Showing papers on "Sucrose published in 2008"
TL;DR: The hypothesis that high fructose consumption may not only lead to liver damage through overfeeding but also may be directly pro-inflammatory by increasing intestinal translocation of endotoxin is supported.
470 citations
Journal Article•
TL;DR: Over 10% of Americans' daily calories were from fructose, suggesting that fructose consumption has increased, and further research is needed to understand the impact of increased intake of fructose on human health.
Abstract: Context
High fructose intake has been associated with increased de novo lipogenesis in the liver as well as increased plasma triglycerides, insulin resistance, and obesity. Fructose occurs naturally in fruits and vegetables; however, it is added to many processed foods as table sugar (sucrose) and high-fructose corn syrup. Dietary data from a nationally representative sample in 1977–1978 estimated that mean consumption of fructose was 37 g/day (8% of total intake). Little is known about more recent fructose consumption patterns.
416 citations
TL;DR: The meta-analysis shows that fructose intakes from 0 to >or=90 g/d have a beneficial effect on HbA(1c), and significant effects on postprandial triacylglycerols are not evident unless >50 g fructose/d is consumed, and no significant effects are seen for fasting triacy lglycerol or body weight with intakes of
234 citations
TL;DR: Sucrose and HFCS do not have substantially different short-term endocrine/metabolic effects, and in male subjects, short- term consumption of sucrose andHFCS resulted in postprandial TG responses comparable to those induced by fructose.
230 citations
TL;DR: It is shown that consumption of fructose-sweetened beverages substantially increases postprandial triacylglycerol concentrations compared with glucose- sweetened beverages, and apolipoprotein B concentrations were also increased in subjects consuming fructose, but not in those consuming glucose.
220 citations
TL;DR: A mechanism of HMF formation from sucrose is proposed, according to which sucrose degrades into glucose and a very reactive fructofuranosyl cation in dry systems this cation can be effectively converted directly into HMF.
Abstract: Although it is generally assumed that the reactivity of sucrose, a nonreducing sugar, in the Maillard reaction is due to its hydrolysis into free glucose and fructose, however, no direct evidence has been provided for this pathway, especially in dry and high temperature systems. Using specifically 13C-labeled sucrose at C-1 of the fructose moiety, HMF formation was studied at different temperatures. Under dry pyrolytic conditions and at temperatures above 250 °C, 90% of HMF originated from fructose moiety and only 10% originated from glucose. Alternatively, when sucrose was refluxed in acidic methanol at 65 °C, 100% of HMF was generated from the glucose moiety. Moreover, the relative efficiency of the known HMF precursor 3-deoxyglucosone to generate HMF was compared to that of glucose, fructose and sucrose. Glucose exhibited a much lower conversion rate than 3-deoxyglucosone, however, both fructose and sucrose showed much higher conversion rates than 3-deoxyglucosone thus precluding it as a major precurso...
188 citations
TL;DR: The citrus-processing industry generates in the Mediterranean area huge amounts of orange peel as a byproduct from the industrial extraction of citrus juices to reduce its environmental impact as well as to provide an extra profit, this residue was investigated in this study as an alternative substrate for the fermentative production of citric acid.
Abstract: The citrus-processing industry generates in the Mediterranean area huge amounts of orange peel as a byproduct from the industrial extraction of citrus juices. To reduce its environmental impact as well as to provide an extra profit, this residue was investigated in this study as an alternative substrate for the fermentative production of citric acid. Orange peel contained 16.9% soluble sugars, 9.21% cellulose, 10.5% hemicellulose, and 42.5% pectin as the most important components. To get solutions rich in soluble and starchy sugars to be used as a carbon source for citric acid fermentation, this raw material was submitted to autohydrolysis, a process that does not make use of any acidic catalyst. Liquors obtained by this process under optimum conditions (temperature of 130 °C and a liquid/solid ratio of 8.0 g/g) contained 38.2 g/L free sugars (8.3 g/L sucrose, 13.7 g/L glucose, and 16.2 g/L fructose) and significant amounts of metals, particularly Mg, Ca, Zn, and K. Without additional nutrients, these liq...
185 citations
TL;DR: Differential carbon partitioning in the wheat stem is one mechanism that contributes to genotypic variation in WSC accumulation, and down-regulation of Suc synthase and soluble acid invertase in high WSC lines was accompanied by significant decreases in the mRNA levels of enzyme families related to sugar catabolic pathways.
