Showing papers on "Sucrose published in 2006"
TL;DR: It is found that rising sugar levels in plants are accompanied by increases in the level of Tre6P, redox activation of AGPase and the stimulation of starch synthesis in vivo, and this results indicate that Tre 6P acts as a signalling metabolite of sugar status in plants.
Abstract: Tre6P (trehalose 6-phosphate) is implicated in sugar-signalling pathways in plants, but its exact functions in vivo are uncertain One of the main obstacles to discovering these functions is the difficulty of measuring the amount of Tre6P in plant tissues We have developed a highly specific assay, using liquid chromatography coupled to MS-Q3 (triple quadrupole MS), to measure Tre6P in the femto-picomole range The Tre6P content of sucrose-starved Arabidopsis thaliana seedlings in axenic culture increased from 18 to 482 pmol·g−1FW (fresh weight) after adding sucrose Leaves from soil-grown plants contained 67 pmol·g−1FW at the end of the night, which rose to 108 pmol·g−1FW after 4 h of illumination Even greater changes in Tre6P content were seen after a 6 h extension of the dark period, and in the starchless mutant, pgm The intracellular concentration of Tre6P in wild-type leaves was estimated to range from 1 to 15 μM It has recently been reported that the addition of Tre6P to isolated chloroplasts leads to redox activation of AGPase (ADPglucose pyrophosphorylase) [Kolbe, Tiessen, Schluepmann, Paul, Ulrich and Geigenberger (2005) Proc Natl Acad Sci USA 102, 11118–11123] Using the new assay for Tre6P, we found that rising sugar levels in plants are accompanied by increases in the level of Tre6P, redox activation of AGPase and the stimulation of starch synthesis in vivo These results indicate that Tre6P acts as a signalling metabolite of sugar status in plants, and support the proposal that Tre6P mediates sucrose-induced changes in the rate of starch synthesis
547 citations
TL;DR: The aim of this review is to explore the broad role of sucrose in the cariogenicity of biofilms, and to present a new insight into its influence on the pathogenesis of dental caries.
Abstract: Dental caries is a biofilm-dependent oral disease, and fermentable dietary carbohydrates are the key environmental factors involved in its initiation and development. However, among the carbohydrates, sucrose is considered the most cariogenic, because, in addition to being fermented by oral bacteria, it is a substrate for the synthesis of extracellular (EPS) and intracellular (IPS) polysaccharides. Therefore, while the low pH environment triggers the shift of the resident plaque microflora to a more cariogenic one, EPS promote changes in the composition of the biofilms’ matrix. Furthermore, it has recently been shown that the biofilm formed in the presence of sucrose presents low concentrations of Ca, Pi, and F, which are critical ions involved in de- and remineralization of enamel and dentin in the oral environment. Thus, the aim of this review is to explore the broad role of sucrose in the cariogenicity of biofilms, and to present a new insight into its influence on the pathogenesis of dental caries.
498 citations
TL;DR: Consuming large amounts of fructose can lead to the development of a complete metabolic syndrome in rodents and in humans, fructose consumed in moderate to high quantities in the diet increases plasma triglycerides and alters hepatic glucose homeostasis, but does not appear to cause muscle insulin resistance or high blood pressure in the short term.
Abstract: Purpose of reviewFructose is consumed in significant amounts in Western diets. An increase in fructose consumption over the past 10–20 years has been linked with a rise in obesity and metabolic disorders. Fructose/sucrose produces deleterious metabolic effects in animal models. This raises concern r
246 citations
TL;DR: The early studies that contributed to the development of a working model of intestinal sugar transport are reviewed, and the recent advances made in understanding the process by which sugars are absorbed in the intestine are detailed.
