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Yeast metabolizes the disaccharide melibiose by hydrolyzing it into equimolar concentrations of glucose and galactose by MEL1-encoded α-galactosidase. Galactose metabolizing genes (including MEL1) are induced by galactose and repressed by glucose, which are the products of melibiose hydrolysis. Therefore, how melibiose catabolization and utilization take place by circumventing the glucose repression is an enigma. Other than the galactose metabolizing genes MTH1, a negative regulator of glucose signal pathway has Gal4p binding sites and is induced by galactose and repressed by high glucose concentration. But, at low or no glucose MTH1 along with its paralogue STD1 represses hexose transporters, that are involved in glucose transport. This sort of tuning of glucose and galactose regulation motivated us to delineate the role of MTH1 as a regulator of MEL1 expression and melibiose utilization. The deletion mutant of MTH1 shows growth defect on melibiose and this growth defect is enhanced upon the deletion of both MTH1 and its paralogue STD1. Microscopy and flowcytometry analysis, suggest, that even though MEL1 and GAL1 promoter are under Gal4p and Gal80p regulation, upon deletion of MTH1 it hampers only MEL1 expression, but not the GAL1 gene expression. By using 2-Deoxy galactose toxicity assay, we observed phenotypic heterogeneity in cells grown on melibiose i.e. after cleaving of melibiose a fraction of cell population utilizes glucose and another fraction utilizes galactose and coexist together. Understanding GAL/MEL gene expression patterns in melibiose will have great implication to understand various other complex sugar utilizations, tunable gene expressions and complex feedback gene regulations.SignificanceSugar metabolism is an important phenomenon to understand the regulation of gene expression. Glucose is the most preferred carbon source. Yeast follows glycolytic pathways like cancer cells for metabolism of sugars and understanding this will throw more light to the metabolism of cancer cells. In this communication we observed cell-to-cell heterogeneity in yeast cells playing a key role in metabolism of a complex disaccharide melibiose, which gets cleaved into glucose and galactose by α-galactosidase. Glucose represses α-galactosidase and galactose induces it. Because of the heterogeneous population of cells one fraction consumes glucose liberated by melibiose hydrolysis, therefore it is not sufficient to repress α-galactosidase and other GAL genes. Therefore, GAL genes are expressed and help in metabolizing melibiose and galactose.

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.

AMPK/SNF1 is the master regulator of energy homeostasis in eukaryotic cells and has a key role in glucose de-repression. If glucose becomes depleted, Snf1 is phosphorylated and activated. Activation of Snf1 is required but is not sufficient for mediating glucose de-repression indicating a second glucose-regulated step that adjusts the Snf1 pathway. To elucidate this regulation, we further explore the spatial dynamics of Snf1 and Mig1 and how they are controlled by concentrations of hexose sugars. We utilize fluorescence recovery after photobleaching (FRAP) to study the movement of Snf1 and how it responds to external glucose concentrations. We show that the Snf1 pathway reacts both to the presence and to the absolute concentration of glucose. Furthermore, we identify a negative feedback loop regulating Snf1 activity. We also show that Mig1 localization correlates with the Snf1 phosphorylation pattern and not with the Mig1 phosphorylation pattern, suggesting that inactivation of Snf1 has a more pronounced effect on the localization of Mig1 than on the phosphorylation of Mig1. Our data offer insight into the true complexity of regulation of this central signaling pathway by one signal (glucose depletion) interpreted by the cell in different ways.

The degradative condensation of hexose, which originates from the C-C cleavage of hexose and condensation of degraded hexose fragment, is one of the possible reaction pathways for the formation of humins in hexose dehydration to 5-hydroxymethylfurfural (HMF). Herein, the impacts of several polar aprotic solvents on the degradative condensation of fructose to small-molecule carboxylic acids and oligomers (possible precursors of humins) are reported. In particular, a close relationship between the tautomeric distribution of fructose in solvents and the mechanism of degradative condensation is demonstrated. Typically, α-fructofuranose in 1,4-dioxane and acyclic open-chain fructose in THF favor the conversion of fructose to formic acid and oligomers; α-fructopyranose in γ-valerolactone or N-methylpyrrolidone favors levulinic acid and oligomers, whereas β-fructopyranose in 4-methyl-2-pentanone favors acetic acid and corresponding oligomers. This close correlation highlights a general understanding of the solvent-controlled formation of oligomers, which represents an important step toward the rational design of effective solvent systems for HMF production.

