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Uwe Sonnewald - One of the best experts on this subject based on the ideXlab platform.
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regulation of cell wall bound invertase in pepper leaves by xanthomonas campestris pv vesicatoria type three effectors
PLOS ONE, 2012Co-Authors: Sophia Sonnewald, Johannes Peter Roman Priller, Julia Schuster, Eric Glickmann, Mohammedreza Hajirezaei, Stefan Siebig, Mary Beth Mudgett, Uwe SonnewaldAbstract:Xanthomonas campestris pv. vesicatoria (Xcv) possess a type 3 secretion system (T3SS) to deliver effector proteins into its Solanaceous host plants. These proteins are involved in suppression of plant defense and in reprogramming of plant metabolism to favour bacterial propagation. There is increasing evidence that Hexoses contribute to defense responses. They act as substrates for metabolic processes and as metabolic semaphores to regulate gene expression. Especially an increase in the apoplastic hexose-to-sucrose ratio has been suggested to strengthen plant defense. This shift is brought about by the activity of cell wall-bound invertase (cw-Inv). We examined the possibility that Xcv may employ type 3 effector (T3E) proteins to suppress cw-Inv activity during infection. Indeed, pepper leaves infected with a T3SS-deficient Xcv strain showed a higher level of cw-Inv mRNA and enzyme activity relative to Xcv wild type infected leaves. Higher cw-Inv activity was paralleled by an increase in Hexoses and mRNA abundance for the pathogenesis-related gene PRQ. These results suggest that Xcv suppresses cw-Inv activity in a T3SS-dependent manner, most likely to prevent sugar-mediated defense signals. To identify Xcv T3Es that regulate cw-Inv activity, a screen was performed with eighteen Xcv strains, each deficient in an individual T3E. Seven Xcv T3E deletion strains caused a significant change in cw-Inv activity compared to Xcv wild type. Among them, Xcv lacking the xopB gene (Xcv ΔxopB) caused the most prominent increase in cw-Inv activity. Deletion of xopB increased the mRNA abundance of PRQ in Xcv ΔxopB-infected pepper leaves, but not of Pti5 and Acre31, two PAMP-triggered immunity markers. Inducible expression of XopB in transgenic tobacco inhibited Xcv-mediated induction of cw-Inv activity observed in wild type plants and resulted in severe developmental phenotypes. Together, these data suggest that XopB interferes with cw-Inv activity in planta to suppress sugar-enhanced defense responses during Xcv infection.
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regulation of arbuscular mycorrhization by carbon the symbiotic interaction cannot be improved by increased carbon availability accomplished by root specifically enhanced invertase activity
Plant Physiology, 2007Co-Authors: Sara Schaarschmidt, Uwe Sonnewald, Maricruz Gonzalez, Thomas Roitsch, Dieter Strack, Bettina HauseAbstract:The mutualistic interaction in arbuscular mycorrhiza (AM) is characterized by an exchange of mineral nutrients and carbon. The major benefit of AM, which is the supply of phosphate to the plant, and the stimulation of mycorrhization by low phosphate fertilization has been well studied. However, less is known about the regulatory function of carbon availability on AM formation. Here the effect of enhanced levels of Hexoses in the root, the main form of carbohydrate used by the fungus, on AM formation was analyzed. Modulation of the root carbohydrate status was performed by expressing genes encoding a yeast (Saccharomyces cerevisiae)-derived invertase, which was directed to different subcellular locations. Using tobacco (Nicotiana tabacum) alc∷cwINV plants, the yeast invertase was induced in the whole root system or in root parts. Despite increased hexose levels in these roots, we did not detect any effect on the colonization with Glomus intraradices analyzed by assessment of fungal structures and the level of fungus-specific palmitvaccenic acid, indicative for the fungal carbon supply, or the plant phosphate content. Roots of Medicago truncatula, transformed to express genes encoding an apoplast-, cytosol-, or vacuolar-located yeast-derived invertase, had increased hexose-to-sucrose ratios compared to β-glucuronidase-transformed roots. However, transformations with the invertase genes did not affect mycorrhization. These data suggest the carbohydrate supply in AM cannot be improved by root-specifically increased hexose levels, implying that under normal conditions sufficient carbon is available in mycorrhizal roots. In contrast, tobacco rolC∷ppa plants with defective phloem loading and tobacco pyk10∷InvInh plants with decreased acid invertase activity in roots exhibited a diminished mycorrhization.