Abstract: Carbohydrates are an important component of the diet The carbohydrates that we ingest range from simple monosaccharides (glucose, fructose and galactose) to disaccharides (lactose, sucrose) to complex polysaccharides Most carbohydrates are digested by salivary and pancreatic amylases, and are further broken down into monosaccharides by enzymes in the brush border membrane (BBM) of enterocytes For example, lactase-phloridzin hydrolase and sucrase-isomaltase are two disaccharidases involved in the hydrolysis of nutritionally important disaccharides Once monosaccharides are presented to the BBM, mature enterocytes expressing nutrient transporters transport the sugars into the enterocytes This paper reviews the early studies that contributed to the development of a working model of intestinal sugar transport, and details the recent advances made in understanding the process by which sugars are absorbed in the intestine
239 citations
TL;DR: Fructose is found widely in the diet as a free hexose, as the disaccharide, sucrose and in a polymerized form (fructans), which is not hydrolysed or absorbed in the small intestine.
Abstract: Fructose is found widely in the diet as a free hexose, as the disaccharide, sucrose and in a polymerized form (fructans). Free fructose has limited absorption in the small intestine, with up to one half of the population unable to completely absorb a load of 25 g. Average daily intake of fructose varies from 11 to 54 g around the world. Fructans are not hydrolysed or absorbed in the small intestine. The physiological consequences of their malabsorption include increasing osmotic load, providing substrate for rapid bacterial fermentation, changing gastrointestinal motility, promoting mucosal biofilm and altering the profile of bacteria. These effects are additive with other short-chain poorly absorbed carbohydrates such as sorbitol. The clinical significance of these events depends upon the response of the bowel to such changes; they have a higher chance of inducing symptoms in patients with functional gut disorders than asymptomatic subjects. Restricting dietary intake of free fructose and/or fructans may have durable symptomatic benefits in a high proportion of patients with functional gut disorders, but high quality evidence is lacking. It is proposed that confusion over the clinical relevance of fructose malabsorption may be reduced by regarding it not as an abnormality but as a physiological process offering an opportunity to improve functional gastrointestinal symptoms by dietary change.
235 citations
TL;DR: In this paper, the authors collected bulk aerosols from the Howland Experimental Forest in Maine from May to October 2002 and analyzed their TMS derivatives by gas chromatography-mass spectrometry (GC-MS).
212 citations
TL;DR: In this paper, a total of 98 grape cultivars were studied for content and composition of organic acids and sugars in grape juice during two consecutive years, and principal component analysis (PCA) indicated that genotypic correlations among sugar and acid contents were stable and the first three PCs accounted for about 82% of total variance in both years.
Abstract: A total of 98 grape cultivars were studied for content and composition of organic acids and sugars in grape juice during two consecutive years. Glucose and fructose were the predominant sugars in grape berries and ranged from 45.86 to 122.89 mg mL−1, and 47.64 to 131.04 mg mL−1, respectively, in two years. Sucrose was present at trace amounts in most cultivars, but two cultivars of hybrids between Vitis labrusca and V. vinifera contained large amounts of sucrose. Tartaric acid content in berries, varying from 1.57 to 9.09 and 1.54 to 9.05 mg mL−1, respectively, in two years, was significantly higher than malic acid, which ranged from 0.38 to 6.05 and 0.36 to 7.06 mg mL−1, respectively, in two years. Moreover, significantly higher total soluble sugars and fructose and lower total acids and malic acid were found in cultivars from hybrids between V. labrusca and V. vinifera than those in V. vinifera cultivars, and wine grapes had higher total sugars and acids than table grapes from V. vinifera. Principal component analysis (PCA) indicated that genotypic correlations among sugar and acid contents were stable and the first three PCs accounted for about 82% of total variance in both years. PC1 was highly connected with glucose and fructose contents, and sucrose was an important contributor to the variance for PC2, as well as for PC3. PC2 and PC3 were highly connected also with organic acids, but the contributor to variance differed from one year to the next. Tartaric acid was the main contributor to variance in 2003, and malic acid was important in 2004 for PC2 and PC3. In a scatter plot of the score values of all genotypes projected to the PC1 and PC2 plane, three groups of cultivars tend to cluster based on their genetic background or purpose of use. The cultivars of hybrid V. labrusca and V. vinifera were represented by high sugars, especially sucrose, and low acids. Among the cultivars of V. vinifera, wine grapes were found in general to have more sugars and acids than table grapes. The composition of sugars was stable in grape berries between the two years, while acids were sensitive to climate changes. Finally, the different responses of malic and tartaric acids to climate change is discussed. Copyright © 2006 Society of Chemical Industry
193 citations
TL;DR: Binary mutual diffusion coefficients measured by the Taylor dispersion method in two different laboratories (University of Naples, Federico II, Italy, and University of Coimbra, Portugal) are reported for aqueous solutions of lactose, sucrose, glucose, and fructose at various concentrations (0001 to 01) mol·dm-3 and temperatures (29815 to 32815) K as discussed by the authors.