Insufficient delivery of oligonucleotides to muscle and heart remains a barrier for clinical implementation of antisense oligonucleotide (AO)-mediated exon-skipping therapeutics in Duchenne muscular dystrophy (DMD), a lethal monogenic disorder caused by frame-disrupting mutations in the DMD gene. We previously demonstrated that hexose, particularly an equal mix of glucose:fructose (GF), significantly enhanced oligonucleotide delivery and exon-skipping activity in peripheral muscles of mdx mice; however, its efficacy in the heart remains limited. Here we show that co-administration of GF with peptide-conjugated phosphorodiamidate morpholino oligomer (PPMO, namely, BMSP-PMO) induced an approximately 2-fold higher level of dystrophin expression in cardiac muscles of adult mdx mice compared to BMSP-PMO in saline at a single injection of 20 mg/kg, resulting in evident phenotypic improvement in dystrophic mdx hearts without any detectable toxicity. Dystrophin expression in peripheral muscles also increased. However, GF failed to potentiate BMSP-PMO efficiency in aged mdx mice. These findings demonstrate that GF is applicable to both PMO and PPMO. Furthermore, GF potentiates oligonucleotide activity in mdx mice in an age-dependent manner, and, thus, it has important implications for its clinical deployment for the treatment of DMD and other muscular disorders. Keywords: hexose, peptide-conjugated morpholino oligomer, Duchenne muscular dystrophy, exon skipping, cardiac functions

Background Candida albicans is an opportunistic commensal microorganism, often associated with severe infections in immunosuppressed individuals. C. albicans has hexose transporters that may favor the intracellular accumulation of photosensitizer (PS). the aims of this study were to investigate the influence of glucose load on photodynamic antimicrobial chemotherapy (PACT); and the role that membrane transport system plays on this therapy in the presence of glucose. Material and methods Strains of C. albicans were selected: ATCC 10231, YEM 12, YEM 13, YEM 14 and YEM 15. All strains were grown aerobically on Sabouraud agar and incubated at 30 °C for 24 h. The strains were treated with and without glucose, and divided into Control (no treatment), LED light (660 nm, 166 mW/cm2), Photosensitizer (100 μM methylene blue) and PACT at 1, 3 and 6 min of irradiation groups. The colony forming units were counted and data submitted to statistical analysis (ANOVA) and Tukey's test. The concentration of methylene blue (MB) outside the yeast was measured by fluorescence spectroscopy. Results PACT inactivate C. albicans and the presence of glucose did not affect the killing effect for most strains. Only YEM12 was partially affected by its presence. Regarding efflux systems, ABC overexpressing strain showed a protective effect on the yeast cells. We observed that yeast with overexpression of major facilitator superfamily (MFS) membrane pore tended to accumulate more MB in its cytoplasm, whereas strains that overexpressed ABC pumps (ATP-binding cassette transporters) tended to decrease MB uptake and survive the photodynamic challenge. Conclusion Presence of glucose showed a small effect on PACT . The accumulation of MB on yeast induces more photodynamic inactivation; however, the photodynamic efficacy depends on the type and characteristics of the microbial strain.

Summary Sugar transporters are necessary to transfer hexose from cell wall spaces into parenchyma cells to boost hexose accumulation to high concentrations in fruit. Here, we have identified an apple hexose transporter (HTs), MdHT2.2, located in the plasma membrane, which is highly expressed in mature fruit. In a yeast system, the MdHT2.2 protein exhibited high 14C‐fructose and 14C‐glucose transport activity. In transgenic tomato heterologously expressing MdHT2.2, the levels of both fructose and glucose increased significantly in mature fruit, with sugar being unloaded via the apoplastic pathway, but the level of sucrose decreased significantly. Analysis of enzyme activity and the expression of genes related to sugar metabolism and transport revealed greatly up‐regulated expression of SlLIN5, a key gene encoding cell wall invertase (CWINV), as well as increased CWINV activity in tomatoes transformed with MdHT2.2. Moreover, the levels of fructose, glucose and sucrose recovered nearly to those of the wild type in the sllin5‐edited mutant of the MdHT2.2‐expressing lines. However, the overexpression of MdHT2.2 decreased hexose levels and increased sucrose levels in mature leaves and young fruit, suggesting that the response pathway for the apoplastic hexose signal differs among tomato tissues. The present study identifies a new HTs in apple that is able to take up fructose and glucose into cells and confirms that the apoplastic hexose levels regulated by HT controls CWINV activity to alter carbohydrate partitioning and sugar content.

The objective of this study was to evaluate the effects of hydraulic retention time (HRT) (8–1 h) on H 2 production from sugarcane juice (5000 mg COD L −1 ) in mesophilic (30 °C, AFBR-30) and thermophilic (55 °C, AFBR-55) anaerobic fluidized bed reactors (AFBRs). At HRTs of 8 and 1 h in AFBR-30, the H 2 production rates were 60 and 116 mL H 2 h −1 L −1 , the hydrogen yields were 0.60 and 0.10 mol H 2 mol −1 hexose, and the highest bacterial diversities were 2.47 and 2.34, respectively. In AFBR-55, the decrease in the HRT from 8 to 1 h increased the hydrogen production rate to 501 mL H 2 h −1 L −1 at the HRT of 1 h. The maximum hydrogen yield of 1.52 mol H 2 mol −1 hexose was observed at the HRT of 2 h and was associated with the lowest bacterial diversity (0.92) and highest bacterial dominance (0.52).

