnally in rat small intestine; however, this subject remains unexplored in mice.The aim of the study was to investigate the diurnal expression and function of hexose transporters SGLT1, GLUT2, and GLUT5 in mouse small bowel.Twenty-four c57bl6 mice maintained in a 12-h light/dark room (6 AM: -6 PM: ) were sacrificed at 9 AM: , 3 PM: , 9 PM: , and 3 AM: (n = 6 each). In duodenal, jejunal, and ileal mucosa, total cellular mRNA and protein levels were quantitated by real-time PCR and semiquantitative Western blotting, respectively. The everted sleeve technique measured transporter-mediated glucose uptake at 9 AM: and 9 PM: .mRNA expression of SGLT1, GLUT2, and GLUT5 varied diurnally in all three intestinal segments (por= 0.03). SGLT1, GLUT2, and GLUT5 protein levels varied diurnally in duodenum and jejunum (p0.05) but not in ileum. Transporter-mediated glucose uptake was greater at 9 PM: than 9 AM: (por= 0.04) in all three segments. V (max) was greater in duodenum (10 vs 6 nmol/cm/s) and jejunum (8 vs 5 nmol/cm/s) at 9 PM: compared to 9 AM: (p = 0.01); K (m) remained unchanged. mRNA levels of intestinal hexose transporters varied diurnally. Protein levels peaked 6-12 h later during dark cycle when70% of food intake occurred; glucose transport followed a similar pattern with increased uptake at 9 PM: .Hexose transporter expression and function vary diurnally with nocturnal feeding patterns of mice.

The hexose transmembrane transporters SGLT1 and GLUT2 are present in low quantities in ileum where little glucose absorption occurs normally; however, glucose uptake in ileum is highly adaptable after small bowel resection.Ileal adaptability for glucose absorption after jejunal resection is mediated predominately by upregulation of GLUT2.Rats underwent 70% proximal-based jejunoileal resection. Transporter-mediated glucose uptake was measured in proximal and distal remnant ileum 1 and 4 wk postoperatively (n = 6 rats, each) and in corresponding ileal segments in control and 1 wk sham laparotomy rats (n = 6, each) without and with selective inhibitors of SGLT1 and GLUT2. In separate groups of rats (n = 6, each), protein (Western blots), mRNA (reverse transcriptase polymerase chain reaction [RT-PCR]), and villus height (histomorphology) were measured.After 70% proximal intestinal resection, there was no dramatic change in protein or mRNA expression per cell of either SGLT1 or GLUT2, but median glucose uptake (nmol/cm/min) increased markedly from 52 (range 28-63) in controls to 118 (range 80-171) at 1 wk, and 203 (range 93-248) at 4 wk (por = 0.04 each) correlating with change in villus height (por = 0.03).Ileal adaptation for glucose transport occurs through cellular proliferation (hyperplasia) and not through cellular upregulation of glucose transporters.

Five unusual hexose derivatives were isolated from the carbohydrate portion of the solid-state fermentation extract of Actinosynnema pretiosum ssp. auranticum ATCC 31565, which is a producing strain of maytansinoids that are a family of 19-membered macrocyclic lactams having extraordinary cytotoxic and antineoplastic activities. Their structures were determined to be 2-deoxy-α-D-arabino-hexopyranose (1), 2-deoxy-β-D-arabino-hexopyranose (2), 3,6-anhydro-2-deoxy-α-D-arabino-hexcofuranose (3), 3,6-anhydro-2-deoxy-β-D-arabino-hexofuranose (4), and 2-(D-glycerol-1,2-dihydroxyethyl)furan (5) by NMR spectroscopic experiments.

A novel beta-galactosidase of 120 kDa (BgaBM) from Bacillus megaterium 2-37-4-1 was purified, and its gene (bgaBM) was analyzed and expressed. It displayed wide acceptor specificity for transglycosylation with a series of acceptors, including pentose, hexose, hydroxyl, and alkyl alcohol using o-nitrophenyl-beta-D-galactoside (ONPG) as a donor. BgaBM preferentially hydrolyzed ONPG in all tested substrates and showed maximum activity at pH 7.5-8.0 and 55 degrees C. It was stable at pH 6.0-9.0 below 40 degrees C. The K(m) and V(max) values for ONPG and lactose were 9.5 mM, 16.6 mM/min and 12.6 mM, 54.4 mM/min, respectively. The nucleotide sequence of the bgaBM gene consists of an ORF of 3,105 bp corresponding to 118 kDa protein, which indicates that BgaBM is a modular enzyme in the glycosyl hydrolase family 2, including conserved sugar-binding domain, acid-base catalyst, and immunoglobulin-like beta-sandwich domain. The possible acid/base and nucleophile sites of BgaBM were estimated to be E481 and E547, respectively. Furthermore, expression of the bgaBM gene in Escherichia coli and purification of the recombinant enzyme were performed. The recombinant enzyme showed similar biochemical characteristics to natural enzyme.