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systemic acquired resistance mediated by the ectopic expression of invertase possible hexose sensing in the secretory pathway
The Plant Cell, 1996Co-Authors: Karin Herbers, Philippe Meuwly, Wolf B Frommer, Jeanpierre Metraux, Uwe SonnewaldAbstract:Systemic acquired resistance (SAR) has been reported to be associated with lesion-mimic mutants. Tobacco plants expressing vacuolar and apoplastic yeast-derived invertase (vaclnv and cwlnv, respectively) develop spontaneous necrotic lesions similar to hypersensitive responses caused by avirulent pathogens. Therefore, SAR and metabolic alterations leading to the activation of defense-related responses were studied in these plants. Defense-related gene transcripts, callose content, peroxidase activities, and levels of salicylic acid were found to be elevated. The defense reactions were accompanied by increased resistance toward potato virus Y and were measured as decreased viral spreading and reduced multiplication in systemic leaves of the transgenic plants. Interestingly, the accumulation of pathogenesis-related (PR) protein transcripts (PR-Q) and repression of photosynthetic gene transcripts (chlorophyll a/b binding protein) were inversely correlated and required the same threshold level of Hexoses for induction and repression. Expression of a cytosolic yeast-derived invertase in transgenic tobacco plants with equally increased levels of sugars neither displayed SAR responses nor showed decreased levels of photosynthetic genes. It is suggested that hexose sensing in the secretory pathway is essential for mediating the activation of defense-related genes as well as repression of photosynthetic genes in vaclnv and cwlnv plants.
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Cloning and expression analysis of the plastidic fructose-1,6-bisphosphatase coding sequence from potato: circumstantial evidence for the import of Hexoses into chloroplasts
Planta, 1992Co-Authors: Jens Koßmann, Bernd Müller-röber, Tristan A. Dyer, Christine A. Raines, Uwe Sonnewald, Lothar WillmitzerAbstract:A copy DNA encoding the plastid-located isoform of the fructose-1,6-bisphosphatase (cp-FBPase) has been cloned from potato ( Solanum tuberosum L.). Sequence analysis reveals a high degree of homology to cp-FBPases from wheat, spinach, and Arabidopsis . Analysis of RNA blots shows that the expression of the cp-FBPase is limited to green tissue such as leaf and stem, and is absent from photosynthetically inactive tissue such as roots, tubers and stolons. This provides additional evidence that Hexoses or hexose phosphates are imported into amyloplasts of heterotrophic tissues. Incubation of detached leaves of potato in darkness in a sucrosecontaining medium leads to massive accumulation of both starch and transcripts encoding starch biosynthetic enzymes. However, no transcripts encoding the cp-FBPase are detectable under these conditions.
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Inorganic pyrophosphate content and metabolites in potato and tobacco plants expressing E. coli pyrophosphatase in their cytosol.