Although hexoses glucose and fructose serve as important energy sources of food, up to now, there is little information about hexose transporters in birds’ intestinal epithelium during their first postnatal week. The aim of the investigation was to carry out an immunohistochemical study of integral membrane proteins glucose transporter-2 and -5 (GLUT-2 and GLUT-5) on intestinal epithelial cells of ostrich chicks during their first postnatal week. The material from duodenum and ileum was collected from 9 female ostriches (Struthio camelus var. Domesticus) divided into three age groups, three birds in each group: chicks immediately after hatching, 3-day-old ostriches and 7-day-old chicks. The material was fixed in 10% formalin, embedded into paraffin, slices 7μm thick were cut followed by immunohistochemical staining with polyclonal primary antibodies Rabbit anti- GLUT-2 and Rabbit anti-GLUT-5, carried out according to the manufacturer’s guidelines (IHC kit, Abcam, UK). Immunohistochemical localization of GLUT-2 and -5 in the intestinal epithelial cells in ostriches of different age groups was determined. In the groups of chicks after hatching and 3-day-old ostriches, enterocytes in duodenal epithelium were mostly unstained and goblet cells stained weakly for both antibodies. Weak staining of enterocytes and goblet cells was also noted in the ileal epithelium of the chick after hatching. Moderate staining of goblet cells was noted in the 3-day-old chicks’ ileal epithelium. In 7-day-old ostriches, the expression of both antibodies was weak in duodenal but moderate in ileal epithelial cells. The pattern of immunohistochemical expression of GLUT-2 and GLUT-5 in ostriches’ intestinal epithelial cells confirms our hypothesis that the intestinal tract of ostriches after hatching is not yet entirely capable of transportation of hexoses and showed that it is completing gradually during the first postnatal week.

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.

Carrageenase is useful for preparation of carrageenan oligosaccharides, which have significant bioactivity. We expressed a κ‑carrageenase gene from Zobellia sp. ZL-4 in full-length (κ-ZL-4) or after truncation of the carbohydrate binding module and the Type-IX secretion module (κ-ZL-4-GH16). κ-ZL-4-GH16 showed a specific activity (134.22 U/mg) 1.93 times higher than that of κ-ZL-4, and its thermal and pH stability also increased. The best activity of κ-ZL-4-GH16 was presented at pH 3.0–6.0, which was lower than the optimal pH of reported κ-carrageenases. The enzyme-substrate affinity of κ-ZL-4-GH16 was higher than that of κ-ZL-4, demonstrated by its lower Michaelis-Menten constant (0.704 mg/mL at pH 6.0). Importantly, κ-ZL-4-GH16 released 10-fold more κ-carrageenan disaccharides than κ-ZL-4. The κ-carrageenan tetrose and hexose produced by the two enzymes were purified and structurally identified. Molecular docking with κ-carrageenan hexose suggested that the efficiency improvement after truncation might be attributed to the conformation differences of the two enzymes.

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.

Silencing expression of SlSWEET1a substantially reduced hexose accumulation in young leaves of tomato plants, revealing the key role of SlSWEET1a in glucose import to sink leaves., Sugar allocation from source to sink (young) leaves, critical for plant development, relies on activities of plasma membrane sugar transporters. However, the key sugar unloading mechanism to sink leaves remains elusive. SWEET transporters mediate sugar efflux into reproductive sinks; therefore, they are promising candidates for sugar unloading during leaf growth. Transcripts of SlSWEET1a, belonging to clade I of the SWEET family, were markedly more abundant than those of all other 30 SlSWEET genes in young leaves of tomatoes. High expression of SlSWEET1a was also detected in reproductive sinks, such as flowers. SlSWEET1a was dominantly expressed in leaf unloading veins, and the green fluorescent protein (GFP) fusion protein was localized to the plasma membrane using Arabidopsis protoplasts, further implicating this carrier in sugar unloading. In addition, yeast growth assays and radiotracer uptake analyses further demonstrated that SlSWEET1a acted as a low-affinity (Km ~100 mM) glucose-specific carrier with a passive diffusion manner. Finally, virus-induced gene silencing of SlSWEET1a expression reduced hexose accumulation to ~50% in young leaves, with a parallel 2-fold increase in mature leaves. Thus, we propose a novel function for SlSWEET1a in the uptake of glucose into unloading cells as part of the sugar unloading mechanism in sink leaves of tomato.

