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Query: EC:3.2.1.26 (invertase)
 4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Plants possess two alternative biochemical pathways for sucrose (Suc) degradation. One involves hydrolysis by invertase followed by phosphorylation via hexokinase and fructokinase, and the other route-which is unique to plants-involves a UDP-dependent cleavage of Suc that is catalyzed by Suc synthase (SuSy). In the present work, we tested directly whether a bypass of the endogenous SuSy route by ectopic overexpression of invertase or Suc phosphorylase affects internal oxygen levels in growing tubers and whether this is responsible for their decreased starch content. (a) Oxygen tensions were lower within transgenic tubers than in wild-type tubers. Oxygen tensions decreased within the first 10 mm of tuber tissue, and this gradient was steeper in transgenic tubers. (b) Invertase-overexpressing tubers had higher activities of glyceraldehyde-3-phosphate dehydrogenase, lactate dehydrogenase, and alcohol dehydrogenase, and (c) higher levels of lactate. (d) Expression of a low-oxygen-sensitive Adh1-beta-glucuronidase reporter gene construct was more strongly induced in the invertase-overexpressing background compared with wild-type background. (e) Intact transgenic tubers had lower ATP to ADP ratios than the wild type. ATP to ADP ratio was restored to wild type, when discs of transgenic tubers were incubated at 21% (v/v) oxygen. (f) Starch decreased from the periphery to the center of the tuber. This decrease was much steeper in the transgenic lines, leading to lower starch content especially near the center of the tuber. (g) Metabolic fluxes (based on redistribution of (14)C-glucose) and ATP to ADP ratios were analyzed in more detail, comparing discs incubated at various external oxygen tensions (0%, 1%, 4%, 8%, 12%, and 21% [v/v]) with intact tubers. Discs of Suc phosphorylase-expressing lines had similar ATP to ADP ratios and made starch as fast as wild type in high oxygen but had lower ATP to ADP ratios and lower rates of starch synthesis than wild type at low-oxygen tensions typical to those found inside an intact tuber. (h) In discs of wild-type tubers, subambient oxygen concentrations led to a selective increase in the mRNA levels of specific SuSy genes, whereas the mRNA levels of genes encoding vacuolar and apoplastic invertases decreased. (i) These results imply that repression of invertase and mobilization of Suc via the energetically less costly route provided by SuSy is important in growing tubers because it conserves oxygen and allows higher internal oxygen tensions to be maintained than would otherwise be possible.
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PMID:A bypass of sucrose synthase leads to low internal oxygen and impaired metabolic performance in growing potato tubers. 1291 61

Extracellular invertases are suggested to play a crucial role in the arbuscular mycorrhiza (AM) symbiosis to fulfil the increased sink function of the mycorrhizal root and the supply of the obligate biotrophic AM fungus with hexoses. In tomato (Lycopersicon esculentum), LIN6 represents an apoplastic invertase which is described as a key enzyme in establishing and maintaining sink metabolism. In this study, transcript levels of LIN6 were analysed in tomato roots colonized with the AM fungus Glomus intraradices. Using real-time RT-PCR, a nearly 3-fold increase in LIN6 mRNA levels was detected at late stages of mycorrhization (11 weeks after inoculation). A 1.8-fold induction could already be achieved at earlier stages (5 weeks after inoculation) using higher inoculum concentrations, whereas wounding of non-mycorrhizal roots resulted in up to 12-fold enhanced LIN6 transcripts. As revealed by in situ hybridization, the expression of LIN6 upon mycorrhization was specifically restricted to colonized cells and to the central cylinder. Such a strongly localized pattern due to mycorrhizal cells and to the central core could also be shown for promoter activity using transgenic Nicotiana tabacum plants expressing the gene coding for beta-glucuronidase under the control of the LIN6 promoter. The moderate induction of LIN6 expression in mycorrhizal tomato roots compared with stress-stimulated induction suggested a fine-tuning in the activation of sink metabolism in the mutualistic interaction, avoiding stress-induced defence reactions.
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PMID:Arbuscular mycorrhiza induces gene expression of the apoplastic invertase LIN6 in tomato (Lycopersicon esculentum) roots. 1705 Jun 39

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) alcc::wINV 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 beta-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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PMID:Regulation of arbuscular mycorrhization by carbon. The symbiotic interaction cannot be improved by increased carbon availability accomplished by root-specifically enhanced invertase activity. 1741 41