Abstract: Binary mutual diffusion coefficients measured by the Taylor dispersion method in two different laboratories (University of Naples, Federico II, Italy, and University of Coimbra, Portugal) are reported for aqueous solutions of lactose, sucrose, glucose, and fructose at various concentrations (0001 to 01) mol·dm-3 and temperatures (29815 to 32815) K The hydrodynamic radius and activation energy for the diffusion of aqueous sugars are calculated from those results In addition, the measured diffusion coefficients are used with the Hartley equation to estimate activity coefficients for aqueous lactose, sucrose, glucose, and fructose
181 citations
TL;DR: In this paper, the influence of an active seed metabolism on the observed alterations of the sugar concentrations is discussed, and a comparison with the untreated controls revealed that the low levels of both hexoses are the consequence of a decrease in the case of wet processing, whereas they remained unchanged or even increased in dry processing.
Abstract: Quantitative analyses of low molecular sugars in green coffees (Coffea arabica L. var. Acaia) that were processed in parallel either by the traditional wet or the traditional dry method, revealed a close correlation between the kind of post-harvest treatment and the contents of fructose and glucose. While in washed coffee beans (wet processing) only low amounts of these both hexoses were present, those in unwashed coffees (dry processing) were significantly higher. Model-processing experiments in the laboratory confirmed these findings. Moreover, a comparison with the untreated controls revealed that the low levels of both sugars are the consequence of a decrease in the case of wet processing, whereas they remained unchanged or even increased in the case of dry processing. Further minor sugars are also affected by post-harvest treatment. The amounts of galactose, arabinose and mannose show a similar arrangement as those for glucose and fructose, although their overall concentration is about 100-fold lower. Sucrose, the major low molecular sugar in green coffee beans, is not significantly affected by coffee processing. The influence of an active seed metabolism on the observed alterations of the sugar concentrations is discussed.
176 citations
TL;DR: A new procedure to determine individual sugar (sucrose, glucose, and fructose) 13C isotope ratios, using liquid chromatography-isotope ratio mass spectrometry (HPLC-IRMS), has been developed to improve isotopic methods devoted to the study of honey authenticity.
Abstract: A new procedure to determine individual sugar (sucrose, glucose, and fructose) 13C isotope ratios, using liquid chromatography−isotope ratio mass spectrometry (HPLC-IRMS), has been developed to improve isotopic methods devoted to the study of honey authenticity. For this purpose 79 commercial honey samples from various origins were analyzed. Values of δ13Choney ranged from −14.2 to −27.2‰, and δ13Cprotein ranged from −23.6 to −26.9‰. A very strong correlation is observed between the individual sugar 13C ratios, which are altered in the event of sugar addition, even at low levels. The use of Δδ13C [fruct-glu], Δδ13C [fruct-suc], and Δδ13C [gluc-suc] systematic differences as an authenticity criterion permits the sugar addition [C3, beet sugar; or C4, cane sugar, cane syrup, isoglucose syrup, and high-fructose corn syrup (HFCS)] to be reliably detected (DL = 1−10%). The new procedure has advantages over existing methods in terms of analysis time and sensitivity. In addition, it is the first isotopic method ...