Factorial fermentation experiments on food waste (FW) inoculated with activated sludge (AS) were conducted to investigate the effects of pH and the inoculum-to-substrate ratio (ISR [g VSAS/g TOCFW]) on biohydrogen production. The two parameters affected the H2 yield, the fermentation rate and the biochemical pathways. The minimum and maximum yields were 41 L H2/kg TOCFW (pH = 7.5, ISR = 1.74) and 156–160 L H2/kg TOCFW (pH = 5.5, ISR = 0.58 and 1.74). The range of carbohydrates conversion into H2 was 0.37–1.45 mol H2/mol hexose, corresponding to 9.4–36.2% of the theoretical threshold. A second-order predictive model for H2 production identified an optimum region at low pHs and high ISRs, with a theoretical maximum of 168 L H2/kg TOCFW at pH = 5.5 and ISR = 1.74. The Spearman’s correlation method revealed several relationships between the variables, suggesting the potentially governing metabolic pathways, which turned out to involve both hydrogenogenic pathways and competing reactions.

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.

A procedure has been developed for the synthesis of gold glyconanoparticles with an average particle size of 15–30 nm and a low polydispersity index on the basis of natural hexose (d-glucose, d-galactose, d-mannose) sulfanylacetyl-, 3-sulfanylpropanoyl-, and 2-sulfanylbenzoylhydrazones and thiolated poly(2-deoxy-2-methacryloylamino-d-glucose).

The hexose monophosphate (HMP) shunt acts as an essential component of cellular metabolism in maintaining carbon homeostasis. The HMP shunt comprises two phases viz. oxidative and nonoxidative, which provide different intermediates for the synthesis of biomolecules like nucleotides, DNA, RNA, amino acids, and so forth; reducing molecules for anabolism and detoxifying the reactive oxygen species during oxidative stress. The HMP shunt is significantly important in the liver, adipose tissue, erythrocytes, adrenal glands, lactating mammary glands and testes. We have researched the articles related to the HMP pathway, its metabolites and disorders related to its metabolic abnormalities. The literature for this paper was taken typically from a personal database, the Cochrane database of systemic reviews, PubMed publications, biochemistry textbooks, and electronic journals uptil date on the hexose monophosphate shunt. The HMP shunt is a tightly controlled metabolic pathway, which is also interconnected with other metabolic pathways in the body like glycolysis, gluconeogenesis, and glucuronic acid depending upon the metabolic needs of the body and depending upon the biochemical demand. The HMP shunt plays a significant role in NADPH2 formation and in pentose sugars that are biosynthetic precursors of nucleic acids and amino acids. Cells can be protected from highly reactive oxygen species by NADPH 2 . Deficiency in the hexose monophosphate pathway is linked to numerous disorders. Furthermore, it was also reported that this metabolic pathway could act as a therapeutic target to treat different types of cancers, so treatments at the molecular level could be planned by limiting the synthesis of biomolecules required for proliferating cells provided by the HMP shunt, hence, more experiments still could be carried out to find additional discoveries.

Compared with traditional thermal sterilization process, pulsed magnetic field (PMF) is a non-thermal sterilization technology with superior advantages of maintaining the nutrition and flavor of food. But little is known about its antimicrobial mechanism. To explore its antimicrobial mechanism, the variation of cell membrane, intracellular biological macromolecules and respiratory metabolism of E. coli O157: H7 after PMF treatment, were investigated. The results showed that PMF could cause cell membrane damage and increase cell membrane permeability, reducing the content of three intracellular macromolecules (protein, ATP and DNA), as well as exhibiting inhibition for ATPase activity. The inhibition rate and superposition rate test confirmed the pathway that affecting the respiratory metabolism of E. coli O157:H7 treated with PMF was hexose monophophate pathway (HMP), via reducing the activity of key enzyme glucose-6-phosphate dehydrogenase in HMP. Besides, PMF also exhibited superior antibacterial effect on E. coli O157:H7 when it was applied in vegetable juices.

In this study, a novel inoculation method to mitigate the inhibition of 5-hydroxymethylfurfural (5-HMF) is proposed. Acid algae hydrolysate containing 1.5 g 5-HMF/L and 15 g hexose/L hexose was fed to a continuous fixed bed reactor (C-FBR) partially packed with hybrid-immobilized beads. The inoculation method enabled a high rate of H2 production, due to the reduction of 5-HMF inhibition and enhanced biofilm formation. Maximum hydrogen production was achieved at a hydraulic retention time of 6 h with a hydrogen production rate (HPR) of 20.0 ± 3.3 L H2/L-d and a hydrogen yield (HY) of 2.3 ± 0.4 mol H2/mol hexose added. Butyrate and acetate were the major soluble metabolic products released during fermentation. Quantitative real-time polymerase chain reaction analysis revealed that Clostridium butyricum comprised 94.3% of the total bacteria, which was attributed to the high rate of biohydrogen production.

Dark fermentative biohydrogen production mainly relies on strains that follow the butyric acid fermentation pathway and substrate that could be easily fermented, i.e., hexose. In this paper, biohyd...

