The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform
Abhaya M Dandekar - One of the best experts on this subject based on the ideXlab platform.
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sugar metabolism and accumulation in the fruit of transgenic apple trees with decreased Sorbitol synthesis
Horticulture research, 2018Co-Authors: Abhaya M Dandekar, Mingjun Li, Pengmin Li, Lailiang ChengAbstract:Both Sorbitol and sucrose are synthesized in source leaves and transported to fruit for supporting fruit growth in tree fruit species of the Rosaceae family. In apple (Malus domestica), antisense suppression of aldose-6-phosphate reductase, the key enzyme for Sorbitol synthesis, significantly decreased the Sorbitol concentration but increased the sucrose concentration in leaves, leading to a lower Sorbitol but a higher sucrose supply to fruit in these plants. In response to this altered carbon supply, the transgenic fruit had lower concentration of Sorbitol and much higher concentration of glucose but similar levels of fructose, sucrose, and starch throughout fruit development relative to the untransformed control. Activities of Sorbitol dehydrogenase, fructokinase, and sucrose phosphate synthase were lower, whereas activities of neutral invertase, sucrose synthase, and hexokinase were higher in the transgenic fruit during fruit development. Transcript levels of MdSOT1, MdSDHs, MdFK2, and MdSPS3/6 were downregulated, whereas transcript levels of MdSUC1/4, MdSUSY1-3, MdNIV1/3, MdHKs, and MdTMT1 were upregulated in the transgenic fruit. These findings suggest that the Sucrose cycle and the sugar transport system are very effective in maintaining the level of fructose and provide insights into the roles of Sorbitol and sucrose in regulating sugar metabolism and accumulation in Sorbitol-synthesizing species. Analysis of the sugar metabolism and transport system in apple trees shows how the fruit fructose level and fruit production is largely maintained in response to decreased Sorbitol synthesis in leaves. Disruption to developmental processes and environmental factors can alter the supply of sugars from leaves to fruit. Lailiang Cheng at Cornell University, New York, US, and co-workers examined sugar metabolism and transport in modified apple trees to ascertain how a deficiency in one sugar, Sorbitol, influences fruit development and sugar accumulation. Ordinarily, fructose—the sugar that generates sweeter fruit—is mainly derived from Sorbitol. The modified trees compensated for Sorbitol loss by increasing their sucrose supply and converting the excess sucrose into fructose and glucose, largely sustaining fruit production and fructose level. The team’s results demonstrate the metabolic flexibility of the sugar cycle in fleshy fruits.
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silencing leaf Sorbitol synthesis alters long distance partitioning and apple fruit quality
Proceedings of the National Academy of Sciences of the United States of America, 2006Co-Authors: Yasuo Suzuki, Sandie L Uratsu, Bruce D Lampinen, Nichole Ormonde, William K Hu, T M Dejong, Abhaya M DandekarAbstract: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.
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Sorbitol Synthesis in Transgenic Tobacco with Apple cDNA Encoding NADP-Dependent Sorbitol-6-Phosphate Dehydrogenase
Plant and Cell Physiology, 1995Co-Authors: Sandra L. Uratsu, Abhaya M DandekarAbstract:: The apple (Malus domestica) cDNA encoding NADP-dependent Sorbitol-6-phosphate dehydrogenase (S6PDH) was stably integrated and expressed in transgenic tobacco (Nicotiana tabacum cv. SR1). Expression of the cDNA in either a sense or antisense orientation was accomplished using cauliflower mosaic virus regulatory sequences (CaMV35S). Sorbitol synthesis was confirmed by gas-chromatography-mass-spectroscopy (GC-MS). Sorbitol concentration in the leaves of the transgenic plants expressing the sense orientation varied from 186 to 446 nmol (g fr wt)-1. The concentration positively correlates with S6PDH activity in leaves. Neither Sorbitol nor S6PDH activity was detected in the extracts of nontransformed tobacco or transgenic tobacco expressing the antisense orientation. These results provide key genetic evidence that S6PDH expression is sufficient for the synthesis of Sorbitol in tobacco, implicating it as a key enzyme in the Sorbitol biosynthetic pathway in apple and perhaps other members of the woody Rosaceae.
Hening Hu - One of the best experts on this subject based on the ideXlab platform.