Planta, 1992Co-Authors: Till Jelitto, Uwe Sonnewald, Lothar Willmitzer, Mohammad Hajirezeai, Mark StittAbstract:Metabolite levels and carbohydrates were investigated in the leaves of tobacco (Nicotiana tabacum L.) and leaves and tubers of potato (Solanum tuberosum L.) plants which had been transformed with pyrophosphatase from Escherichia coli. In tobacco the leaves contained two- to threefold less pyrophosphate than controls and showed a large increase in UDP-glucose, relative to hexose phosphate. There was a large accumulation of sucrose, Hexoses and starch, but the soluble sugars increased more than starch. Growth of the stem and roots was inhibited and starch, sucrose and Hexoses accumulated. In potato, the leaves contained two- to threefold less pyrophosphate and an increased UDP-glucose/ hexose-phosphate ratio. Sucrose increased and starch decreased. The plants produced a larger number of smaller tubers which contained more sucrose and less starch. The tubers contained threefold higher UDP-glucose, threefold lower hexose-phosphates, glycerate-3-phosphate and phosphoenolpyruvate, and up to sixfold more fructose-2,6-bisphosphatase than the wild-type tubers. It is concluded that removal of pyrophosphate from the cytosol inhibits plant growth. It is discussed how these results provide evidence that sucrose mobilisation via sucrose synthase provides one key site at which pyrophosphate is needed for plant growth, but is certainly not the only site at which pyrophosphate plays a crucial role.
Eckhard Boles - One of the best experts on this subject based on the ideXlab platform.
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mammalian glucose permease glut1 facilitates transport of arsenic trioxide and methylarsonous acid
Biochemical and Biophysical Research Communications, 2006Co-Authors: Zijuan Liu, Eckhard Boles, Scott M Landfear, Marco A Sanchez, Xuan Jiang, Barry P. RosenAbstract:Arsenic exposure is associated with hypertension, diabetes, and cancer. Some mammals methylate arsenic. Saccharomyces cerevisiae hexose permeases catalyze As(OH)(3) uptake. Here, we report that mammalian glucose transporter GLUT1 catalyzes As(OH)(3) and CH(3)As(OH)(2) uptake in yeast or in Xenopus laevis oocytes. Expression of GLUT1 in a yeast lacking other glucose transporters allows for growth on glucose. Yeast expressing yeast HXT1 or rat GLUT1 transport As(OH)(3) and CH(3)As(OH)(2). The K(m) of GLUT1 is to 1.2mM for CH(3)As(OH)(2), compared to a K(m) of 3mM for glucose. Inhibition between glucose and CH(3)As(OH)(2) is noncompetitive, suggesting differences between the translocation pathways of Hexoses and arsenicals. Both human and rat GLUT1 catalyze uptake of both As(OH)(3) and CH(3)As(OH)(2) in oocytes. Thus GLUT1 may be a major pathway uptake of both inorganic and methylated arsenicals in erythrocytes or the epithelial cells of the blood-brain barrier, contributing to arsenic-related cardiovascular problems and neurotoxicity.
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arsenic trioxide uptake by hexose permeases in saccharomyces cerevisiae
Journal of Biological Chemistry, 2004Co-Authors: Zijuan Liu, Eckhard Boles, Barry P. RosenAbstract:Arsenic trioxide is a toxic metalloid and carcinogen that is also used as an anticancer drug, and for this reason it is important to identify the routes of arsenite uptake by cells. In this study the ability of hexose transporters to facilitate arsenic trioxide uptake in Saccharomyces cerevisiae was examined. In the absence of glucose, strains with disruption of the arsenite efflux gene ACR3 accumulated high levels of (73)As(OH)(3). The addition of glucose inhibited uptake by approximately 80%. Disruption of FPS1, the aquaglyceroporin gene, reduced glucose-independent uptake by only about 25%, and the residual uptake was nearly completely inhibited by Hexoses, including glucose, galactose, mannose, and fructose but not pentoses or disaccharides. A strain lacking FPS1, ACR3, and all genes for hexose permeases except for HXT3, HXT6, HXT7, and GAL2 exhibited hexose-inhibitable (73)As(OH)(3) uptake, whereas a strain lacking all 18 hexose transport-related genes (HXT1 to HXT17 and GAL2), FPS1 and ACR3, exhibited <10% of wild type (73)As(OH)(3) transport. When HXT1, HXT3, HXT4, HXT5, HXT7, or HXT9 was individually expressed in that strain, hexose-inhibitable (73)As(OH)(3) uptake was restored. In addition, the transport of [(14)C]glucose was inhibited by As(OH)(3). These results clearly demonstrate that hexose permeases catalyze the majority of the transport of the trivalent metalloid arsenic trioxide.