Human milk oligosaccharides (HMOs) have attracted much attention in recent years not only as a prebiotic factor, but in particular as an essential component in infant nutrition related to their impact in innate immunity. The backbone structures of complex HMOs generally contain single or repetitive lacto-N-biose (type 1) or lactosamine (type 2) units in either linear or branched chains extending from a lactose core. While all known branched structures originate from 3,6-substitution of the lactosyl core galactose, we here describe a new class of HMOs that tentatively branch at terminal galactose of 6’-galactosyllactose. Another novel feature of this class of HMOs was found in linear oligo-galactosyl chains linked to one of the N-acetylglucosamine (GlcNAc) branches. The novel structures exhibit general formulas with hexose vs. hexosamine contents of 5/2 to 8/2 and can be designated as high-galactose (HG)-HMOs. In addition, up to three fucosyl residues are linked to the octa- to dodecasaccharides, which were detected in two human milk samples from Lewis blood group defined donors. Structural analyses of methylated glycans and their alditols comprised MALDI mass spectrometry, ESI-(CID)MS and linkage analyses by GC-MS of the derived partially methylated alditol acetates. Enzymatic degradation by application of β1-3,4-specific galactosidase supported the presence of terminal galactose linked β1−6 to one of the two GlcNAc branches.

SummaryA common cellular task is to match gene expression dynamically to a range of concentrations of a regulatory molecule. Studying glucose transport in budding yeast, we determine mechanistically how such matching occurs for seven hexose transporters. By combining time-lapse microscopy with mathematical modelling, we find that levels of transporters are history-dependent and are regulated by a push-pull system comprising two types of repressors. Repression by these two types varies with glucose in opposite ways, and not only matches the expression of transporters by their affinity to a range of glucose concentrations, but also the expression of some to how glucose is changing. We argue that matching is favoured by a rate-affinity trade-off and that the regulatory system allows yeast to import glucose rapidly enough to starve competitors. Matching expression to a pattern of input is fundamental, and we believe that push-pull repression is widespread.

Summary • Stomatal opening is caused by guard cell swelling due to an accumulation of osmotica. We investigated the release of carbon from guard cell chloroplasts as a source for the production of organic osmotica. • Photosynthetically active chloroplasts were isolated from guard cell protoplasts of Vicia faba. Export of metabolites into the surrounding medium was analyzed by silicone oil filtering centrifugation and spectrophotometrically by coupled metabolite assays. Effects of external oxaloacetate and 3-phosphoglycerate on photosynthetic electron transport were examined by recording chlorophyll fluorescence. • In the light, guard cell chloroplasts exported triose phosphates, glucose, maltose and hexose phosphates. The presence of phosphate in the medium was essential for the release of phosphorylated compounds and also strongly enhanced the export of glucose and maltose. Total efflux of carbon from illuminated guard cell chloroplasts was on average 486 µatom C (mg Chl)−1 h−1, which was significant with respect to the carbon requirement for stomatal opening. • Metabolites released by illuminated guard cell chloroplasts originated predominantly from starch breakdown. Photosynthetic electron transport provided redox power for the reduction of oxaloacetate and 3-phosphoglycerate.

Wolfberry fruit has been attracting attention for centuries in Asian countries as a traditional herbal medicine and valuable nourishing tonic. Revealing the spatial distribution changes of important endogenous molecules during plant development is of great significance for investigating the physiological roles, nutritional and potential functional values of phytochemicals in wolfberry fruit. However, their spatial distribution information during fruit development has not been extensively explored due to the lack of efficient analytical techniques. In this work, matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) was performed to visualize the spatial distribution of the endogenous molecules during fruit development. From the mass spectrum imaging, the choline, betaine and citric acid were distributed evenly throughout the entire fruit at all development stages. The hexose was distributed in the endocarp and flesh tissue, while sucrose was located in the seeds. Additionally, several phenolic acids and flavonoids were accumulated in the exocarp during fruit development, which indicated that they seemingly played protective roles in wolfberry fruit growth progress against abiotic and biotic stress. From the collected data, we found that the signal intensities of citric acid were decreased, while choline, betaine, hexose and sucrose were increased with fruit development. These results indicate that MALDI-MSI may become a favorable tool for studying of the spatial distribution and effective use of endogenous molecules, which provide a simple and intuitive way for authenticity identification, classification of drug food homologous foods and further understanding the physiological roles of endogenous molecules.

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.