We investigated the effects of a gibberellin synthesis inhibitor (ancymidol) and gibberellin (GA4+7) on carbohydrate metabolism and elongation in internodes of the tulip (Tulipa gesneriana L.) flower stalk during greenhouse growth. During the initial stages of flower stalk growth, the lowermost internode was mainly responsible for total flower stalk length, whereas the uppermost internode mostly contributed to total length during later stages. High concentrations of hexose sugar (mainly glucose) and increased activity of acid invertase were observed when internodes were rapidly elongating. Inhibition of gibberellin biosynthesis with ancymidol reduced the elongation rate of internodes, and inhibited the hexose sugar accumulation and acid invertase activity. Application of GA4+7 to ancymidol-treated plants reversed these effects. The degree of response to ancymidol and GA4+7 was, however, different in different internodes such that the lowermost internode was most responsive and the uppermost internode was least responsive. The results indicate that de novo biosynthesis of gibberellins is a requirement for expression of high acid invertase activity during the rapid elongation phase in tulip internodes which enables cleavage of imported sucrose to hexoses that can be readily utilized in elongating cells.

A short root mutant was isolated from an EMS-generated rice mutant library. Under normal growth conditions, the mutant exhibited short root, delayed flowering, and partial sterility. Some sections of the roots revealed that the cell length along the longitudinal axis was reduced and the cell shape in the root elongation zone shrank. Genetic analysis indicated that the short root phenotype was controlled by a recessive gene. Map-based cloning revealed that a nucleotide substitution causing an amino acid change from Gly to Arg occurred in the predicted rice gene (Os02g0550600). It coded an alkaline/neutral invertase and was homologous to Arabidopsis gene AtCyt-inv1. This gene was designated as OsCyt-inv1. The results of carbohydrate analysis showed an accumulation of sucrose and reduction of hexose in the Oscyt-inv1 mutant. Exogenously supplying glucose could rescue the root growth defects of the Oscyt-inv1 mutant. These results indicated that OsCyt-inv1 played important roles in root cell development and reproductivity in rice.

To investigate the effect of mannose on lipopolysaccharide (LPS) induced acute lung injury (ALI) in rats.Ten groups of Sprague-Dawley rats were used: 1) the control group received an intratracheal instillation of saline, 2) the LPS group received an intratracheal instillation of LPS (3 mg/kg), 3-6) the mannose groups were injected i.v. with 15, 45, 135, and 405 mg/kg mannose, 7-9) the glucose, galactose, and fructose groups were injected with different hexoses (135 mg/kg), and 10) the dexamethasone (DXM) group was injected with DXM (2 mg/kg). In groups 2-8, LPS was administered after injection of drugs. Lung wet/dry weight ratio, permeability index (PPI), total leukocytes and polymorphonuclear neutrophils (PMNs) counts in bronchoalveolar lavage fluid (BALF), myeloperoxidase (MPO) and superoxide dismutase (SOD) activity, tumor necrosis factor (TNF)-alpha and interleukin (IL)-10 in lung and BALF were determined.Pre-treatment with mannose attenuated pulmonary edema and protein exudation in a dose-dependent manner, the maximal effect was similar to or greater than that of DXM. Mannose also prevented the inflammatory cell accumulation, although the maximal effect was weaker than that of DXM. Mannose was more effective than DXM in inhibiting MPO activity and restoring SOD activity. Moreover, it inhibited production of TNF-alpha and IL-10. Histological changes of the lungs were also ameliorated by mannose. There were no significant improvements observed in rats pre-treated with glucose, galactose or fructose.Mannose is effective in reducing LPS-induced ALI.

Earlier studies have shown a correlation between the presence of a 77 kDa protein in the proteins extracted from young adult Drosophila melanogaster (D.m.) and the autosomal longevity allele. A2 at the JmA locus. In this study, a 77 kDa protein has been isolated from pupae of D.m. of a long-lived strain of genotype A2A2, and was purified by DEAE chromatography, ConA column chromatography, and two cycles of gel filtration. The purified protein has a molecular weight of 76,600 (by SDS-PAGE), an isoelectric point of pH 6.5, and molar extinction coefficient A(280(1%) = 18.3. It is a glycoprotein containing 3.3% hexose. Supplementing the food of D.m. with the purified protein at 5 x 10(-4) micrograms/ml, beginning at day 5 after emergence, resulted in an increase in the survival rate and maximal life span of both short-lived and long-lived strains of D.m.