Abstract: Water-soluble carbohydrates (WSCs; composed of mainly fructans, sucrose [Suc], glucose [Glc], and fructose) deposited in wheat (Triticum aestivum) stems are important carbon sources for grain filling. Variation in stem WSC concentrations among wheat genotypes is one of the genetic factors influencing grain weight and yield under water-limited environments. Here, we describe the molecular dissection of carbohydrate metabolism in stems, at the WSC accumulation phase, of recombinant inbred Seri/Babax lines of wheat differing in stem WSC concentrations. Affymetrix GeneChip analysis of carbohydrate metabolic enzymes revealed that the mRNA levels of two fructan synthetic enzyme families (Suc:Suc 1-fructosyltransferase and Suc:fructan 6-fructosyltransferase) in the stem were positively correlated with stem WSC and fructan concentrations, whereas the mRNA levels of enzyme families involved in Suc hydrolysis (Suc synthase and soluble acid invertase) were inversely correlated with WSC concentrations. Differential regulation of the mRNA levels of these Suc hydrolytic enzymes in Seri/Babax lines resulted in genotypic differences in these enzyme activities. Down-regulation of Suc synthase and soluble acid invertase in high WSC lines was accompanied by significant decreases in the mRNA levels of enzyme families related to sugar catabolic pathways (fructokinase and mitochondrion pyruvate dehydrogenase complex) and enzyme families involved in diverting UDP-Glc to cell wall synthesis (UDP-Glc 6-dehydrogenase, UDP-glucuronate decarboxylase, and cellulose synthase), resulting in a reduction in cell wall polysaccharide contents (mainly hemicellulose) in the stem of high WSC lines. These data suggest that differential carbon partitioning in the wheat stem is one mechanism that contributes to genotypic variation in WSC accumulation.
174 citations
TL;DR: The present study suggests that C. zofingiensis is suitable for the production of natural astaxanthin on a massive scale by using glucose fed-batch fermentation and high cell dry weight concentration, which are much higher than those ever reported in the alga.
171 citations
TL;DR: The power densities generated from the mini-MFC exposed to oxygen led to significant changes in current production over time with repeated feedings of these carbon nutrients, demonstrating the importance of studying microbial anolytes under diverse environmental conditions.
168 citations
TL;DR: It is shown that suc1 mutant pollen is defective in vivo, as evidenced by segregation distortion, and also has low rates of germination in vitro, and microarray analysis revealed reduced expression of many genes important for anthocyanin biosynthesis.
Abstract: The Arabidopsis (Arabidopsis thaliana) sucrose transporter AtSUC1 (At1g71880) is highly expressed in pollen; however, its function has remained unknown. Here, we show that suc1 mutant pollen is defective in vivo, as evidenced by segregation distortion, and also has low rates of germination in vitro. AtSUC1-green fluorescent protein was localized to the plasma membrane in pollen tubes. AtSUC1 is also expressed in roots and external application of sucrose increased AtSUC1 expression in roots. AtSUC1 is important for sucrose-dependent signaling leading to anthocyanin accumulation in seedlings. suc1 mutants accumulated less anthocyanins in response to exogenous sucrose or maltose and microarray analysis revealed reduced expression of many genes important for anthocyanin biosynthesis. The results indicate that AtSUC1 is important for sugar signaling in vegetative tissue and for normal male gametophyte function.
TL;DR: Consumption of glucose, sucrose or fructose solution results in caloric overconsumption and body weight gain through activation of hunger signals and depression of satiety signals as well as activation of reward components.
TL;DR: Data suggest that a yet-unidentified oxidative pentose phosphate pathway-dependent sugar-sensing pathway governs the regulation of root nitrogen and sulfur acquisition by the carbon status of the plant to coordinate the availability of these three elements for amino acid synthesis.
