SEARCH · PubMed Health

Results for “SUGARS”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources

PubMed2026

Genomic and functional characterization of sugar transporters reveals potential roles in sugar accumulation in a modern sugarcane cultivar.

Sugarcane (Saccharum spp.) is a globally important sugar crop whose productivity depends on efficient sugar transport from source to sink organs. However, systematic identification and functional characterization of sugar transporters (STs) in sugarcane cultivars remain limited. Here, we identified 190 non-redundant ST genes in sugarcane cultivar Guitang 42 (GT42) and phylogenetically classified them into nine groups within the Monosaccharide Transporter (MST), Sucrose Transporter (SUT), and Sugars Will Eventually be Exported Transporters (SWEET) families. Comparative evolutionary analysis revealed significant lineage-specific expansions in the PMT, STP subfamilies, and SWEET families compared to diploid and wild relatives, likely driven by polyploidization and intensive selection for sugar yield. Transcriptomic profiling across tissues and internode elongation stages demonstrated marked tissue-specific and developmental expression patterns. Yeast complementation assays confirmed the transport activity of candidate MSTs, SUTs and SWEETs, with confocal microscopy verifying their distinct subcellular localization at the plasma membrane, tonoplast, or endoplasmic reticulum. Furthermore, transient overexpression of several candidate transporters (ScSWEET4-T2, ScSWEET15, and ScTST4-T1) in Nicotiana benthamiana modulated soluble sugar accumulation, and their expression in sugarcane protoplasts activated key sugar-responsive marker genes (ScGPT2 and ScWIP4). Together, our study establishes a systematic genomic framework and identifies candidate functional transporters that govern sugar partitioning and storage, providing valuable genetic targets for molecular breeding and quality enhancement in sugarcane.

Functional characterization↗

PubMed1976

The concerted inactivation of Escherichia coli uridine diphosphate galactose 4-epimerase by sugar nucleotide together with a free sugar.

1. The combined effect of the sugar nucleotides UDP-D-fucose or UDP-D-glucuronic acid together with the free sugars D-fucose or L-arabinose is the inactivation of the Escherichia coli enzyme UDP-galactose 4-epimerase (EC 5.1.3.2). The sugar nucleotide or the free sugar alone or the sugar nucleotide plus 5'-Ump do not inactivate the enzyme. 2. The inactivation of the enzyme by its substrate UDP-D-glucose was not affected by the presence of free sugar. 3. In all cases the inactivation observed follows pseudo-first-order kinetics. 4. A comparison of various sugar nucleotides indicates that the hydroxymethyl group at position 6 of the sugar moiety of the natural substrates is important for substrate binding.

Arabinose↗

PubMed1977

Effect of sugars on salt reception in true slime mold Physarum polycephalum. Physicochemical interpretation of interaction between salt and sugar receptions.

Interaction between salt and sugar receptions in plasmodium of Physarum polycephalum was studied by using double-chamber method. Effect of sugars on salt reception was evaluated by measuring membrane potential and the motive force of tactic movement of the slime mold, where salt concentration in one compartment was increased successively with a fixed sugar concentration. Results are summarized as follows: (1) The presence of D-glucose, D-mannose, D-maltose, or sucrose in medium led to increase of the threshold concentration Cth, for salts (chlorides and nitrates of Li, Na, K), whereas D-ribose decreased the threshold for salt reception. D-galactose showed no appreciable effect on Cth of every salt species examined. No change in Cth for salt reception was observed until concentration of sugars exceeded their respective thresholds. (2) Double logarithmic plots of Cth for salts against sugar concentration followed different straight lines for different cations, whose slopes being closely correlated with the effects of lyotropic number of anions in the absence of sugars. (3) Plots of log Cth against the reciprocal of the absolute temperature, 1/T, gave linear relations, and the slopes of the straight line became small with increase of sugar concentration above their respective thresholds. Experimental results obtained here suggest that the structure of water at the interface of cell membrane plays an indispensable role in the interaction between salt and sugar receptions.