The effects of sodium chloride on the degradation of hexoses at 220 °C and the hydrolysis of sucrose at 170 °C in subcritical water were examined. Sodium chloride accelerated the degradation at 220 °C of any hexose, especially the degradation of galactose which significantly accelerated depending on the sodium chloride concentration. On the other hand, the hydrolysis of sucrose at 170 °C was not affected by sodium chloride.

Asr genes are exclusively found in the genomes of higher plants. In many species, this gene family is expressed under abiotic stress conditions and during fruit ripening. The encoded proteins have nuclear localisation and consequently a transcription factor function has been suggested. Interestingly, yeast-one-hybrid experiments revealed that a grape ASR binds to the promoter of a hexose transporter gene (VvHT1). However, the role of these proteins in planta is still elusive. By using a reverse genetics approach in potato we found that modification of Asr1 expression has no incidence on the aerial phenotype of the plant but exerts a dramatic effect in tuber. Asr1 antisense potatoes displayed decreased tuber fresh weight whereas Asr1 overexpressors had a diminished number of tubers. Moreover, overexpression lines showed lower transcript levels of a plasma membrane hexose transporter and a concomitant decrease in glucose content in parenchyma cells of potato tubers. On the same hand glucose uptake rate was also reduced in one of the overexpressing lines. It thus seems likely that Asr1 is involved in the control of hexose uptake in heterotrophic organs. In addition, the transgenic plants were characterized by several other changes in steady state metabolite levels. Results presented here support a role for ci21A/Asr1 in glucose metabolism of potato tuber.

Background Management of infection is a major clinical problem. Staphylococcus aureus is a Gram-positive bacterium which colonises approximately one third of the adult human population. Staphylococcal infections can be life-threatening and are frequently complicated by multi-antibiotic resistant strains including methicillin-resistant S. aureus (MRSA). Fluorodeoxyglucose ([18F]FDG) imaging has been used to identify infection sites; however, it is unable to distinguish between sterile inflammation and bacterial load. We have modified [18F]FDG by phosphorylation, producing [18F]FDG-6-P to facilitate specific uptake and accumulation by S. aureus through hexose phosphate transporters, which are not present in mammalian cell membranes. This approach leads to the specific uptake of the radiopharmaceutical into the bacteria and not the sites of sterile inflammation. Methods [18F]FDG-6-P was synthesised from [18F]FDG. Yield, purity and stability were confirmed by RP-HPLC and iTLC. The specificity of [18F]FDG-6-P for the bacterial universal hexose phosphate transporter (UHPT) was confirmed with S. aureus and mammalian cell assays in vitro. Whole body biodistribution and accumulation of [18F]FDG-6-P at the sites of bioluminescent staphylococcal infection were established in a murine foreign body infection model. Results In vitro validation assays demonstrated that [18F]FDG-6-P was stable and specifically transported into S. aureus but not mammalian cells. [18F]FDG-6-P was elevated at the sites of S. aureus infection in vivo compared to uninfected controls; however, the increase in signal was not significant and unexpectedly, the whole-body biodistribution of [18F]FDG-6-P was similar to that of [18F]FDG. Conclusions Despite conclusive in vitro validation, [18F]FDG-6-P did not behave as predicted in vivo. However at the site of known infection, [18F]FDG-6-P levels were elevated compared with uninfected controls, providing a higher signal-to-noise ratio. The bacterial UHPT can transport hexose phosphates other than glucose, and therefore alternative sugars may show differential biodistribution and provide a means for specific bacterial detection.

Transfer cell formation in cotyledons of developing faba bean (Vicia faba L.) seeds coincides with an abrupt change in seed apoplasm composition from one dominated by hexoses to one in which sucrose is the principal sugar. On the basis of these observations, we tested the hypothesis that sugars induce and/or sustain transfer cell development. To avoid confounding effects of in planta developmental programs, we exploited the finding that adaxial epidermal cells of cotyledons, which do not become transfer cells in planta, can be induced to form functional transfer cells when cotyledons are cultured on an agar medium. Growth rates of cotyledons cultured on hexose or sucrose media were used to inform choice of sugar concentrations. The same proportion of adaxial epidermal cells of excised cotyledons were induced to form wall ingrowths independent of sugar species and concentration supplied. In all cases, induction of wall ingrowths coincided with a marked increase in the intracellular sucrose-to-hexose ratio. In contrast, further progression of wall ingrowth deposition was correlated positively with intracellular sucrose concentrations that varied depending upon external sugar species and supply. Sucrose symporter induction and subsequent maintenance behaved identically to wall ingrowth formation in response to an external supply of hexoses or sucrose. However, in contrast to wall ingrowth formation, induction of sucrose symporter activity was delayed. We discuss the possibility of intracellular sugars functioning both as signals and substrates that induce and control subsequent development of transfer cells.