Abstract: Root ion transport systems are regulated by light and/or sugars, but the signaling mechanisms are unknown. We showed previously that induction of the NRT2.1 NO3− transporter gene by sugars was dependent on carbon metabolism downstream hexokinase (HXK) in glycolysis. To gain further insights on this signaling pathway and to explore more systematically the mechanisms coordinating root nutrient uptake with photosynthesis, we studied the regulation of 19 light-/sugar-induced ion transporter genes. A combination of sugar, sugar analogs, light, and CO2 treatments provided evidence that these genes are not regulated by a common mechanism and unraveled at least four different signaling pathways involved: regulation by light per se, by HXK-dependent sugar sensing, and by sugar sensing upstream or downstream HXK, respectively. More specific investigation of sugar-sensing downstream HXK, using NRT2.1 and NRT1.1 NO3− transporter genes as models, highlighted a correlation between expression of these genes and the concentration of glucose-6-P in the roots. Furthermore, the phosphogluconate dehydrogenase inhibitor 6-aminonicotinamide almost completely prevented induction of NRT2.1 and NRT1.1 by sucrose, indicating that glucose-6-P metabolization within the oxidative pentose phosphate pathway is required for generating the sugar signal. Out of the 19 genes investigated, most of those belonging to the NO3−, NH4+, and SO42− transporter families were regulated like NRT2.1 and NRT1.1. These data suggest that a yet-unidentified oxidative pentose phosphate pathway-dependent sugar-sensing pathway governs the regulation of root nitrogen and sulfur acquisition by the carbon status of the plant to coordinate the availability of these three elements for amino acid synthesis.
TL;DR: Three previously unidentified sugar signalling genes have been identified, showing that ABA and glucose signalling overlap to a larger extend than originally thought.
Abstract: Sugars regulate important processes and affect the expression of many genes in plants. Characterization of Arabidopsis (Arabidopsis thaliana) mutants with altered sugar sensitivity revealed the function of abscisic acid (ABA) signalling in sugar responses. However, the exact interaction between sugar signalling and ABA is obscure. Therefore ABA deficient plants with constitutive ABI4 expression (aba2-1/35S::ABI4) were generated. Enhanced ABI4 expression did not rescue the glucose insensitive (gin) phenotype of aba2 seedlings indicating that other ABA regulated factors are essential as well. Interestingly, both glucose and ABA treatment of Arabidopsis seeds trigger a post-germination seedling developmental arrest. The glucose-arrested seedlings had a drought tolerant phenotype and showed glucose-induced expression of ABSCISIC ACID INSENSITIVE3 (ABI3), ABI5 and LATE EMBRYOGENESIS ABUNDANT (LEA) genes reminiscent of ABA signalling during early seedling development. ABI3 is a key regulator of the ABA-induced arrest and it is shown here that ABI3 functions in glucose signalling as well. Multiple abi3 alleles have a glucose insensitive (gin) phenotype comparable to that of other known gin mutants. Importantly, glucose-regulated gene expression is disturbed in the abi3 background. Moreover, abi3 was insensitive to sugars during germination and showed sugar insensitive (sis) and sucrose uncoupled (sun) phenotypes. Mutant analysis further identified the ABA response pathway genes ENHANCED RESPONSE TO ABA1 (ERA1) and ABI2 as intermediates in glucose signalling. Hence, three previously unidentified sugar signalling genes have been identified, showing that ABA and glucose signalling overlap to a larger extend than originally thought.
TL;DR: It is demonstrated that constitutive expression of AtNHX3 in sugar beet (Beta vulgaris L.) conferred augmented resistance to high salinity on transgenic plants and implicate that AtNHx3 is also a functional antiporter responsible for salt tolerance by mediating K(+)/H(+) exchange in higher plants.
Abstract: In Arabidopsis thaliana, six vacuolar Na(+)/H(+) antiporters (AtNHX1-6) were identified. Among them, AtNHX1, 2 and 5 are functional Na(+)/H(+) antiporters with the most abundant expression levels in seedling shoots and roots. However, the expression of AtNHX3 in Arabidopsis can only be detected by RT-PCR, and its physiological function still remains unclear. In this work, we demonstrate that constitutive expression of AtNHX3 in sugar beet (Beta vulgaris L.) conferred augmented resistance to high salinity on transgenic plants. In the presence of 300 or 500 mm NaCl, transgenic plants showed very high potassium accumulation in the roots and storage roots. Furthermore, the transcripts of sucrose phosphate synthase (SPS), sucrose synthase (SS) and cell wall sucrose invertase (SI) genes were maintained in transgenic plants. The accumulation of soluble sugar in the storage roots of transgenic plants grown under high salt stress condition was also higher. Our results implicate that AtNHX3 is also a functional antiporter responsible for salt tolerance by mediating K(+)/H(+) exchange in higher plants. The salt accumulation in leaves but not in the storage roots, and the increased yield of storage roots with enhanced constituent soluble sugar contents under salt stress condition demonstrate a great potential use of this gene in improving the quality and yield of crop plants.