170 citations
TL;DR: Northern analyses of genes encoding sucrose synthase and ADP-glucose pyrophosphorylase showed that the expression of both was increased in tubers of the transgenic lines compared with the wild-type, consistent with a role for SnRK1 in regulating carbon flux through the storage pathway to starch biosynthesis.
Abstract: Transgenic potato (Solanum tuberosum cv. Prairie) lines were produced over-expressing a sucrose non-fermenting-1-related protein kinase-1 gene (SnRK1) under the control of a patatin (tuber-specific) promoter. SnRK1 activity in the tubers of three independent transgenic lines was increased by 55%-167% compared with that in the wild-type. Glucose levels were decreased, at 17%-56% of the levels of the wild-type, and the starch content showed an increase of 23%-30%. Sucrose and fructose levels in the tubers of the transgenic plants did not show a significant change. Northern analyses of genes encoding sucrose synthase and ADP-glucose pyrophosphorylase, two key enzymes involved in the biosynthetic pathway from sucrose to starch, showed that the expression of both was increased in tubers of the transgenic lines compared with the wild-type. In contrast, the expression of genes encoding two other enzymes of carbohydrate metabolism, alpha-amylase and sucrose phosphate synthase, showed no change. The activity of sucrose synthase and ADP-glucose pyrophosphorylase was also increased, by approximately 20%-60% and three- to five-fold, respectively, whereas the activity of hexokinase was unchanged. The results are consistent with a role for SnRK1 in regulating carbon flux through the storage pathway to starch biosynthesis. They emphasize the importance of SnRK1 in the regulation of carbohydrate metabolism and resource partitioning, and indicate a specific role for SnRK1 in the control of starch accumulation in potato tubers.
TL;DR: The relative differences between the glass transition temperatures were computed precisely, implying that atomistic molecular dynamics simulations can reproduce trends of T(g) values in amorphous carbohydrates with high quality.
Abstract: Isothermal-isobaric molecular dynamics simulations are used to calculate the specific volume of models of different amorphous carbohydrates (glucose, sucrose, and trehalose) as a function of temperature Plots of specific volume vs temperature exhibit a characteristic change in slope when the amorphous systems change from the glassy to the rubbery state The intersection of the regression lines of data below (glassy state) and above (rubbery state) the change in slope provides the glass transition temperature (T(g)) These predicted glass transition temperatures are compared to experimental T(g) values as obtained from differential scanning calorimetry measurements As expected, the predicted values are systematically higher than the experimental ones (about 12-34 K) as the cooling rates of the modeling methods are about a factor of 10(12) faster Nevertheless, the calculated trend of T(g) values agrees exactly with the experimental trend: T(g)(glucose) < T(g)(sucrose) < T(g)(trehalose) Furthermore, the relative differences between the glass transition temperatures were also computed precisely, implying that atomistic molecular dynamics simulations can reproduce trends of T(g) values in amorphous carbohydrates with high quality
TL;DR: It is suggested that sorbitol distribution plays a key role in fruit carbon metabolism and affects quality attributes such as sugar–acid balance and starch accumulation.
Abstract: Sorbitol and sucrose are major products of photosynthesis distributed in apple trees (Malus domestica Borkh. cv. “Greensleeves”) that affect quality in fruit. Transgenic apple plants were silenced or up-regulated for sorbitol-6-phosphate dehydrogenase by using the CaMV35S promoter to define the role of sorbitol distribution in fruit development. Transgenic plants with suppressed sorbitol-6-phosphate dehydrogenase compensated by accumulating sucrose and starch in leaves, and morning and midday net carbon assimilation rates were significantly lower. The sorbitol to sucrose ratio in leaves was reduced by ≈90% and in phloem exudates by ≈75%. The fruit accumulated more glucose and less fructose, starch, and malic acid, with no overall differences in weight and firmness. Sorbitol dehydrogenase activity was reduced in silenced fruit, but activities of neutral invertase, vacuolar invertase, cell wall-bound invertase, fructose kinase, and hexokinase were unaffected. Analyses of transcript levels and activity of enzymes involved in carbohydrate metabolism throughout fruit development revealed significant differences in pathways related to sorbitol transport and breakdown. Together, these results suggest that sorbitol distribution plays a key role in fruit carbon metabolism and affects quality attributes such as sugar–acid balance and starch accumulation.