Anions↗

PubMed1987

Mechanism of sugar transport through the sugar-specific LamB channel of Escherichia coli outer membrane.

Lipid bilayer experiments were performed with the sugar-specific LamB (maltoporin) channel of Escherichia coli outer membrane. Single-channel analysis of the conductance steps caused by LamB showed that there was a linear relationship between the salt concentration in the aqueous phase and the channel conductance, indicating only small or no binding between the ions and the channel interior. The total or the partial blockage of the ion movement through the LamB channel was not dependent on the ion concentration in the aqueous phase. Both results allowed the investigation of the sugar binding in more detail, and the stability constants of the binding of a large variety of sugars to the binding site inside the channel were calculated from titration experiments of the membrane conductance with the sugars. The channel was highly cation selective, both in the presence and absence of sugars, which may be explained by the existence of carbonyl groups inside the channel. These carbonyl groups may also be involved in the sugar binding via hydrogen bonds. The kinetics of the sugar transport through the LamB channel were estimated relative to maltose by assuming a simple one-site, two-barrier model from the relative rates of permeation taken from M. Luckey and H. Nikaido (Proc. Natl. Acad. Sci. USA 77:165-171 (1980a)) and the stability constants for the sugar binding given in this study.

Bacterial Outer Membrane Proteins↗

PubMed2006

Identification of sugar-modulated genes and evidence for in vivo sugar sensing in Arabidopsis.

Sugar status regulates mechanisms controlling growth and development of plants. We studied the effects of sucrose at a genome-wide level in dark-grown 4-day-old Arabidopsis thaliana seedlings, identifying 797 genes strongly responsive to sucrose. Starting from the microarray analysis data, four up-regulated (At5g41670, At1g20950, At1g61800, and At2g28900) and four down-regulated (DIN6, At4g37220, At1g28330, and At1g74670) genes were chosen for further characterisation and as sugar sensing markers for in vivo analysis. The sugar modulation pattern of all eight genes was confirmed by real time RT-PCR analysis, revealing different concentration thresholds for sugar modulation. Finally, sugar-regulation of gene expression was demonstrated in vivo by using the starchless pgm mutant, which is unable to produce transitory starch. Sucrose-inducible genes are upregulated in pgm leaves at the end of a light treatment, when soluble sugars levels are higher than in the wild type. Conversely, sucrose-repressible genes show a higher expression at the end of the dark period in the mutant, when the levels of sugars in the leaf are lower. The results obtained indicate that the transcriptional response to exogenous sucrose allows the identification of genes displaying a pattern of expression in leaves compatible with their sugar-modulation in vivo.

Arabidopsis↗

PubMed1989

Development of a buffer system for dialysis of bovine spermatozoa before freezing. II. Effect of sugars and sugar alcohols on posthaw motility.

Two experiments were conducted to evaluate the effect of different levels of sugars (glucose, lactose and raffinose) and the effect of those sugars (C(3) to C(6)) or their correspondent sugar alcohols on the dialysis of bovine semen. First, the effect of isosmotic solutions of glucose, lactose or raffinose at five different levels (0, 25, 50, 75, 95% V/V) on sperm motility of semen dialyzed prior to freezing were studied. These levels were used in extenders and dialysates, and the final volume was complemented with Piperazine-N-N-BIS (2-ethane sulfonic acid (PIPES) titrated to pH 7.0 with TRIS (hydroxymethyl) amino-methane (TRIS) to form PIPEST or a 1:1 (V/V) combination between PIPEST and sodium citrate solutions. In the second experiment, 30% of the buffer volume contained solutions of sugars (C(3) or C(6)) or their correspondent sugar alcohol, and the final volume was completed with PIPEST-citrate buffer. Semen aliquots were extended (1:10) and dialyzed (1:50) for 2 h while cooling from 37 to 5 degrees C in semipermeable dialysis bags of 12,000 to 14,000 molecular weight cut off. The samples were frozen in pellets 1 h after dialysis was terminated. Sperm survival was significantly higher in PIPEST-citrate than in PIPEST buffer alone (P<0.05). No significant difference (P>0.05) was obtained between the use of glucose or lactose or between lactose and raffinose. High levels of sugar appeared to be detrimental to sperm motility of fresh and thawed semen samples. Motility of cells extended in buffers containing 30% (V/V) isosmotic solutions of glucose, galactose, ribose, xylose, arabinose or their correspondent sugar alcohols was significantly higher (P<0.05) than their motility in extenders without sugar.