TL;DR: In this article, the loss of sugar (glucose, fructose, and sucrose) in clarified pineapple juice was evaluated using micro-and ultra-filtration, using two different module geometries (plate/frame and tubular systems) to select the membrane process that would best preserve these nutrients.
TL;DR: In this paper, the influence of molecular sieves concentration on conversion in supercritical carbon dioxide (SC CO2) was studied and the growth inhibitory effect of commercial and enzymatically synthesized sucrose and fructose fatty acid esters on Gram-positive and Gram-negative micro-organisms, as well as on yeast was tested.
Abstract: Lipase-catalyzed synthesis of different sugar fatty acid esters was performed in high yields in 2-methyl-2-butanol at atmospheric pressure and in supercritical carbon dioxide (SC CO2) at 10 MPa. Influence of molecular sieves concentration on conversion in SC CO2 was studied. Growth inhibitory effect of commercial sucrose fatty acid esters and enzymatically synthesized sucrose and fructose fatty acid esters on Gram-positive and Gram-negative micro-organisms, as well as on yeast was tested. Sucrose laurate inhibited the growth of Bacillus cereus food poisoning bacteria at a concentration of 9.375 mg/ml.
TL;DR: High-resolution expression mapping in root tips showed that only a few proton-dependent transport of the STP (Sugar Transport Protein) and SUT/SUC (Sucrose Transporter/Carrier) families are expressed in the external cell layers of root tips, which may help to pinpoint candidate genes for uptake and release of carbohydrates from roots.
Abstract: Although soil contains only traces of soluble carbohydrates, plant roots take up glucose and sucrose efficiently when supplied in artificial media. Soluble carbohydrates and other small metabolites found in soil are in part products from exudation from plant roots. The molecular nature of the transporters for uptake and exudation is unknown. Here, fluorescence resonance energy transfer (FRET) glucose and sucrose sensors were used to characterize accumulation and elimination of glucose and sucrose in Arabidopsis roots tips. Using an improved image acquisition set-up, FRET responses to perfusion with carbohydrates were detectable in roots within less than 10 sec and over a wide concentration range. Accumulation was fully reversible within 10-180 sec after glucose or sucrose had been withdrawn; elimination may be caused by metabolism and/or efflux. The rate of elimination was unaffected by pre-incubation with high concentrations of glucose, suggesting that elimination is not due to accumulation in a short-term buffer such as the vacuole. Glucose and sucrose accumulation was insensitive to protonophores, was comparable in media differing in potassium levels, and was similar at pH 5.8, 6.8 and 7.8, suggesting that both influx and efflux may be mediated by proton-independent transport systems. High-resolution expression mapping in root tips showed that only a few proton-dependent transport of the STP (Sugar Transport Protein) and SUT/SUC (Sucrose Transporter/Carrier) families are expressed in the external cell layers of root tips. The root expression maps may help to pinpoint candidate genes for uptake and release of carbohydrates from roots.
TL;DR: The role of different organic acids in mineral phosphate solubilization by rhizobacteria depending on the nature of the available carbon source is demonstrated.
Abstract: A novel phosphate solubilizing bacterium (PSB) was isolated from the rhizosphere of sugarcane and is capable of utilizing sucrose and rock phosphate as the sole carbon and phosphate source, respectively. This PSB exhibited mineral phosphate solubilizing (MPS) phenotype on sugars such as sucrose and fructose, which are not substrates for enzyme glucose dehydrogenase (GDH), along with GDH substrates, viz., glucose, xylose, and maltose, as carbon sources. PCR amplification of the rRNA gene and sequence analysis identified this bacterium as Citrobacter sp. DHRSS. On sucrose and fructose Citrobacter sp. DHRSS liberated 170 and 100 μM free phosphate from rock phosphate and secreted 49 mM (2.94 g/L) and 35 mM (2.1 g/L) acetic acid, respectively. Growth of Citrobacter sp. DHRSS on sucrose is mediated by an intracellular inducible neutral invertase. Interestingly, in the presence of GDH substrates like glucose and maltose, Citrobacter sp. DHRSS produced approximately 20 mM (4.36 g/L) gluconic acid and phosphate released was 520 and 570 μM, respectively. Citrobacter sp. DHRSS GDH activity was found when grown on GDH and non-GDH substrates, indicating that it is constitutive and could act on a wide range of aldose sugars. This study demonstrates the role of different organic acids in mineral phosphate solubilization by rhizobacteria depending on the nature of the available carbon source.