TL;DR: Results indicate that sucrose synthase plays an important role in sugar metabolism during sucrose accumulation in the coffee fruit.
Abstract: Sucrose metabolism and the role of sucrose synthase were investigated in the fruit tissues (pericarp, perisperm, and endosperm) of Coffea arabica during development. Acid invertase, sucrose phosphate synthase, and sucrose synthase activities were monitored and compared with the levels of sucrose and reducing sugars. Among these enzymes, sucrose synthase showed the highest activities during the last stage of endosperm and pericarp development and this activity paralleled closely the accumulation of sucrose in these tissues at this stage. Carbon partitioning in fruits was studied by pulse–chase experiments with 14 C-sugars and revealed high rates of sucrose turnover in perisperm and endosperm tissues. Additional feeding experiments with 14 CO2 showed that leaf photosynthesis contributed more to seed development than the pericarp in terms of photosynthate supply to the endosperm. Sugar analysis, feeding experiments, and histological studies indicated that the perisperm plays an important role in this downloading process. It was observed that the perisperm presents a transient accumulation of starch which is degraded as the seed develops. Two full-length cDNAs (CaSUS1 and CaSUS2) and the complete gene sequence of the latter were also isolated. They encode sucrose synthase isoforms that are phylogenetically distinct, indicating their involvement in different physiological functions during cherry development. Contrasting expression patterns were observed for CaSUS1 and CaSUS2 in perisperm, endosperm, and pericarp tissues: CaSUS1 mRNAs accumulated mainly during the early development of perisperm and endosperm, as well as during pericarp growing phases, whereas those of CaSUS2 paralleled sucrose synthase activity in the last weeks of pericarp and endosperm development. Taken together, these results indicate that sucrose synthase plays an important role in sugar metabolism during sucrose accumulation in the coffee fruit.
TL;DR: It is shown that the depression of the gel to liquid-crystalline phase transition temperature (T(m) of the dry membranes below ambient and on the prevention of membrane fusion by sugar glass formation is not lower than those needed to depress fusion to below 20%.
TL;DR: 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.
Abstract: 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.
TL;DR: In this paper, the authors investigated the spectroscopic response in the range 1100-2400 nm of solutions of glucose, fructose, and sucrose at concentrations 5-65% and found that by increasing sugar concentration the water band becomes more symmetric and there is a shift of the absorption maximum toward longer wavelengths.
TL;DR: In this article, a mango (Mangifera indica L., cv. Alphonso) fruit is characterized by a series of biochemical changes resulting in gradual textural softening.
Abstract: Ripening of mango (Mangifera indica L., cv. Alphonso) fruit is characterized by a series of biochemical changes resulting in gradual textural softening. From unripe to ripe stage, the starch content came down from 18% to 0.1%; pectin from 1.9% to 0.5%; cellulose from 2% to 0.9% and hemicelluloses from 0.8% to 0.2%. Concomitantly, the total soluble solids increased from 7% to 20%, total soluble sugars from 1% to 15% and pH increased from 2.8 to 5.1. The increase in activity of several of the carbohydrate-degrading enzymes, which resulted in solubilization of the various polysaccharide fractions, correlated with fruit-softening phenomenon. Efficient distribution of 14C-starch into glucose, fructose and sucrose revealed considerable sugar interconversions indicating active gluconeogenesis during mango fruit ripening. Copyright © 2005 Society of Chemical Industry
TL;DR: In this article, various nitrogen sources were compared with yeast extract for efficient lactic acid production by Lactobacillus delbrueckii (NCIM 2365), and the effect of yeast extract could have been due to its B vitamin content.