Journal Article↗

PubMed1988

Sugar-activated ion transport in canine lingual epithelium. Implications for sugar taste transduction.

There is good evidence indicating that ion-transport pathways in the apical regions of lingual epithelial cells, including taste bud cells, may play a role in salt taste reception. In this article, we present evidence that, in the case of the dog, there also exists a sugar-activated ion-transport pathway that is linked to sugar taste transduction. Evidence was drawn from two parallel lines of experiments: (a) ion-transport studies on the isolated canine lingual epithelium, and (b) recordings from the canine chorda tympani. The results in vitro showed that both mono- and disaccharides in the mucosal bath stimulate a dose-dependent increase in the short-circuit current over the concentration range coincident with mammalian sugar taste responses. Transepithelial current evoked by glucose, fructose, or sucrose in either 30 mM NaCl or in Krebs-Henseleit buffer (K-H) was partially blocked by amiloride. Among current carriers activated by saccharides, the current response was greater with Na than with K. Ion flux measurements in K-H during stimulation with 3-O-methylglucose showed that the sugar-evoked current was due to an increase in the Na influx. Ouabain or amiloride reduced the sugar-evoked Na influx without effect on sugar transport as measured with tritiated 3-O-methylglucose. Amiloride inhibited the canine chorda tympani response to 0.5 M NaCl by 70-80% and the response to 0.5 M KCl by approximately 40%. This agreed with the percent inhibition by amiloride of the short-circuit current supported in vitro by NaCl and KCl. Amiloride also partially inhibited the chorda tympani responses to sucrose and to fructose. The results indicate that in the dog: (a) the ion transporter subserving Na taste also subserves part of the response to K, and (b) a sugar-activated, Na-preferring ion-transport system is one mechanism mediating sugar taste transduction. Results in the literature indicate a similar sweet taste mechanism for humans.

Amiloride↗

PubMed1995

Repeatability of the sugar-absorption test, using lactulose and mannitol, for measuring intestinal permeability for sugars.

Differential sugar-absorption tests for measuring intestinal permeability for sugars have been studied in a variety of gastrointestinal diseases. Their use in general practice has been hampered by a lack of data on reference values and repeatability of the test and the laboratory assay. In this study, we determined the reference values of the sugar-absorption test, using lactulose and mannitol as probe molecules, for children and adults. The repeatability of the test is good; linear relationship: slope, 0.825 [95% confidence interval (CI), 0.571, 1.152); intercept, 0.005 (95% CI, -0.004, 0.010). The repeatability of the laboratory assay for the sugar-absorption test is excellent; linear relationship: slope, 1.014 (95% CI, 0.870, 1.094); intercept, 0.002 (95% CI, -0.005, 0.010). The validation of the sugar-absorption test makes the test useful as a simple, noninvasive, reliable intestinal permeability test for sugars, which can be of use for clinical practice. Taking possible interfering factors into account, the sugar-absorption test can be used as a diagnostic test for enteropathy of different etiologies and evaluation of therapeutic interventions in both children and adults. Studies with the sugar-absorption test may clarify the role of intestinal permeability in the pathophysiology of a variety of gastrointestinal diseases.

Adolescent↗

PubMed1996

Molecular cloning, immunochemical localization to the vacuole, and expression in transgenic yeast and tobacco of a putative sugar transporter from sugar beet.