In a four-week experiment on 60 7-day-old BUT-9 male turkeys the effects of dietary fructooligosaccharides (pure nystose and a fructooligosaccharide mixture) supplemented at 1 and 2%, were studied on ileal and caecal metabolism. The control carbohydrate was cellulose, added also at 1 or 2%. Each dietary treatment consists of 10 birds kept individually. The average degree of polymerisation of the nystose and oligofructose preparation amounted to 2.9 and 4.1, respectively. The addition of nystose significantly decreased the pH value and viscosity in the ileal contents compared with the cellulose treatment. On the other hand, the oligofructose preparation increased the activity of sucrase and lactase in the ileal mucosal by 30-60% and 33-47%, respectively. Both fructan preparations similarly acidified the caecal and colonic digesta (by 0.2-0.4 pH units) as well as diminished the activity of bacterial harmful beta-glucuronidase (by 24-40%), but only nystose caused an enlargement of the caeca and effectively reduced caecal ammonia concentration, especially at a higher dose. Oligofructose supplementation at 2% caused a 3.5-fold increase of bacterial activity of alph- and beta-galactosidase, while 2% nystose resulted in 1.7 and 3 times higher alpha- and beta-glucosidases activities, respectively. Compared to oligofructose, dietary nystose increased propionic and decreased butyric fermentation in caeca. Nystose and oligofructose preparations added at 2% reduced the triacylglycerol concentration in the serum in comparison to the addition of 2% cellulose by 46 and 25%, respectively. Beside the fact that dietary levels of supplementation were of great importance, the results indicated that even small difference in the length of carbohydrate chain may cause different physiological responses.
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PMID:Gastrointestinal tract metabolism of young turkeys fed diets supplemented with pure nystose or a fructooligosaccharide mixture. 1894 86

To elucidate the regulation pattern of extracellular invertase LIN6 of tomato, the corresponding promoter has been cloned and the sink-tissue specific expression and its regulation by sugars, stress stimuli, growth regulators, and the diurnal rhythm is shown. The in situ analysis of transgenic tobacco plants expressing a LIN6 promoter::beta-glucuronidase reporter gene fusion demonstrates LIN6 expression in sink tissues, such as pollen grains and vascular tissues of leaves and stems. LIN6 is up-regulated in close proximity to wounded tissue, and by methyl jasmonate and abscisic acid, global signals known to modulate defence/stress response. Salicylic acid on the other hand, as well as acetyl salicylic acid, suppresses LIN6 expression, supporting the fact that LIN6 is an inducible compound of the defence/stress response pathway that is antagonistically regulated by jasmonates and salicylates. Induction of the LIN6 promoter in stable transformed BY2 suspension cultures by sucrose and the growth-promoting phytohormones cytokinin and auxin along histochemical expression data, showing LIN6 expression in germinating seeds and seedlings, indicates a role of LIN6 invertase during growth processes. In addition, LIN6 is regulated by a diurnal rhythm that drives LIN6 expression in subjective dawn. Transactivation assays with circadian oscillator elements of Arabidopsis Circadian Clock Associated 1 and Late Elongated Hypocotyl demonstrate functional interaction with the LIN6 promoter.
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PMID:Extracellular invertase LIN6 of tomato: a pivotal enzyme for integration of metabolic, hormonal, and stress signals is regulated by a diurnal rhythm. 1929 49

An experiment was conducted to investigate the effects of diets containing soybean meal (SBM), soybean protein concentrate (SPC), and soybean protein isolate (SPI) on growth performance and gut function of the young turkey. A total of 812 one-day-old male turkey poults were randomly assigned to 4 dietary treatments, with 7 pens per treatment and 29 birds per pen. The 4 experimental diets contained SBM, SBM-SPC, SPC, and SPI and were fed throughout the two 4-wk experimental periods. In each period, the diets were isonitrogenous and isocaloric and contained similar amounts of total and water-soluble nonstarch polysaccharides. The content of oligosaccharides differed among the diets and averaged 2.4, 1.9, 0.9, and 0.1% for SBM, SBM-SPC, SPC, and SPI, respectively. When compared with SBM, birds consuming the SBM-SPC and SPC diets had higher (P<0.05) final BW (4.32 vs. 4.45 and 4.46 kg, respectively). Incorporation of SPI as a substitute for SBM resulted in improved (P<0.05) feed utilization (from 1.76 to 1.67) but did not affect the final BW. Significant changes in cecal concentrations of short-chain fatty acids were observed and averaged 130, 103, and 89 micromol/g of digesta for the SBM, SBM-SPC, and SPC diets, respectively. This coincided with the proportional decrease in dietary oligosaccharide content (from 2.4 to 0.9%) and was further substantiated by a significant decrease in ileum weights. Feeding the SPI diet resulted in the lowest ileal and cecal tissue weights as well as the lowest cecal short-chain fatty acids concentration. There was no effect of diet on digesta pH, viscosity, and mucosal sucrase and maltase activities. Bacterial beta-glucuronidase activity was decreased (P=0.08) in the cecum (from 0.98 to 0.60 U/g) with decreased dietary oligosaccharide content. In conclusion, partial or almost complete substitution of SBM with SPC suppressed the fermentation processes in the ceca but enhanced the growth rate. Substitution of SBM with SPI significantly improved feed utilization but decreased BW of 4-wk-old turkeys with no effect on growth rate of older 8-wk-old birds.
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PMID:The effect of diets containing soybean meal, soybean protein concentrate, and soybean protein isolate of different oligosaccharide content on growth performance and gut function of young turkeys. 1976 67