TL;DR: It was noted that shade modified the expression of SUS-encoding genes in coffee beans; CaSUS2 gene transcripts levels were higher in SH than in FS, which suggests that sucrose metabolism was redirected to other metabolic pathways that need to be identified.
TL;DR: This review examines the hypotheses that developmental programmed cell death in leaves is mediated by sugar starvation in the leaf cells or by sugar accumulation in these cells, and concludes that neither of the two hypotheses is correct.
Abstract: This review examines the hypotheses that developmental programmed cell death in leaves is mediated (i) by sugar starvation in the leaf cells or (ii) by sugar accumulation in these cells. Experimental evidence for both hypotheses is critically discussed and found to be lacking. For example, some papers show that sugars prevent senescence of cut leaves placed in darkness, and prevent low sugar levels in the leaves. In these tests, the sugars seem to replace photosynthesis, hence the results have little relevance to leaf senescence in intact plants in the light. Low nitrogen nutrition and high light results in earlier senescence than the low nitrogen treatment alone. This is accompanied by high sugar levels in the leaves. The results have led to the idea that accumulation of sugars is the cause of the additional effect, or more generally, that sugar accumulation is always the direct cause of leaf senescence. Results from over-expressing, or knocking out, hexokinase genes tend to support the high sugar hypothesis, but pleiotropic effects confound this conclusion. In addition, several experiments show the effects of treatments on senescence without the increase in leaf sugar levels. Nonetheless, sugar levels are usually measured in whole leaves. Such an overall level does not reflect the differences in the onset of senescence between tissues and cells, and can therefore not be used as an argument for or against either of the two hypotheses. It is argued that future work should determine the time line of the concentrations of various sugars in various cells and cellular compartments, in relation to senescence processes in the same cells. Taken together, the data are not decisive. It is possible that neither of the two hypotheses is correct.
TL;DR: It is shown how the three conserved amino acids at the active sites of glucansucrases participate in the polymerization of dextran and related glucans from a single active site by the addition of the D-glucose moiety of sucrose to the reducing-ends of the covalently linked glucan chains in a two catalytic-site, insertion mechanism.
TL;DR: The results showed that the rosemary metabonome was dominated by 33 metabolites including sugars, amino acids, organic acids, polyphenolic acids, and diterpenes, among which quinate, cis-4-glucosyloxycinnamic acid, and 3,4,5-trimethoxyphenylmethanol were found in rosemary for the first time.
Abstract: The molecular compositions of rosemary (Rosmarinus officinalis L.) extracts and their dependence on extraction solvents, seasons, and drying processes were systematically characterized using NMR spectroscopy and multivariate data analysis. The results showed that the rosemary metabonome was dominated by 33 metabolites including sugars, amino acids, organic acids, polyphenolic acids, and diterpenes, among which quinate, cis-4-glucosyloxycinnamic acid, and 3,4,5-trimethoxyphenyl-methanol were found in rosemary for the first time. Compared with water extracts, the 50% aqueous methanol extracts contained higher levels of sucrose, succinate, fumarate, malonate, shikimate, and phenolic acids, but lower levels of fructose, glucose, citrate, and quinate. Chloroform/methanol was an excellent solvent for selective extraction of diterpenes. From February to August, the levels of rosmarinate and quinate increased, whereas the sucrose level decreased. The sun-dried samples contained higher concentrations of rosmarinate, sucrose, and some amino acids but lower concentrations of glucose, fructose, malate, succinate, lactate, and quinate than freeze-dried ones. These findings will fill the gap in the understanding of rosemary composition and its variations.