Several plant genes have been cloned that encode members of the sugar transporter subgroup of the major facilitator superfamily of transporters. Here we report the cloning, expression, and membrane localization of one of these porters found in sugar beet (Beta vulgaris L.). This clone, cDNA-1, codes for a protein with 490 amino acids and an estimated molecular mass of 54 kD. The predicted membrane topology and sequence homology suggest that cDNA-1 is a member of the sugar transporter family. RNA gel blot analysis revealed that this putative sugar transporter is expressed in all vegetative tissues and expression increases with development in leaves. DNA gel blot analysis indicated that multiple gene copies exist for this putative sugar transporter in the sugar beet genome. Antibodies directed against small peptides representing the N- and C-terminal domains of the cDNA1 protein identified a 40-kD polypeptide in microsomes isolated from cDNA-1-transformed yeast (Saccharomyces cerevisiae). Moreover, the same protein was identified in sugar beet and transgenic tobacco (Nicotaina tobacum L.) membrane fractions. Detailed analysis of the transporter's distribution across linear sucrose gradients and flotation centrifugations showed that it co-migrates with tonoplast membrane markers. We conclude that this carrier is located on the tonoplast membrane and that it may mediate sugar partitioning between the vacuole and cytoplasmic compartments.

Amino Acid Sequence↗

PubMed2000

Sugar uptake and transport in rice embryo. Expression of companion cell-specific sucrose transporter (OsSUT1) induced by sugar and light.

We investigated sugar uptake and transport in rice (Oryza sativa) embryo during grain germination. Endogenous sugar levels, accumulation of starch granules, and gene expression of a rice sucrose transporter (OsSUT1) were examined using rice embryos germinated with or without exogenous sugar supply. Starch granules remarkably accumulated in the cells around vascular bundles as a consequence of the sugar taken up by the embryos, indicating that the taken-up sugars are transiently converted into starch. In situ detection for OsSUT1 mRNA indicated its localization in the phloem companion cells. Furthermore, northern-blot and in situ hybridization analyses showed that OsSUT1 expression is not detectable in embryos subjected to sugar starvation conditions, whereas its expression is enhanced by an increased endogenous sugar level. Overall results indicate that the expression of companion cell-specific sucrose transporter, OsSUT1 is regulated by the endogenous sugar status as well as light exposure.

Biological Transport↗

PubMed2005

Studies on growth and metabolism of Oenococcus oeni on sugars and sugar mixtures.

AIMS: To study the effect of sugars and sugar mixtures on the growth kinetics of Oenococcus oeni NCIMB 11648 in batch culture with the aim of producing a high cell productivity system for starter cultures. METHODS AND RESULTS: The growth of O. oeni was investigated on single sugars (glucose, fructose or sucrose) and their mixtures (glucose-fructose, glucose-sucrose or fructose-sucrose). Better growth was obtained on sugar mixtures compared with growth on a single sugar. The production system of O. oeni biomass was investigated in batch culture with or without pH control with respect to kinetics, specific growth rate and biomass yield. The effect of pH and substrate concentration on fermentation balances and ATP yield were determined. The optimal growth of O. oeni was achieved on the glucose-fructose mixture (9 g l(-1), 1 : 1) at pH 4.5 and 25 degrees C with pH control, with highest cell volumetric productivity (7.9 mg cell l(-1) h(-1)), biomass yield (0.041 g cell g(-1) sugar) and specific growth rate (0.066 h(-1)). CONCLUSIONS: The limitations to the growth of O. oeni were pH and inhibition by end product resulting in poor utilization of the medium with low cell yields. The cell productivity of the system can be improved by the appropriate use of mixed sugar growth medium. SIGNIFICANCE AND IMPACT OF THE STUDY: This study uniquely showed that appropriate sugar mixtures with the correct environmental conditions can significantly improve the productivity of O. oeni cultures.

Acetates↗

PubMed2004

Adjustment of diurnal starch turnover to short days: depletion of sugar during the night leads to a temporary inhibition of carbohydrate utilization, accumulation of sugars and post-translational activation of ADP-glucose pyrophosphorylase in the following light period.