Nucleotide sugars are required for the synthesis of glycoproteins and glycolipids, which play crucial roles in many cellular functions such as cell communication and immune responses. Uridine diphosphate-glucose (UDP-Glc) was previously believed to be the only nucleotide sugar detectable in brain by 31 P-MRS. Using spectra of high SNR and high resolution acquired at 7 T, we showed that multiple nucleotide sugars are coexistent in brain and can be measured simultaneously. In addition to UDP-Glc, these also include UDP-galactose (UDP-Gal), -N-acetyl-glucosamine (UDP-GlcNAc) and -N-acetyl-galactosamine (UDP-GalNAc), collectively denoted as UDP(G). Coexistence of these UDP(G) species is evident from a quartet-like multiplet at -9.8 ppm (M-9.8 ), which is a common feature seen across a wide age range (24-64 years). Lineshape fitting of M-9.8 allows an evaluation of all four UDP(G) components, which further aids in analysis of a mixed signal at -8.2 ppm (M-8.2 ) for deconvolution of NAD+ and NADH. For a group of seven young healthy volunteers, the concentrations of UDP(G) species were 0.04 ± 0.01 mM for UDP-Gal, 0.07 ± 0.03 mM for UDP-Glc, 0.06 ± 0.02 mM for UDP-GalNAc and 0.08 ± 0.03 mM for UDP-GlcNA, in reference to ATP (2.8 mM). The combined concentration of all UDP(G) species (average 0.26 ± 0.06 mM) was similar to the pooled concentration of NAD+ and NADH (average 0.27 ± 0.06 mM, with a NAD+ /NADH ratio of 6.7 ± 2.1), but slightly lower than previously found in an older cohort (0.31 mM). The in vivo NMR analysis of UDP-sugar composition is consistent with those from tissue extracts by other modalities in the literature. Given that glycosylation is dependent on the availability of nucleotide sugars, assaying multiple nucleotide sugars may provide valuable insights into potential aberrant glycosylation, which has been implicated in certain diseases such as cancer and Alzheimer's disease.

Efficient hexose transporters are essential for the development of industrial yeast strains with high fermentation performance. We previously identified a hexose transporter, CgHxt4, with excellent sugar uptake performance at ultra-high glucose concentrations (200 g/L) in the high sugar fermenting yeast C. glycerinogenes. To understand the working mechanism of this transporter, we constructed 87 mutants and examined their glucose uptake performance. The results revealed that five residues (N321, N322, F325, G426, and P427) are essential for the efficient glucose transport of CgHxt4. Subsequently, we focused our analysis on the roles of N321 and P427. Specifically, N321 and P427 are likely to play a role in glucose coordination and conformational flexibility, respectively. Our results help to expand the application potential of this transporter and provide insights into the working mechanism of yeast hexose transporter. • Five residues, transmembrane segments 7 and 10, were found to be essential for CgHxt4. • N321 and P427 are likely to play a role in glucose coordination and conformational flexibility, respectively. • Chimeric CgHxt5.4TM7 significantly enhanced the performance of CgHxt5.

Present knowledge on the quantitative aerobic physiology of the yeastSaccharomyces cerevisiaeduring growth on sucrose as sole carbon and energy source is limited to either adapted cells or to the model laboratory strain CEN.PK113-7D. To broaden our understanding of this matter and open novel opportunities for sucrose-based biotechnological processes, we characterized three strains, with distinct backgrounds, during aerobic batch bioreactor cultivations. Our results reveal that sucrose metabolism inS. cerevisiaeis a strain-specific trait. Each strain displayed a distinct extracellular hexose concentration and invertase activity profiles. Especially, the inferior maximum specific growth rate (0.21 h−1) of the CEN.PK113-7D strain, with respect to that of strains UFMG-CM-Y259 (0.37 h−1) and JP1 (0.32 h−1), could be associated to its low invertase activity (0.04 to 0.09 U mgDM−1). Moreover, comparative experiments with glucose or fructose alone, or in combination, suggest mixed mechanisms of sucrose utilization by the industrial strain JP1, and points out the remarkable ability of the wild isolate UFMG-CM-259 to grow faster on sucrose than on glucose in a well-controlled cultivation system. This work hints to a series of metabolic traits that can be exploited to increase sucrose catabolic rates and bioprocess efficiency.Abstract Figure