Sugars play indispensable roles in biological reactions and are distributed into various tissues or organelles via transporters in plants. Under abiotic stress conditions, plants accumulate sugars as a means to increase stress tolerance. Here, we report an abiotic stress-inducible transporter for monosaccharides from Arabidopsis thaliana that is termed ESL1 (ERD six-like 1). Expression of ESL1 was induced under drought and high salinity conditions and with exogenous application of abscisic acid. Promoter analyses using beta-glucuronidase and green fluorescent protein reporters revealed that ESL1 is mainly expressed in pericycle and xylem parenchyma cells. The fluorescence of ESL1-green fluorescent protein-fused protein was detected at tonoplast in transgenic Arabidopsis plants and tobacco BY-2 cells. Furthermore, alanine-scanning mutagenesis revealed that an N-terminal LXXXLL motif in ESL1 was essential for its localization at the tonoplast. Transgenic BY-2 cells expressing mutated ESL1, which was localized at the plasma membrane, showed an uptake ability for monosaccharides. Moreover, the value of K(m) for glucose uptake activity of mutated ESL1 in the transgenic BY-2 cells was extraordinarily high, and the transport activity was independent from a proton gradient. These results indicate that ESL1 is a low affinity facilitated diffusion transporter. Finally, we detected that vacuolar invertase activity was increased under abiotic stress conditions, and the expression patterns of vacuolar invertase genes were similar to that of ESL1. Under abiotic stress conditions, ESL1 might function coordinately with the vacuolar invertase to regulate osmotic pressure by affecting the accumulation of sugar in plant cells.
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PMID:Functional analysis of an Arabidopsis thaliana abiotic stress-inducible facilitated diffusion transporter for monosaccharides. 1990 Oct 34

The practical use of RNA-mediated approaches including antisense RNA, ribozymes and siRNAs for specific inhibition of gene expression is limited by lack of simple quantitative methods to rapidly test efficacy in vivo. There have been indications that cotransfer of target::reporter gene fusions with constructs designed against the target sequence, followed by quantification of transient reporter gene activity might be effective. Here, we report detailed testing of the approach in plants, using diverse target::luciferase fusions and antisense or ribozyme constructs. We used quantitative transient luciferase activity (Luc) assays to test antisense constructs against beta-glucuronidase, PR glucanase, vacuolar invertase and cucumber mosaic virus, as well as ribozymes against watermelon mosaic virus and tobacco anionic peroxidase. For constructs previously tested in transgenic plants, the results correspond well with those from the transient expression assay. Target susceptibility was generally not strongly influenced by luciferase fusion, and the assay was not highly dependent on target sequence length. Some sequences reduced Luc activity below the level for reliable quantification, but suitable alternative fusions were readily produced. Transcriptional and translation fusions were effective for 5' target::luc constructs. Translational fusions were more reliable for luc::target 3' constructs. With minimal preliminary work to prepare suitable target::luciferase fusions, the approach appears generally applicable for rapid in vivo validation of effectiveness and specificity of constructs designed for RNA-mediated down-regulation of plant genes.
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PMID:Evaluation and application of a luciferase fusion system for rapid in vivo analysis of RNAi targets and constructs in plants. 2010 31

Biotrophic fungal and oomycete pathogens alter carbohydrate metabolism in infected host tissues. Symptoms such as elevated soluble carbohydrate concentrations and increased invertase activity suggest that a pathogen-induced carbohydrate sink is established. To identify pathogen-induced regulators of carbohydrate sink strength, quantitative real-time polymerase chain reaction was used to measure transcript levels of invertase and hexose transporter genes in biotrophic pathogen-infected grapevine (Vitis vinifera) leaves. The hexose transporter VvHT5 was highly induced in coordination with the cell wall invertase gene VvcwINV by powdery and downy mildew infection. However, similar responses were also observed in response to wounding, suggesting that this is a generalized response to stress. Analysis of the VvHT5 promoter region indicated the presence of multiple abscisic acid (ABA) response elements, suggesting a role for ABA in the transition from source to sink under stress conditions. ABA treatment of grape leaves was found to reproduce the same gene-specific transcriptional changes as observed under biotic and abiotic stress conditions. Furthermore, the key regulatory ABA biosynthetic gene, VvNCED1, was activated under these same stress conditions. VvHT5 promoter::beta-glucuronidase-directed expression in transgenic Arabidopsis (Arabidopsis thaliana) was activated by infection with powdery mildew and by ABA treatment, and the expression was closely associated with vascular tissue adjacent to infected regions. Unlike VvHT1 and VvHT3, which appear to be predominantly involved in hexose transport in developing leaves and berries, VvHT5 appears to have a specific role in enhancing sink strength under stress conditions, and this is controlled through ABA. Our data suggest a central role for ABA in the regulation of VvcwINV and VvHT5 expression during the transition from source to sink in response to infection by biotrophic pathogens.
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PMID:Involvement of abscisic acid in the coordinated regulation of a stress-inducible hexose transporter (VvHT5) and a cell wall invertase in grapevine in response to biotrophic fungal infection. 2034 11


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