TL;DR: It is suggested that PFP influences the ability of young, biosynthetically active sugarcane culm tissue to accumulate sucrose but that the equilibrium of the glycolytic intermediates, including the stored sucrose, is restored when ATP-dependent phosphofructokinase and the residual PFP activity is sufficient to sustain the required gly colytic flux as the tissue matures.
Abstract: Pyrophosphate: fructose 6-phosphate 1-phosphotransferase (PFP) activity was successfully down-regulated in sugarcane using constitutively expressed antisense and untranslatable forms of the sugarcane PFP-beta gene. In young internodal tissue activity was reduced by up to 70% while no residual activity could be detected in mature tissues. The transgenic plants showed no visible phenotype or significant differences in growth and development under greenhouse and field conditions. Sucrose concentrations were significantly increased in the immature internodes of the transgenic plants but not in the mature internodes. This contributed to an increase in the purity of the immature tissues, resembling an early ripening phenotype. Both the immature and mature internodes of the transgenic plants had significantly higher fibre contents. These findings suggest that PFP influences the ability of young, biosynthetically active sugarcane culm tissue to accumulate sucrose but that the equilibrium of the glycolytic intermediates, including the stored sucrose, is restored when ATP-dependent phosphofructokinase and the residual PFP activity is sufficient to sustain the required glycolytic flux as the tissue matures. Moreover, it suggests a role for PFP in glycolytic carbon flow, which could be rate limiting under conditions of high metabolic activity.
TL;DR: Glycemic index/glycemic load concepts are attempts to use these carbohydrate availability and amount issues for controlling postprandial glycemia in individuals with diabetes.
Abstract: Both the type and amount of carbohydrate found in foods influence postprandial glucose levels and can also affect overall glycemic control in individuals with diabetes. This review, based on the American Diabetes Association's Nutrition Recommendations and Interventions for Diabetes, and the American Dietetic Association's Evidence Analysis Library (Diabetes 1 and 2), provides a description and interpretation of the clinical studies involving diabetes and type and amount of carbohydrate. Although the relationship between blood glucose and insulin is linear, not all types of carbohydrate are fully metabolized to blood glucose. Added sugars such as sucrose and high fructose corn syrup are digested, absorbed, and fully metabolized in a similar fashion to naturally occurring mono- and disaccharides. Only about half of the carbohydrate grams from sugar alcohols and half or less from dietary fiber are metabolized to glucose whereas almost all "other carbohydrate" (mainly starch such as amylose and amylopectin) becomes blood glucose. The percent of energy as carbohydrate indicated for people with diabetes depends on individual preference, diabetes medication, and weight management goals. Glycemic index/glycemic load concepts are attempts to use these carbohydrate availability and amount issues for controlling postprandial glycemia.
TL;DR: Evidence for the simultaneous operation of two central carbon metabolic pathways was found through the detection of fructose-1,6-bisphosphate aldolase, phosphofructokinase, and phosphoglucoisomerase activities and the presence of phosphorylated EMP and PKP intermediates using in vitro 31P NMR.
Abstract: Metabolic flux analysis indicated that the heterofermentative Lactobacillus reuteri strain ATCC 55730 uses both the Embden-Meyerhof pathway (EMP) and phosphoketolase pathway (PKP) when glucose or sucrose is converted into the three-carbon intermediate stage of glycolysis. In all cases studied, the main flux is through the PKP, while the EMP is used as a shunt. In the exponential growth phase, 70%, 73%, and 84% of the flux goes through the PKP in cells metabolizing (i) glucose plus fructose, (ii) glucose alone, and (iii) sucrose alone, respectively. Analysis of the genome of L. reuteri ATCC 55730 confirmed the presence of the genes for both pathways. Further evidence for the simultaneous operation of two central carbon metabolic pathways was found through the detection of fructose-1,6-bisphosphate aldolase, phosphofructokinase, and phosphoglucoisomerase activities and the presence of phosphorylated EMP and PKP intermediates using in vitro 31P NMR. The maximum specific growth rate and biomass yield obtained on glucose were twice as low as on sucrose. This was the result of low ATP levels being present in glucose-metabolizing cells, although the ATP production flux was as high as in sucrose-metabolizing cells due to a twofold increase of enzyme activities in both glycolytic pathways. Growth performance on glucose could be improved by adding fructose as an external electron acceptor, suggesting that the observed behavior is due to a redox imbalance causing energy starvation.