Quantitative traits such as human height are measurable phenotypes that show continuous variation over a wide phenotypic range. Enormous effort has recently been put into determining the genetic influences on a variety of quantitative traits, including human genetic diseases, with mixed success. We identified a quantitative trait in a tractable model system, the GAL pathway in yeast, which controls the uptake and metabolism of the sugar galactose. GAL pathway activation depends both on galactose concentration and on the concentrations of competing, preferred sugars such as glucose. Natural yeast isolates show substantial variation in the behavior of the pathway. All studied yeast strains exhibit bimodal responses relative to external galactose concentration, i.e. a set of galactose concentrations existed at which both GAL-induced and GAL-repressed subpopulations were observed. However, these concentrations differed in different strains. We built a mechanistic model of the GAL pathway and identified parameters that are plausible candidates for capturing the phenotypic features of a set of strains including standard lab strains, natural variants, and mutants. In silico perturbation of these parameters identified variation in the intracellular galactose sensor, Gal3p, the negative feedback node within the GAL regulatory network, Gal80p, and the hexose transporters, HXT, as the main sources of the bimodal range variation. We were able to switch the phenotype of individual yeast strains in silico by tuning parameters related to these three elements. Determining the basis for these behavioral differences may give insight into how the GAL pathway processes information, and into the evolution of nutrient metabolism preferences in different strains. More generally, our method of identifying the key parameters that explain phenotypic variation in this system should be generally applicable to other quantitative traits.Author summaryMicrobes adopt elaborate strategies for the preferred uptake and use of nutrients to cope with complex and fluctuating environments. As a result, yeast strains originating from different ecological niches show significant variation in the way they induce genes in the galactose metabolism (GAL) pathway in response to nutrient signals. To identify the mechanistic sources of this variation, we built a mathematical model to simulate the dynamics of the galactose metabolic regulation network, and studied how parameters with different biological implications contributed to the natural variation. We found that variations in the behavior of the galactose sensor Gal3p, the negative feedback node Gal80p, and the hexose transporters HXT were critical elements in the GAL pathway response. Tuning single parameters in silico was sufficient to achieve phenotype switching between different yeast strains. Our computational approach should be generally useful to help pinpoint the genetic and molecular bases of natural variation in other systems.

The aim of this study was to investigate the effect of 20 mg/L 2,4-D on the quality during ripening of on-tree longan fruits. We investigated external and internal properties of the on-tree longan fruits. The results showed that 2,4-D treatment promotes the growth based on the fruit size and weight. The respiration rate, contents of TSS, total soluble sugar, sucrose, glucose, fructose, and hexose revealed an increasing tendency with advancing the maturity and reached the high status during 110-126DPA. By contrast, the relative electric conductivity and TA content displayed a declining trend during the ripening stage, increase with the senescence. All these pieces of information indicated that 2,4-D treatment could effectively promote the sensory quality of on-tree longan fruit, prolong the harvest time to 118DPA, while CK should harvest before 110DPA.

Cofermentation of pentose and hexose is considered the first and most important prerequisite for economically viable conversion of ligno-cellulosic biomass to ethanol. However, lack of robust organisms or fermentation process to convert both hexose and pentose efficiently compromises the overall fermentation performance. To overcome this bottleneck, many strategies and techniques have been attempted, such as exploration and improvement of native cofermenting microbes, engineering of industrial microbes for cofermenting mixed sugars, cocultivation of two or more species, and development of fermentation configurations and strategies. This chapter provides an overview of the current findings and breakthroughs for improved second-generation ethanol production from mixed sugars.

During recent years we have advanced our understanding of plant molecular responses to ultraviolet radiation (UV, 280-400 nm); however, how plants respond to UV radiation under different spectral light qualities is poorly understood. In this study, cucumber plants (Cucumis sativus ‘Lausanna RZ F1’) were grown under monochromatic blue, green, red and broadband white light in combination with UV radiation. The effects of light quality and UV radiation on acclimatory responses were assessed by measuring transcript accumulation of ELONGATED HYPOCOTYL 5 (HY5), CHALCONE SYNTHASE 2 (CHS2) and LIGHT HARVESTING COMPLEX II (LHCII), and the accumulation of flavonoids and hydroxycinnamic acids in the leaves. The growth light backgrounds differentially regulated gene expression and metabolite accumulation. While HY5 and CHS2 transcripts were induced by blue and white light, LHCII was induced by white and red light. Furthermore, UV radiation antagonized the effects of blue, red, green, and white light on transcript accumulation in a gene dependent manner. Plants grown under blue light with supplementary UV radiation increased phenylalanine, flavonol disaccharide I and caffeic acid contents compared to those exposed only to blue light. UV radiation also induced the accumulation of flavonol disaccharide I and II, ferulic acid hexose and coumaric acid hexose in plants grown under green light. Our findings provide further understanding of plant responses to UV radiation in combination with different light spectra and contribute to the design of light recipes for horticultural practices that aim to modify plant metabolism and ultimately improve crop quality., Funding agencies:GUDP (Danish Ministry of Food, Agriculture and Fisheries)Faculty for Business, Science and Technology at Örebro UniversityÖrebro University