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concurrent knock out of at least 20 transporter genes is required to block uptake of Hexoses in saccharomyces cerevisiae
FEBS Letters, 1999Co-Authors: Roman Wieczorke, Stefanie Krampe, Thomas Weierstall, Kerstin Freidel, Cornelis P Hollenberg, Eckhard BolesAbstract:The hexose transporter family of Saccharomyces cerevisiae comprises 18 proteins (Hxt1–17, Gal2). Here, we demonstrate that all these proteins, except Hxt12, and additionally three members of the maltose transporter family (Agt1, Ydl247, Yjr160) are able to transport Hexoses. In a yeast strain deleted for HXT1–17, GAL2, AGT1, YDL247w and YJR160c, glucose consumption and transport activity were completely abolished. However, as additional deletion of the glucose sensor gene SNF3 partially restored growth on Hexoses, our data indicate the existence of even more proteins able to transport Hexoses in yeast.
Barry P. Rosen - One of the best experts on this subject based on the ideXlab platform.
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mammalian glucose permease glut1 facilitates transport of arsenic trioxide and methylarsonous acid
Biochemical and Biophysical Research Communications, 2006Co-Authors: Zijuan Liu, Eckhard Boles, Scott M Landfear, Marco A Sanchez, Xuan Jiang, Barry P. RosenAbstract:Arsenic exposure is associated with hypertension, diabetes, and cancer. Some mammals methylate arsenic. Saccharomyces cerevisiae hexose permeases catalyze As(OH)(3) uptake. Here, we report that mammalian glucose transporter GLUT1 catalyzes As(OH)(3) and CH(3)As(OH)(2) uptake in yeast or in Xenopus laevis oocytes. Expression of GLUT1 in a yeast lacking other glucose transporters allows for growth on glucose. Yeast expressing yeast HXT1 or rat GLUT1 transport As(OH)(3) and CH(3)As(OH)(2). The K(m) of GLUT1 is to 1.2mM for CH(3)As(OH)(2), compared to a K(m) of 3mM for glucose. Inhibition between glucose and CH(3)As(OH)(2) is noncompetitive, suggesting differences between the translocation pathways of Hexoses and arsenicals. Both human and rat GLUT1 catalyze uptake of both As(OH)(3) and CH(3)As(OH)(2) in oocytes. Thus GLUT1 may be a major pathway uptake of both inorganic and methylated arsenicals in erythrocytes or the epithelial cells of the blood-brain barrier, contributing to arsenic-related cardiovascular problems and neurotoxicity.
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arsenic trioxide uptake by hexose permeases in saccharomyces cerevisiae
Journal of Biological Chemistry, 2004Co-Authors: Zijuan Liu, Eckhard Boles, Barry P. RosenAbstract:Arsenic trioxide is a toxic metalloid and carcinogen that is also used as an anticancer drug, and for this reason it is important to identify the routes of arsenite uptake by cells. In this study the ability of hexose transporters to facilitate arsenic trioxide uptake in Saccharomyces cerevisiae was examined. In the absence of glucose, strains with disruption of the arsenite efflux gene ACR3 accumulated high levels of (73)As(OH)(3). The addition of glucose inhibited uptake by approximately 80%. Disruption of FPS1, the aquaglyceroporin gene, reduced glucose-independent uptake by only about 25%, and the residual uptake was nearly completely inhibited by Hexoses, including glucose, galactose, mannose, and fructose but not pentoses or disaccharides. A strain lacking FPS1, ACR3, and all genes for hexose permeases except for HXT3, HXT6, HXT7, and GAL2 exhibited hexose-inhibitable (73)As(OH)(3) uptake, whereas a strain lacking all 18 hexose transport-related genes (HXT1 to HXT17 and GAL2), FPS1 and ACR3, exhibited <10% of wild type (73)As(OH)(3) transport. When HXT1, HXT3, HXT4, HXT5, HXT7, or HXT9 was individually expressed in that strain, hexose-inhibitable (73)As(OH)(3) uptake was restored. In addition, the transport of [(14)C]glucose was inhibited by As(OH)(3). These results clearly demonstrate that hexose permeases catalyze the majority of the transport of the trivalent metalloid arsenic trioxide.