Symbiotic nitrogen fixation (SNF) in legume nodules is a highly energy demanding process, fuelled by plant-supplied carbohydrates mainly in the form of sucrose. In this study, we have combined molecular and biochemical approaches in order to study the spatial and temporal organisation of sucrose metabolism in nitrogen-fixing nodules of the model legume Lotus japonicus, with an emphasis on the neglected role of alkaline/neutral invertase. For this purpose, a full-length cDNA clone coding for an alkaline/neutral invertase isoform, termed LjInv1, was identified in a L. japonicus mature nodule cDNA libraries. Alkaline/neutral invertase activity was also found to be the predominant invertase activity in mature nodules. Real-time reverse-transcription polymerase chain reaction analysis was used in order to study the temporal expression patterns of LjInv1 in parallel with genes encoding acid invertase and sucrose synthase (SuSy) isoforms, and enzymes involved in the subsequent hexose partitioning including hexokinase, phosphoglucomutase (PGM) and phosphoglucose isomerase (PGI). The spatial organisation of sucrose metabolism was studied by in situ localisation of LjInv1 transcripts and alkaline/neutral invertase activity, and SuSy protein during nodule development. Furthermore, the spatial organisation of hexose metabolism was investigated by histochemical localisation of hexokinase, PGM and PGI activities in mature nodules. The results considered together indicate that alkaline/neutral invertase could contribute to both the Glc-1-P and Glc-6-P pools in nodules, fuelling both biosynthetic processes and SNF. Furthermore, transcript profiling analysis revealed that genes coding for hexokinase and putative plastidic PGM and PGI isoforms are upregulated during the early stages of nodule development, while the levels of transcripts corresponding to cytosolic PGM and PGI isoforms remained similar to uninfected roots, indicating a possible role of LjInv1 in producing hexoses for starch production and other biosynthetic processes in developing nodules.

To further elucidate the mechanisms underlying carbon-partitioning in plants, we established an experimental system by generating transgenicArabidopsis lines that overexpress both the fructose 6-phosphate, 2-kinase (F6P,2-K) and the fructose 2,6-bisphosphatase (F26BPase) domains. We also produced knockout transgenic plants for these domains via RNAi and T-DNA tagging. In F6P,2-K overexpressing transgenics, F6P,2-K activity increased slightly and Fru-2,6-P2 levels were elevated by 80%, compared with the wild type (WT). F26BPase activity was similar between the WT and transgenic plants. However, when that domain was overexpressed, F26BPase activity was increased by 70% compared with the WT, whereas F6P,2-K activity was reduced to 85% of the WT level. In knockout and RNAi mutant lines that showed reduced F6P,2-K and F26BPase activities, levels of Fru-2,6-P2 were only between 3 to 7% of those for the WT. In F6P,2-K overexpressing transgenic lines, the levels of starch, hexose, and triose phosphates slightly increased, while sucrose content was marginally reduced. In F26BPase overexpressing plants, however, the levels of soluble sugars and hexose phosphates were slightly increased, but starch and triose phosphate contents declined. Furthermore, compared with the WT, the levels of soluble sugars rose while starch and hexose phosphate quantities decreased in 2-kinase/fructose-2,6-bisphophatase knockout mutants. Therefore, our data reaffirms that Fru-2,6-P2 contributes to the regulation of photosynthetic carbon-partitioning between starch and sucrose inArabidopsis leaves by limiting sucrose synthesis.

Background A RIL population between Solanum lycopersicum cv. Moneymaker and S. pimpinellifolium G1.1554 was genotyped with a custom made SNP array. Additionally, a subset of the lines was genotyped by sequencing (GBS). Results A total of 1974 polymorphic SNPs were selected to develop a linkage map of 715 unique genetic loci. We generated plots for visualizing the recombination patterns of the population relating physical and genetic positions along the genome. This linkage map was used to identify two QTLs for TYLCV resistance which contained favourable alleles derived from S. pimpinellifolium. Further GBS was used to saturate regions of interest, and the mapping resolution of the two QTLs was improved. The analysis showed highest significance on Chromosome 11 close to the region of 51.3 Mb (qTy-p11) and another on Chromosome 3 near 46.5 Mb (qTy-p3). Furthermore, we explored the population using untargeted metabolic profiling, and the most significant differences between susceptible and resistant plants were mainly associated with sucrose and flavonoid glycosides. Conclusions The SNP information obtained from an array allowed a first QTL screening of our RIL population. With additional SNP data of a RILs subset, obtained through GBS, we were able to perform an in silico mapping improvement to further confirm regions associated with our trait of interest. With the combination of different ~ omics platforms we provide valuable insight into the genetics of S. pimpinellifolium-derived TYLCV resistance. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-1152) contains supplementary material, which is available to authorized users.