A larger proportion of the fixed carbon is retained as starch in the leaf in short days, providing a larger store to support metabolism and carbon export during the long night. The mechanisms that facilitate this adjustment of the sink-source balance are unknown. Starchless pgm mutants were analysed to discover responses that are triggered when diurnal starch turnover is disturbed. Sugars accumulated to high levels during the day, and fell to very low levels by the middle of the night. Sugars rose rapidly in the roots and rosette after illumination, and decreased later in the light period. Global transcript profiling revealed only small differences between pgm and Col0 at the end of the day but large differences at the end of the night, when pgm resembled Col0 after a 4-6 h prolongation of the night and many genes required for biosynthesis and growth were repressed [Plant J. 37 (2004) 914]. It is concluded that transient sugar depletion at the end of the night inhibits carbon utilization at the start of the ensuing light period. A second set of experiments investigated the stimulation of starch synthesis in response to short days in wild-type Col0. In short days, sugars were very low in the roots and rosette at the end of the dark period, and after illumination accumulated rapidly in both organs to levels that were higher than in long days. The response resembles pgm, except that carbohydrate accumulated in the leaf as starch instead of sugars. A similar response was found after transfer from long to short days. Inclusion of sugar in the rooting medium attenuated the stimulation of starch synthesis. Post-translational activation of ADP-glucose pyrophosphorylase (AGPase) was increased in pgm, and in Col0 in short days. It is concluded that starch synthesis is stimulated in short day conditions because sugar depletion at the end of the night triggers a temporary inhibition of growth and carbohydrate utilization in the first part of the light period, leading to transient accumulation of sugar and activation of AGPase.

Arabidopsis↗

PubMed2003

Simple-sugar meals target GLUT2 at enterocyte apical membranes to improve sugar absorption: a study in GLUT2-null mice.

The physiological significance of the presence of GLUT2 at the food-facing pole of intestinal cells is addressed by a study of fructose absorption in GLUT2-null and control mice submitted to different sugar diets. Confocal microscopy localization, protein and mRNA abundance, as well as tissue and membrane vesicle uptakes of fructose were assayed. GLUT2 was located in the basolateral membrane of mice fed a meal devoid of sugar or containing complex carbohydrates. In addition, the ingestion of a simple sugar meal promoted the massive recruitment of GLUT2 to the food-facing membrane. Fructose uptake in brush-border membrane vesicles from GLUT2-null mice was half that of wild-type mice and was similar to the cytochalasin B-insensitive component, i.e. GLUT5-mediated uptake. A 5 day consumption of sugar-rich diets increased fructose uptake fivefold in wild-type tissue rings when it only doubled in GLUT2-null tissue. GLUT5 was estimated to contribute to 100 % of total uptake in wild-type mice fed low-sugar diets, falling to 60 and 40 % with glucose and fructose diets respectively; the complement was ensured by GLUT2 activity. The results indicate that basal sugar uptake is mediated by the resident food-facing SGLT1 and GLUT5 transporters, whose mRNA abundances double in long-term dietary adaptation. We also observe that a large improvement of intestinal absorption is promoted by the transient recruitment of food-facing GLUT2, induced by the ingestion of a simple-sugar meal. Thus, GLUT2 and GLUT5 could exert complementary roles in adapting the absorption capacity of the intestine to occasional or repeated loads of dietary sugars.

Animals↗

PubMed2003

Fragmentation studies of noncovalent sugar-sugar complexes by infrared atmospheric pressure MALDI.

An investigation of sugar-sugar noncovalent complex fragmentation was conducted using a 2.94 microm Er:YAG laser for infrared (IR) atmospheric pressure matrix-assisted laser desorption/ionization (AP MALDI) on an ion trap mass spectrometer (ITMS). This approach allowed the analysis of weak noncovalent complexes between a variety of biologically relevant oligosaccharides. The strength of interaction varied with different sugar structures, potentially due to varying strength of hydrogen bonding networks. In some cases, fragmentation of intramolecular sugar bonds preceded breakdown of the noncovalent complex. This result appeared primarily when complexes contained sugars with at least one sialic acid. Globotrios dimers also showed intramolecular fragmentation in preference to breakdown of the noncovalent dimer. This technique will allow further study of sugar-sugar interactions known to play a role in cellular interactions.