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phloem mobility of boron is species dependent evidence for phloem mobility in Sorbitol rich species
Annals of Botany, 1996Co-Authors: Patrick H Brown, Hening HuAbstract:Boron is generally considered to be phloem immobile or to have only limited phloem mobility in higher plants. Evidence suggests, however, that B may be mobile in some species within thePyrus, MalusandPrunusgenera. These genera utilize Sorbitol as a primary translocated photosynthate and it has been clearly demonstrated that B forms stable complexes with Sorbitolin vitro.In the research presented here we demonstrate, further, that B is freely phloem mobile inPyrus, MalusandPrunusspecies and suggest that this is mediated by the formation and transport of B-Sorbitol complexes. The pattern of B distribution within shoot organs and the translocation of foliar-applied, isotopically-enriched10B was studied in six tree species. Results demonstrate that in species in which Sorbitol is a major sugar (Sorbitol-rich), B is freely mobile while in species that produce little or no Sorbitol (Sorbitol-poor) B is largely immobile. The Sorbitol-rich species used here were almond [Prunus amygdalusB. syn.P. dulcis(Mill.)], apple (Malus domesticaB.) and nectarine (Prunus persicaL. B. var.nectarinaM.), Sorbitol-poor species included fig (Ficus caricaL.), pistachio (Pistacia veraL.) and walnut (Juglans regiaL.). In Sorbitol-rich species foliar applied10B was transported from the treated leaves to adjacent fruit and specifically to the fruit tissues (hull, shell or kernel) that developed during the experimental period. Whereas, foliar-applied10B was rapidly translocated out of leaves, only a small percentage of the11B present in the leaf at the time of foliar application was retranslocated. In Sorbitol-rich species, B concentrations differed only slightly between old and young leaves while fruit tissue had significantly greater B concentrations than leaves. In contrast, Sorbitol-poor species had significantly higher B concentrations in older leaves than young leaves while fruit tissue had the lowest B concentration. This occurred irrespective the source of plant B (soil, solution or foliar-applied). In a subsequent experiment the growth of apple trees in solutions free of applied B was maintained solely by foliar applications of B to mature leaves. These results indicate that B is mobile in species that produce significant amounts of Sorbitol. We propose that the mobility of B in these species is mediated by the formation of B-Sorbitol complexes.
Patrick H Brown - One of the best experts on this subject based on the ideXlab platform.
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phloem mobility of boron is species dependent evidence for phloem mobility in Sorbitol rich species
Annals of Botany, 1996Co-Authors: Patrick H Brown, Hening HuAbstract:Boron is generally considered to be phloem immobile or to have only limited phloem mobility in higher plants. Evidence suggests, however, that B may be mobile in some species within thePyrus, MalusandPrunusgenera. These genera utilize Sorbitol as a primary translocated photosynthate and it has been clearly demonstrated that B forms stable complexes with Sorbitolin vitro.In the research presented here we demonstrate, further, that B is freely phloem mobile inPyrus, MalusandPrunusspecies and suggest that this is mediated by the formation and transport of B-Sorbitol complexes. The pattern of B distribution within shoot organs and the translocation of foliar-applied, isotopically-enriched10B was studied in six tree species. Results demonstrate that in species in which Sorbitol is a major sugar (Sorbitol-rich), B is freely mobile while in species that produce little or no Sorbitol (Sorbitol-poor) B is largely immobile. The Sorbitol-rich species used here were almond [Prunus amygdalusB. syn.P. dulcis(Mill.)], apple (Malus domesticaB.) and nectarine (Prunus persicaL. B. var.nectarinaM.), Sorbitol-poor species included fig (Ficus caricaL.), pistachio (Pistacia veraL.) and walnut (Juglans regiaL.). In Sorbitol-rich species foliar applied10B was transported from the treated leaves to adjacent fruit and specifically to the fruit tissues (hull, shell or kernel) that developed during the experimental period. Whereas, foliar-applied10B was rapidly translocated out of leaves, only a small percentage of the11B present in the leaf at the time of foliar application was retranslocated. In Sorbitol-rich species, B concentrations differed only slightly between old and young leaves while fruit tissue had significantly greater B concentrations than leaves. In contrast, Sorbitol-poor species had significantly higher B concentrations in older leaves than young leaves while fruit tissue had the lowest B concentration. This occurred irrespective the source of plant B (soil, solution or foliar-applied). In a subsequent experiment the growth of apple trees in solutions free of applied B was maintained solely by foliar applications of B to mature leaves. These results indicate that B is mobile in species that produce significant amounts of Sorbitol. We propose that the mobility of B in these species is mediated by the formation of B-Sorbitol complexes.
María J. Yebra - One of the best experts on this subject based on the ideXlab platform.
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Sorbitol production from lactose by engineered Lactobacillus casei deficient in Sorbitol transport system and mannitol-1-phosphate dehydrogenase.