Yan Zhao - One of the best experts on this subject based on the ideXlab platform.
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combined supercritical and subcritical conversion of cellulose for fermentable hexose production in a flow reaction system
Chemical Engineering Journal, 2011Co-Authors: Yan Zhao, Hongtao Wang, Hao WangAbstract:Abstract Using research on a batch system as basis, a flow reactor was designed and applied in the combined supercritical and subcritical hydrolysis of cellulose for fermentable hexose production. The results show that when the supercritical parameters were maintained, the hexose yield first increased with the rise in subcritical temperature, and then decreased after the maximum yield was obtained. This maximum yield of fermentable Hexoses from cellulose was 31.5% ± 1.4%, which was obtained under the following conditions: cellulose concentration of 3.53 ± 0.24 g L −1 , supercritical temperature of 380 °C, supercritical reaction time of 9.70 ± 0.66 s, subcritical temperature of 240 °C, and subcritical reaction time of 48.49 ± 3.31 s. The appropriate ranges of cellulose concentration (around 3.5 g L −1 ) and reaction time (9–10 s for supercritical process and 45–50 s for subcritical process), which depended on the flows of water and material sludge, were also crucial in obtaining a high hexose yield. Compared with the batch system, the flow reaction system can yield a reasonable amount of hexose from cellulose hydrolysis and proved to be considerably promising for practical applications, especially for combined supercritical and subcritical technology on lignocellulosic resources.
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fermentable hexose production from corn stalks and wheat straw with combined supercritical and subcritical hydrothermal technology
Bioresource Technology, 2009Co-Authors: Yan Zhao, Hongtao Wang, Jinlong YangAbstract:Abstract Lignocellulosic wastes, including corn stalks and wheat straw, were pretreated and hydrolyzed with combined supercritical and subcritical hydrothermal technology. Soluble sugars were collected by pre-washing the crushed materials before hydrolysis. The effects of solid–liquid ratio, temperature, and reaction time on oligosaccharide production were investigated and the optimum supercritical conditions were found to be 20 mg/2.5 ml water, 384 °C, 17 s for corn stalks and 20 mg/2.5 ml water, 384 °C, 19 s for wheat straw. Subsequent subcritical processing of the hydrolyzate (with or without the water extract) from supercritical treatment was guided by a previous analysis of cellulose hydrolysis kinetics. The highest yield of fermentable Hexoses from corn stalks (27.4% of raw material) was obtained at 280 °C, 27 s, and from wheat straw (6.7% of raw material) at 280 °C, 54 s. This study provides novel key parameters for fermentable hexose production from lignocellulosic feedstocks using combined supercritical and subcritical hydrothermal treatment.