TL;DR: In this paper, the authors examined changes in sugar metabolism during storage in Japanese pear (Pyrus pyrifolia Nakai cvs. Gold Nijisseiki and Hosui).
TL;DR: It is concluded that high concentrations of solutes accumulated in the mesocarp apoplast prior to veraison, and that P loss was a direct result of decreased ΨsA, which decreased before veraisons, suggesting that apoplastic solutes play an important role in the events of cellular metabolism that lead to the onset of ripening.
Abstract: In Vitis vinifera L. berries, the onset of ripening (known as “veraison”) involves loss of turgor (P) in the mesocarp cells. We hypothesized that P loss was associated with an accumulation of apoplastic solutes in mesocarp tissue prior to veraison. Apoplastic sap was extracted from the mesocarp by centrifugation at the appropriate gravity to measure the apoplast solute potential (ΨsA) and assay the sap composition. The ΨsA was about −0.2 MPa early in development, decreased about 1.0 MPa by veraison, and continued to decrease during ripening to almost −4.0 MPa by the end of berry development. Potassium, malate, tartrate, proline, glucose, fructose, and sucrose were quantified in apoplastic sap. The calculated contribution of these solutes was about 50% of the total ΨsA preveraison, but increased to about 75% as fructose and glucose accumulated during ripening. The contribution of the estimated matric potential to apoplast water potential decreased during development and was only 1.5% postveraison. We conclude that high concentrations of solutes accumulated in the mesocarp apoplast prior to veraison, and that P loss was a direct result of decreased ΨsA. Because ΨsA decreased before veraison, our findings suggest that apoplast solutes play an important role in the events of cellular metabolism that lead to the onset of ripening.
TL;DR: In this article, the main soluble sugars in A. deliciosa and A. rufa fruits were glucose and fructose, although sucrose was present in smaller amounts, while myo-inositol contents were 0.575-0.982 g/100 g fresh weight.
Abstract: Soluble sugars, sugar alcohol, and organic acid contents in Actinidia fruits at the eating-ripe stage were determined in various genotypes using high-performance liquid chromatography: five A. deliciosa, seven A. chinensis, two A. rufa, eight A. arguta, and three interspecific hybrids. The main soluble sugars in A. deliciosa and A. rufa fruits were glucose and fructose, although sucrose was present in smaller amounts. In contrast, sucrose was the predominant sugar in A. arguta fruits, followed by fructose and glucose. Most Actinidia fruits tested here contained myo-inositol as a sugar alcohol component. In particular, myo-inositol contents in A. arguta fruits were 0.575–0.982 g/100 g fresh weight, which is the highest level among all foods. Regarding the organic acid component, citric and quinic acids predominated over malic acid in all Actinidia fruits tested. Compared to A. deliciosa and A. chinensis, the proportion of quinic acid was higher in A. rufa and lower in A. arguta.
TL;DR: Hexose translocation is to be regarded as a normal mode of carbohydrate transfer by the phloem equivalent to that of sucrose, raffinose-family sugars, or sugar alcohols.
Abstract: According to most textbooks, only non-reducing carbohydrate species such as sucrose, sugar alcohols, and raffinose-family sugars function as phloem translocates. Occasional abundance of reducing sugar species (such as hexoses) in sieve-tube sap has been discarded as an experimental artefact. This study, however, discloses a widespread occurrence of hexoses in the sieve-tube sap. Phloem exudation facilitated by EDTA provided evidence that many of the members of two plant families (Ranunculaceae and Papaveraceae) investigated translocate >80% of carbohydrates in the form of hexoses. Representatives of other families also appear to translocate appreciable amounts of hexoses in the sieve tubes. Promoting effects of EDTA, activities of sucrose-degrading enzymes, and sugar uptake by micro-organisms on hexose contents of phloem exudates were checked. The rate of sucrose degradation is far too low to explain the large proportions of hexoses measured in phloem exudates; nor did other factors tested seem to stimulate the occurrence of hexoses. The validity of the approach is further supported by the virtual absence of hexoses in exudates from species that were known as exclusive sucrose transporters. This study urges a rethink of the existing views on carbohydrate transport species in the phloem stream. Hexose translocation is to be regarded as a normal mode of carbohydrate transfer by the phloem equivalent to that of sucrose, raffinose-family sugars, or sugar alcohols.