TL;DR: The results indicate that the effect of carbohydrate accumulation on photosynthesis is significant in the source leaves, but not in the young sink leaves, and that the decrease in Rubisco content was the main cause of the carbohydrate repression of photosynthesis.
Abstract: Accumulation of non-structural carbohydrate in leaves represses photosynthesis. However, the extent of repression should be different between sink leaves (sugar consumers) and source leaves (sugar exporters). We investigated the effects of carbohydrate accumulation on photosynthesis in the primary leaves of bean (Phaseolus vulgaris L.) during leaf expansion. To increase the carbohydrate content of the leaves, we supplied 20 mM sucrose solution to the roots for 5 d (sugar treatment). Plants supplied only with water and nutrients were used as controls. The carbohydrate contents, which are the sum of glucose, sucrose and starch, of the sugar-treated leaves were 1.5-3 times of those of the control leaves at all developmental stages. In the young sink leaves, the photosynthetic rate at saturating light and at an ambient CO2 concentration (A360) did not differ between the sugar-treated and control leaves. The A360 of sugar-treated source leaves gradually decreased relative to the control source leaves with leaf expansion. The initial slope of the A-Ci (CO2 concentration in the intercellular space) curve, and the Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) content per leaf area showed trends similar to that of A360. Differences in Amax between the treatments were slightly smaller than those in A360. These results indicate that the effect of carbohydrate accumulation on photosynthesis is significant in the source leaves, but not in the young sink leaves, and that the decrease in Rubisco content was the main cause of the carbohydrate repression of photosynthesis.
TL;DR: A novel reagent complements FLIPs for glucose, maltose, ribose, glutamate, and phosphate and will be used for analysis of sucrose-derived carbon flux in bacterial, fungal, plant, and animal cells.
TL;DR: A diurnal variation in leaf heat tolerance due to changes in sugar concentration is demonstrated, but this short-term modification in heat tolerance is super-imposed by long-term changes in heat resistance driven by average temperature of preceding days.
Abstract: In water-stressed leaves, accumulation of neutral osmotica enhances the heat tolerance of photosynthetic electron transport. There are large diurnal and day-to-day changes in leaf sugar content because of variations in net photosynthetic production, respiration and retranslocation. To test the hypothesis that diurnal and day-to-day variations in leaf sugar content and osmotic potential significantly modify the responses to temperature of photosynthetic electron transport rate, we studied chlorophyll fluorescence rise temperatures (i.e. critical temperatures at break-points in fluorescence versus temperature response curves, corresponding to enhanced damage of PSII centers and detachment of pigment-binding complexes) in the dark at a background of weak far-red light (TFR) and under actinic light (TL), and responses of foliar photosynthetic electron transport rate to temperature using gas-exchange and chlorophyll fluorescence techniques in the temperate tree Populus tremula L. Sucrose and sorbitol feeding experiments demonstrated strong increases of fluorescence rise temperatures TFR and TL with decreasing leaf osmotic potential and increasing internal sugar concentration. Similar TFR and TL changes were observed in response to natural variation in leaf sugar concentration throughout the day. Increases in leaf sugar concentration led to an overall down-regulation of the rate of photosynthetic electron transport (J), but increases in the optimum temperature (Topt) of J. For the entire dataset, Topt varied from 33.8 °C to 43 °C due to natural variation in sugars and from 33.8 °C to 52.6 °C in the sugar feeding experiments, underscoring the importance of sugars in modifying the response of J to temperature. However, the correlations between the sugar concentration and fluorescence rise temperature varied between the days. This variation in fluorescence rise temperature was best explained by the average temperature of the preceding 5 or 6 days. In addition, there was a significant year-to-year variation in heat sensitivity of photosynthetic electron transport that was associated with year-to-year differences in endogenous sugar content. Our data demonstrate a diurnal variation in leaf heat tolerance due to changes in sugar concentration, but they also show that this short-term modification in heat tolerance is superimposed by long-term changes in heat resistance driven by average temperature of preceding days.