The effects of birth weight (BiW; low BiW [LBW] vs. high BiW [HBW]) and estimated breeding value (EBV) for protein deposition (low EBV [LBV] vs. high EBV [HBV]) on N retention, N efficiency, and concentrations of metabolites in plasma and urine related to N efficiency in growing pigs were studied. At an age of 14 wk, 10 LBW–LBV (BiW: 1.07 ± 0.09 [SD] kg; EBV: −2.52 ± 3.97 g/d, compared with an average crossbred pig with a protein deposition of 165 g/d), 10 LBW–HBV (BiW: 1.02 ± 0.13 kg; EBV: 10.47 ± 4.26 g/d), 10 HBW–LBV (BiW: 1.80 ± 0.13 kg; EBV: −2.15 ± 2.28 g/d), and 10 HBW–HBV (BiW: 1.80 ± 0.15 kg; EBV: 11.18 ± 3.68 g/d) male growing pigs were allotted to the experiment. The pigs were individually housed in metabolism cages and were subjected to an N balance study in two sequential periods of 5 d, after an 11-d dietary adaptation period. Pigs were assigned to a protein adequate (A) or protein restricted (R, 70% of A) regime in a change-over design. Pigs were fed 2.8 times the energy requirements for maintenance. Nontargeted metabolomics analyses were performed in urine and blood plasma samples. The N retention (in g/d) was higher in the HBW than in the LBW pigs (P < 0.001). The N retention (in g/[kg metabolic body weight (BW0.75) · d]) and N efficiency, however, were not affected by the BiW of the pigs. The N retention (P = 0.04) and N efficiency (P = 0.04) were higher in HBV than in LVB pigs on the A regime but were not affected by EBV in pigs on the R regime. Restricting the dietary protein supply with 30% decreased the N retention (P < 0.001) but increased the N efficiency (P = 0.003). Nontargeted metabolomics showed that a hexose, free amino acids (AA), and lysophosphatidylcholines were the most important metabolites in plasma for the discrimination between HBV and LBV pigs, whereas metabolites of microbial origin contributed to the discrimination between HBV and LBV pigs in urine. This study shows that BiW does not affect N efficiency in the later life of pigs. Nitrogen efficiency and N retention were higher in HBV than in LBV pigs on the A regime but similar in HBV and LBV pigs on the R regime. In precision feeding concepts aiming to further optimize protein and AA efficiency in pigs, the variation in EBV for protein deposition of pigs should be considered as a factor determining N retention, growth performance, and N efficiency.

Hungateiclostridium thermocellum ATCC 27405 is a promising bacterium for consolidated bioprocessing with a robust ability to degrade lignocellulosic biomass through a multienzyme cellulosomal complex. The bacterium uses the released cellodextrins, glucose polymers of different lengths, as its primary carbon source and energy. In contrast, the bacterium exhibits poor growth on monosaccharides such as fructose and glucose. This phenomenon raises many important questions concerning its glycolytic pathways and sugar transport systems. Until now, the detailed mechanisms of H. thermocellum adaptation to growth on hexose sugars have been relatively poorly explored. In this study, adaptive laboratory evolution was applied to train the bacterium in hexose sugars-based media, and genome resequencing was used to detect the genes that got mutated during adaptation period. RNA-seq data of the first culture growing on either fructose or glucose revealed that several glycolytic genes in the Embden–Mayerhof–Parnas pathway were expressed at lower levels in these cells than in cellobiose-grown cells. After seven consecutive transfer events on fructose and glucose (~42 generations for fructose-adapted cells and ~40 generations for glucose-adapted cells), several genes in the EMP glycolysis of the evolved strains increased the levels of mRNA expression, accompanied by a faster growth, a greater biomass yield, a higher ethanol titer than those in their parent strains. Genomic screening also revealed several mutation events in the genomes of the evolved strains, especially in those responsible for sugar transport and central carbon metabolism. Consequently, these genes could be applied as potential targets for further metabolic engineering to improve this bacterium for bio-industrial usage.

We previously reported the precise structure of acidic free-glycans in human urine. In the present study, structural analysis of neutral free-glycans in urine was performed in fine detail. Urine samples were collected from 21 healthy volunteers and free-glycans extracted from the creatinine-adjusted urine and then fluorescently labeled with 2-aminopyridine. Neutral glycan profiling was achieved by a combination of high-performance liquid chromatography, mass spectrometry, enzymatic digestion, and periodate cleavage. A total of 79 glycans were identified. Because the ABO-blood group antigen containing urinary neutral glycans are major components, profiling patterns were similar between individuals of the same ABO-group. The neutral glycans were composed of lactose-core (Galβ1-4Glc) glycans, type-II N-acetyllactosamine-core (GlcNAcβ1-4Glc) glycans, hexose oligomers, N-glycans and to our surprise β1-3 galactosylglucose-core (Galβ1-3Glc) glycans. Although glycans with a β1-3 galactosylglucose-core were identified as major components in urine, comprising structurally simple isomers of a lactose-core, the core structure has not previously been reported. The major β1-3 galactosylglucose-core glycans were Fucα1-2Galβ1-3(Fucα1-4)Glc, GalNAcα1-3(Fucα1-2)Galβ1-3(Fucα1-4)Glc and Galα1-3(Fucα1-2)Galβ1-3(Fucα1-4)Glc, corresponding to H-, A-, and B-blood group antigens, respectively. Three lactosamine extended β1-3 galactosylglucose-core glycans were also detected as minor components. Elucidating the biosynthesis of β1-3 galactosylglucose will be crucial for understanding the in vivo function of these glycans.