Applied Microbiology and Biotechnology, 2009Co-Authors: Reinout De Boeck, Luz Adriana Sarmiento-rubiano, Inmaculada Nadal, Vicente Monedero, Gaspar Pérez-martínez, María J. YebraAbstract:Sorbitol is a sugar alcohol largely used in the food industry as a low-calorie sweetener. We have previously described a Sorbitol-producing Lactobacillus casei (strain BL232) in which the gutF gene, encoding a Sorbitol-6-phosphate dehydrogenase, was expressed from the lactose operon. Here, a complete deletion of the ldh1 gene, encoding the main l-lactate dehydrogenase, was performed in strain BL232. In a resting cell system with glucose, the new strain, named BL251, accumulated Sorbitol in the medium that was rapidly metabolized after glucose exhaustion. Reutilization of produced Sorbitol was prevented by deleting the gutB gene of the phosphoenolpyruvate: Sorbitol phosphotransferase system (PTSGut) in BL251. These results showed that the PTSGut did not mediate Sorbitol excretion from the cells, but it was responsible for uptake and reutilization of the synthesized Sorbitol. A further improvement in Sorbitol production was achieved by inactivation of the mtlD gene, encoding a mannitol-1-phosphate dehydrogenase. The new strain BL300 (lac::gutF Δldh1 ΔgutB mtlD) showed an increase in Sorbitol production whereas no mannitol synthesis was detected, avoiding thus a polyol mixture. This strain was able to convert lactose, the main sugar from milk, into Sorbitol, either using a resting cell system or in growing cells under pH control. A conversion rate of 9.4% of lactose into Sorbitol was obtained using an optimized fed-batch system and whey permeate, a waste product of the dairy industry, as substrate.
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dietary supplementation with Sorbitol results in selective enrichment of lactobacilli in rat intestine
Research in Microbiology, 2007Co-Authors: Luz Adriana Sarmientorubiano, Gaspar Perezmartinez, Manuel Zuniga, María J. YebraAbstract:A potential prebiotic action has been ascribed to Sorbitol, but in vivo evidence of this remains scarce. In the present work, the effect of Sorbitol was compared to that of fructo-oligosaccharides (FOS) in a rat model. Microbiota changes, particularly in lactobacilli, were analyzed on fecal, colonic and cecal samples. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene amplicons using universal primers showed that FOS and Sorbitol diets exerted a strong influence upon gut microbiota patterns. When Lactobacillus group-specific primers were used, DGGE profiles revealed five DNA bands that belonged to Lactobacillus johnsonii, Lactobacillus sp. AD102, Lactobacillus intestinalis, Lactobacillus murinus and Lactobacillus reuteri. Although these species are present in all dietary groups, quantification by real-time PCR showed that Sorbitol and FOS intake increased L. reuteri cell numbers, and Sorbitol also contributed to maintaining the levels of Lactobacillus sp. AD102. Analysis of organic acid concentrations showed that Sorbitol intake significantly increased colonic and cecal butyrate levels. Hence, Sorbitol, which is widely used as a low-calorie sweetener, has the capacity, in our animal model, to modify gut microbiota activity in such a way as to possibly contribute to healthy colonic mucosa.
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cross talk between the l sorbose and d Sorbitol d glucitol metabolic pathways in lactobacillus casei
Microbiology, 2002Co-Authors: María J. Yebra, Gaspar PerezmartinezAbstract:A gene encoding Sorbitol-6-phosphate dehydrogenase (SorF) belonging to the sorbose operon (sorFABCDG) has been characterized in Lactobacillus casei. Inactivation of this gene revealed the presence of another Sorbitol-6-phosphate dehydrogenase that was induced by D-Sorbitol (D-glucitol). The gene encoding this activity (gutF) has also been isolated, sequenced and disrupted. The Sorbitol-6-phosphate dehydrogenase genes (sorF, gutF) were required for growth on L-sorbose and D-Sorbitol, respectively. Biochemical and transcriptional analyses of the wild-type and mutant strains demonstrated that L-sorbose and D-Sorbitol induced sorF and the gene encoding the sorbose operon activator (sorR), while the expression of gutF was only activated by D-Sorbitol. Furthermore, these studies indirectly suggested that a common metabolite of the L-sorbose and D-Sorbitol metabolic pathways (probably D-Sorbitol 6-phosphate) would act as the effector of SorR. The same effector would also be the inducer of gutF, although the two pathways seem to be subject to distinct regulatory mechanisms.
I A Carlos - One of the best experts on this subject based on the ideXlab platform.
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study of an alkaline bath for tin deposition in the presence of Sorbitol and physical and morphological characterization of tin film
Journal of Applied Electrochemistry, 2006Co-Authors: R L Broggi, G M De Oliveira, L L Barbosa, E M J A Pallone, I A CarlosAbstract:Effects of Sorbitol concentration on the deposition of tin on to platinum were studied by cyclic voltammetry. It was observed that Sorbitol affected the tin-plating rate and also the thermodynamics of the deposition process. Rotating disk electrode studies showed that the deposition rate is controlled by mass transport and that the diffusion coefficient of the Sn(II) complex decreases with increasing Sorbitol concentration. The presence of Sorbitol in the plating bath was beneficial since a plating current efficiency of ∼70% was obtained, while in its absence it was ∼19%. Scanning electron microscopy showed that Sorbitol works as a brightener since tin crystallites were much smaller than those obtained from alkaline solution in the absence of Sorbitol. Also, at 1.0 M, Sorbitol produced a very smooth film. X-ray spectra showed that β-Sn was deposited.