Atmospheric Pressure↗

PubMed2000

Synthesis and conformational studies of peptidomimetics containing furanoid sugar amino acids and a sugar diacid.

Furanoid sugar amino acids (1) were synthesized and used as dipeptide isosteres to induce interesting turn structures in small linear peptides. They belong to a new variety of designed hybrid structures that carry both amino and carboxyl groups on rigid furanose sugar rings. Four such molecules, 6-amino-2,5-anhydro-6-deoxy-D-gluconic acid (3, Gaa) and its mannonic (4, Maa), idonic (5, Iaa), and a 3,4-dideoxyidonic (6, ddIaa) congeners were synthesized. The synthesis followed a novel reaction path in which an intramolecular 5-exo S(N)2 opening of the hexose-derived terminal aziridine ring in 2 by the gamma-benzyloxy oxygen with concomitant debenzylation occurred during pyridinium dichromate oxidation of the primary delta-hydroxyl group to carboxyl function, leading to the formation of furanoid sugar amino acid frameworks in a single step. Incorporation of these furanoid sugar amino acids into Leu-enkephalin replacing its Gly-Gly portion gave analogues 8-11. Detailed structural analysis of these molecules by circular dichroism (CD) and various NMR techniques in combination with constrained molecular dynamics (MD) simulations revealed that two of these analogues, 8a and 10a, have folded conformations composed of an unusual nine-membered pseudo beta-turn-like structure with a strong intramolecular H-bond between LeuNH --> sugarC3-OH. This, in turn, brings the two aromatic rings of Tyr and Phe in close proximity, a prerequisite for biological activities of opioid peptides. The analgesic activities of 8a,b determined by mouse hot-plate and tail-clip methods were similar to that of Leu-enkephalin methyl ester. The syn disposition of the beta-hydroxycarboxyl motif on the sugar rings appears to be the driving force to nucleate the observed turn structures in some of these molecules (8 and 10). Repetition of the motif on both sides of a furanose ring resulted in a novel molecular design of sugar diacid, 2,5-anhydro-D-idaric acid (7, Idac). Bidirectional elongation of the diacid moieties of 7 with identical peptide strands led to the formation of a C2-symmetric reverse-turn mimetic 12 which displayed a very ordered structure consisting of identical intramolecular H-bonds at two ends between LeuNH --> sugar-OH, the same as in 8 and 10.

Amino Acids↗

PubMed1970

Structural requirements for active intestinal transport. The nature of the carrier-sugar bonding at C-2 and the ring oxygen of the sugar.

Several weakly transported sugars were tested for transport by the Na(+)-dependent sugar carrier with slices of everted hamster intestinal tissue. Sugars were assumed to be transported by this carrier if the accumulation was diminished in the absence of Na(+) and in the presence of the competitive inhibitor 1,5-anhydro-d-glucitol. The extent of accumulation was correlated with the number of hydroxyl groups in the d-gluco configuration if the ring oxygen was placed in the normal d-glucose position. 5-Thio-d-glucose, with a sulphur atom in the ring, was transported at about the same rate as d-glucose and had a similar K(i) for d-galactose transport, but myoinositol was poorly accumulated. It is suggested that there is no hydrogen bonding at the ring oxygen atom, but that the oxygen atom is found at this position as a result of steric constraints. No sugar without a hydroxyl group in the d-gluco position at C-2 of the sugar, including d-mannose, 2-deoxy-d-glucose, 2-chloro-2-deoxy-d-glucose and 2-deoxy-2-fluoro-d-glucose, was transported by the Na(+)-dependent carrier, but these sugars and l-fucose weakly and competitively inhibit the Na(+)-dependent accumulation of l-glucose into slices of everted hamster intestinal tissue. It is concluded that the bond between the carrier and C-2 of the sugar may be covalent, and a possible mechanism for active intestinal transport is proposed.