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combined supercritical and subcritical process for cellulose hydrolysis to fermentable Hexoses
Environmental Science & Technology, 2009Co-Authors: Yan Zhao, Hongtao WangAbstract:A combined supercritical and subcritical process for pretreatment and hydrolysis of lignocellulosic waste has been proposed. Batch experiments and kinetic analysis were performed to investigate the secondary hydrolysis of cellulose in subcritical water as well as the feasibility of combining the whole process. A 60 mg amount of microcrystalline cellulose and 2.5 mL of deionized water were mixed in each reactor and reacted at 380 °C and 16 s as the primary hydrolysis, followed by different subcritical conditions for secondary hydrolysis. The products were analyzed by HPLC, which showed that the primary hydrolysis produced 28.1% oligosaccharides and 26.3% Hexoses. For the secondary hydrolysis in subcritical reactions, the highest yield of Hexoses, obtained at 280 °C and 44 s, was 39.5%. At lower temperatures, higher maximum yield of Hexoses was obtained, but the reaction times were longer. Kinetic analysis showed smaller reaction rate constants for Hexoses decomposition compared to those for oligosaccharide...
Zijuan Liu - One of the best experts on this subject based on the ideXlab platform.
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mammalian glucose permease glut1 facilitates transport of arsenic trioxide and methylarsonous acid
Biochemical and Biophysical Research Communications, 2006Co-Authors: Zijuan Liu, Eckhard Boles, Scott M Landfear, Marco A Sanchez, Xuan Jiang, Barry P. RosenAbstract:Arsenic exposure is associated with hypertension, diabetes, and cancer. Some mammals methylate arsenic. Saccharomyces cerevisiae hexose permeases catalyze As(OH)(3) uptake. Here, we report that mammalian glucose transporter GLUT1 catalyzes As(OH)(3) and CH(3)As(OH)(2) uptake in yeast or in Xenopus laevis oocytes. Expression of GLUT1 in a yeast lacking other glucose transporters allows for growth on glucose. Yeast expressing yeast HXT1 or rat GLUT1 transport As(OH)(3) and CH(3)As(OH)(2). The K(m) of GLUT1 is to 1.2mM for CH(3)As(OH)(2), compared to a K(m) of 3mM for glucose. Inhibition between glucose and CH(3)As(OH)(2) is noncompetitive, suggesting differences between the translocation pathways of Hexoses and arsenicals. Both human and rat GLUT1 catalyze uptake of both As(OH)(3) and CH(3)As(OH)(2) in oocytes. Thus GLUT1 may be a major pathway uptake of both inorganic and methylated arsenicals in erythrocytes or the epithelial cells of the blood-brain barrier, contributing to arsenic-related cardiovascular problems and neurotoxicity.
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arsenic trioxide uptake by hexose permeases in saccharomyces cerevisiae
Journal of Biological Chemistry, 2004Co-Authors: Zijuan Liu, Eckhard Boles, Barry P. RosenAbstract:Arsenic trioxide is a toxic metalloid and carcinogen that is also used as an anticancer drug, and for this reason it is important to identify the routes of arsenite uptake by cells. In this study the ability of hexose transporters to facilitate arsenic trioxide uptake in Saccharomyces cerevisiae was examined. In the absence of glucose, strains with disruption of the arsenite efflux gene ACR3 accumulated high levels of (73)As(OH)(3). The addition of glucose inhibited uptake by approximately 80%. Disruption of FPS1, the aquaglyceroporin gene, reduced glucose-independent uptake by only about 25%, and the residual uptake was nearly completely inhibited by Hexoses, including glucose, galactose, mannose, and fructose but not pentoses or disaccharides. A strain lacking FPS1, ACR3, and all genes for hexose permeases except for HXT3, HXT6, HXT7, and GAL2 exhibited hexose-inhibitable (73)As(OH)(3) uptake, whereas a strain lacking all 18 hexose transport-related genes (HXT1 to HXT17 and GAL2), FPS1 and ACR3, exhibited <10% of wild type (73)As(OH)(3) transport. When HXT1, HXT3, HXT4, HXT5, HXT7, or HXT9 was individually expressed in that strain, hexose-inhibitable (73)As(OH)(3) uptake was restored. In addition, the transport of [(14)C]glucose was inhibited by As(OH)(3). These results clearly demonstrate that hexose permeases catalyze the majority of the transport of the trivalent metalloid arsenic trioxide.