TL;DR: A functional analysis of the SUT ShSUT1 from sugarcane, an important crop species grown for its ability to accumulate high amounts of sucrose in the stem, is presented and it is found that ShS UT1 is highly selective for sucrose, but has a relatively low affinity.
Abstract: Plant sucrose transporters (SUTs) are members of the glycoside-pentoside-hexuronide (GPH) cation symporter family (TC2.A.2) that is part of the major facilitator superfamily (MFS). All plant SUTs characterized to date function as proton-coupled symporters and catalyze the cellular uptake of sucrose. SUTs are involved in loading sucrose into the phloem and sink tissues, such as seeds, roots and flowers. Because monocots are agriculturally important, SUTs from cereals have been the focus of recent research. Here we present a functional analysis of the SUT ShSUT1 from sugarcane, an important crop species grown for its ability to accumulate high amounts of sucrose in the stem. ShSUT1 was previously shown to be expressed in maturing stems and plays an important role in the accumulation of sucrose in this tissue. Using two-electrode voltage clamping in Xenopus oocytes expressing ShSUT1, we found that ShSUT1 is highly selective for sucrose, but has a relatively low affinity for sucrose (K(0.5) = 8.26 mM at pH 5.6 and a membrane potential of -137 mV). We also found that the sucrose analog sucralose (4,1',6'-trichloro-4,1',6'-trideoxy-galacto-sucrose) is a competitive inhibitor of ShSUT1 with an inhibition coefficient (K(i)) of 16.5 mM. The presented data contribute to our understanding of sucrose transport in plants in general and in monocots in particular.
TL;DR: The higher fruit quality of the wild species compared with L. esculentum may depend more on the continuation of sucrose import during ripening than on osmotic or metabolic particularities such as the hexose/ sucrose-accumulator character or specific enzyme activities.
Abstract: Soluble sugar content has been studied in relation to sucrose metabolism in the hexose-accumulating cultivated tomato Lycopersicon esculentum Mill, the wild relative species Lycopersicon cheesmanii Riley, in the sucrose-accumulating wild relative species Lycopersicon chmielewskii Rick, Kesicky, Fobes & Holle. and in two hexose-accumulating interspecific F1 hybrids (L. esculentum × L. cheesmanii; L. esculentum × L. chmielewskii), cultivated under two irrigation regimes (control: EC = 2.1 and saline: EC = 8.4 dS m–1). Under control conditions the total soluble sugar content (as hexose equivalents) in the ripe fruits of L. cheesmanii was 3-fold higher than in L. esculentum, while L. chmielewskii and both F1 hybrids contained twice as much as the cultivar. With the exception of L. esculentum × L. cheesmanii, salinity increased the sugar content by 1.3 (wild species) and 1.7 times (cultivar and L. esculentum × L. chmielewskii) with respect to control fruits. Wild germplasm or salinity provided two different mechanisms for the increases in fruit sugar content. The hexoses accumulated in ripe fruits were strongly influenced by those accumulated at the start of ripening, but the hydrolysed starch before start of ripening only partially explained the final hexose levels and especially the increase under salinity. The early cell wall acid invertase and the late neutral invertase activities appeared to be related to the amount of hexoses accumulated in ripe fruits. However, no metabolic parameter was positively related to the amount of sugar accumulated (including sucrose). The major differences between genotypes appeared in ripe fruits, in which up to 50% of the total amount of sugars accumulated in the wild species (mainly in L. cheesmanii) and hybrids cannot be explained by the sugars accumulated and the starch hydrolysed before the start of ripening stage. As a consequence, the higher fruit quality of the wild species compared with L. esculentum may depend more on the continuation of sucrose import during ripening than on osmotic or metabolic particularities such as the hexose / sucrose-accumulator character or specific enzyme activities.