Animals↗

PubMed1987

The effect of trypsin on sugar uptake in rat thymocytes. Modulation of cellular cyclic AMP concentration and the sugar-transport system.

I have shown that cyclic AMP stimulates sugar uptake in rat thymocytes. However, trypsin treatment, which increases rat thymocyte cyclic AMP concentration, fails to increase sugar uptake. The purpose of the present study is to examine this seeming inconsistency, and to evaluate further the function of trypsin. Mild trypsin treatment of rat thymocytes produced a dose-related increase in cellular cyclic AMP concentration. Trypsin produced the same proportionate increase in cyclic AMP concentration in the presence or absence of optimal concentrations of the phosphodiesterase inhibitor 3-isobutyl-l-methylxanthine, which suggests that trypsin acts to increase thymocyte cyclic AMP concentration by stimulating adenylate cyclase activity. Trypsin at concentrations of 0.3 mg/ml and less had no effect on the uptake of the glucose analogue 2-deoxy-D-glucose (2-DG), whereas at concentrations of 1 mg/ml and higher trypsin produced a small, dose-related, decrease in basal 2-DG uptake, becoming significantly lower than control values only at 5 mg/ml (-22.7%, P less than 0.05). Thymocyte sugar transporters, characterized by means of cytochalasin B binding, consist of a single class of sites with an apparent KD of 0.15 microM and maximum binding capacity of 2.73 pmol/20 x 10(6) cells (8.4 x 10(4) sites/thymocyte). Trypsin produced a dose-related decrease in the sugar-displaceable binding of cytochalasin B, so that at 5 mg of trypsin/ml the number of sugar transporters was decreased by approx. 50%. Thus trypsin treatment of rat thymocytes on the one hand increases cellular cyclic AMP concentration, which itself potentiates 2-DG uptake, and on the other hand decreases the number of sugar transporters, which itself decreases cellular sugar uptake, indicating that the apparent effect of trypsin on thymocyte 2-DG uptake is the result of the balance of its effects on these two systems.

Animals↗

PubMed2003

A novel WRKY transcription factor, SUSIBA2, participates in sugar signaling in barley by binding to the sugar-responsive elements of the iso1 promoter.

SURE (sugar responsive) is a cis element in plant sugar signaling. The SURE element was reported first for potato, in which it confers sugar responsiveness to the patatin promoter. A SURE binding transcription factor has not been isolated. We have isolated a transcription factor cDNA from barley and purified the corresponding protein. The transcription factor, SUSIBA2 (sugar signaling in barley), belongs to the WRKY proteins and was shown to bind to SURE and W-box elements but not to the SP8a element in the iso1 promoter. Nuclear localization of SUSIBA2 was demonstrated in a transient assay system with a SUSIBA2:green fluorescent protein fusion protein. Exploiting the novel transcription factor oligodeoxynucleotide decoy strategy with transformed barley endosperm provided experimental evidence for the importance of the SURE elements in iso1 transcription. Antibodies against SUSIBA2 were produced, and the expression pattern for susiba2 was determined at the RNA and protein levels. It was found that susiba2 is expressed in endosperm but not in leaves. Transcription of susiba2 is sugar inducible, and ectopic susiba2 expression was obtained in sugar-treated leaves. Likewise, binding to SURE elements was observed for nuclear extracts from sugar-treated but not from control barley leaves. The temporal expression of susiba2 in barley endosperm followed that of iso1 and endogenous sucrose levels, with a peak at approximately 12 days after pollination. Our data indicate that SUSIBA2 binds to the SURE elements in the barley iso1 promoter as an activator. Furthermore, they show that SUSIBA2 is a regulatory transcription factor in starch synthesis and demonstrate the involvement of a WRKY protein in carbohydrate anabolism. Orthologs to SUSIBA2 were isolated from rice and wheat endosperm.

Amino Acid Sequence↗