TL;DR: Pseudozyma antarctica NRRL Y-7808 was found to produce itaconic acid from glucose and other sugars under nitrogen-limited growth conditions, and glucose and fructose were the most efficiently utilized substrates.
TL;DR: The results indicate that sugar accumulation in tubers during storage in the cold is not a direct consequence of a constraint in carbohydrate oxidation, despite preferential restriction of glycolysis at low temperature.
Abstract: This work investigates the possible causes of cold-induced sweetening in potato by examining the impact of low temperature on carbohydrate metabolism in mature tubers. Metabolism in tuber discs was monitored by determining the redistribution of radiolabel following incubation in [U- 14 C]glucose. Estimates of flux based on the specific activity of hexose phosphates established that while incubation at 48C resulted in an immediate restriction in pathways of carbohydrate oxidation relative to activity at 258C, there was no corresponding increase in flux to soluble sugars. In contrast, prior storage at low temperature stimulated flux to sugars at both 4 and 258C. Comparison of 14 CO2 release from specifically labeled glucose and gluconate fed to tuber discs at 4 and 258C indicated that flux through glycolysis was preferentially restricted relative to the oxidative pentose phosphate pathway at low temperature, irrespective of prior storage temperature. However, the degree of randomization of label between positions C1 and C6 in the fructosyl moiety of sucrose following metabolism of [1- 13 C]glucose established that there was no preferential inhibition of the recycling of triose phosphates to hexose phosphates at low temperature. These results indicate that sugar accumulation in tubers during storage in the cold is not a direct consequence of a constraint in carbohydrate oxidation, despite preferential restriction of glycolysis at low temperature. It is concluded that the cold lability of enzymes catalyzing the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate is not a major factor in cold-induced sweetening in plants and that this widely held hypothesis should be abandoned.
TL;DR: In this paper, the levels of sugar, organic acids, and phenolic acids in stored Yali parsons were investigated using high-performance liquid chromatography and solid-phase microextraction (SPME) methods.
TL;DR: The immobilized biocatalyst was tested in a tubular fixed-bed reactor to investigate its possible application for continuous sucrose hydrolysis in a fixed bed reactor for the preparation of fructose-rich syrup and showed a maximum enzyme activity when immobilized at pH 5.0, but optimum pH activity for both immobilized and free invertases was 5.5.
TL;DR: Comparison of the kinetic composition of these carrot stocks with that of model sugar solutions leads to the proposal that the changes in stock composition result from sugar diffusion, sucrose hydrolysis, and hydroxymethylfurfural (HMF) formation.
Abstract: Solutions obtained by heating carrot roots in water (stocks) are widely used in the food industry, but little information is available regarding the metabolites (intermediates and products of metabolism) found in the stock. The effect of treatment temperature and duration on the sugar composition of stocks was investigated directly by quantitative 1H NMR spectroscopy, to understand the extraction mechanism when processing at 100 °C. Stocks prepared at three different temperatures (50, 75, and 100 °C) were investigated for up to 36 h. Three sugars (sucrose, glucose, and fructose) were detected and quantified. The concentrations of these three sugars reached a maximum after 9 h when the temperature of treatment was 50 or 75 °C. At 100 °C, the sucrose concentration reached a maximum after 3 h, whereas the concentration of glucose and fructose was still increasing at that time. Comparison of the kinetic composition of these carrot stocks with that of model sugar solutions leads to the proposal that the change...
TL;DR: Fungal storage lipid abundances (NLFAs) peaked in summer, during the same period that the highest concentrations of mannitol and trehalose were detected, consistent with these two sugars being stress-induced fungal metabolites, produced due to the low soil moisture observed during this season.