Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.31 (beta-glucuronidase)
 7,680 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

ADP-glucose pyrophosphorylase (AGP) catalyzes a key regulatory step in starch synthesis. To elucidate the molecular basis for the expression of the potato (Solanum tuberosum L.) AGP during tuber development, the structure of the small subunit AGP (sAGP) gene and its patterns of expression were examined. DNA sequence analysis revealed that the sAGP gene is over 5.5 kilobases long and has a complex structure including eight introns. Unlike the situation in other plants where tissue-specific sAGP are found, our Southern and Northern blot analysis indicated that the same sAGP gene is expressed both in tubers (non-photosynthetic tissue) and leaves (photosynthetic tissue). These data were supported by comparing sequences of isolated sAGP leaf cDNAs to the tuber cDNA sequence, by primer extension analysis of leaf and tuber poly(A)+ RNAs, and by the spatial expression patterns of a gusA (beta-glucuronidase) reporter gene driven by the potato sAGP promoter in transgenic potato plants. Although the sAGP gene appeared to be transcriptionally controlled in both developing tubers and in leaves, the relative level of leaf antigen was significantly lower than its level of transcript, indicating that sAGP expression in leaves is primarily regulated post-transcriptionally. The observed tissue type-dependent regulation of sAGP expression appears to control the extent of starch biosynthesis by regulating the levels of this enzyme and, thus, alleviate the need for tissue-specific forms of the sAGP in potato.
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PMID:Structure and expression of the potato ADP-glucose pyrophosphorylase small subunit. 798 10

ADP-glucose pyrophosphorylase (AGPase) is a key regulatory enzyme in starch biosynthesis in higher plants. A 3.2-kb promoter of the large subunit gene of the AGPase from potato has been isolated and its activity analyzed in transgenic potato and tobacco plants using a promoter-beta-glucuronidase fusion system. The promoter was active in various starch-containing cells, including guard cells, tuber parenchyma cells, and the starch sheath layer of stems and petioles. No expression was observed in mesophyll cells. Analysis of various promoter derivatives showed that with respect to expression in petioles and stems, essential elements must be located in the 5' distal region of the promoter, whereas elements important for expression in tuber parenchyma cells are located in an internal fragment comprising nucleotides from positions -500 to -1200. Finally, a 0.3-kb 5' proximal promoter fragment was identified that was sufficient to obtain exclusive expression in guard cells of transgenic potato and tobacco plants. The implications of our observations are discussed with respect to starch synthesis in various tissues and the use of the newly identified promoter as a tool for stomatal biology.
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PMID:A truncated version of an ADP-glucose pyrophosphorylase promoter from potato specifies guard cell-selective expression in transgenic plants. 803 1

ADP-glucose pyrophosphorylase (AGP) is a key regulatory enzyme in the biosynthesis of starch in higher plants. Previous studies have suggested that, unlike other plants that display tissue-specific AGP genes, potato expresses the same AGP small-subunit gene (sAGP) in multiple tissues. This view was confirmed by the spatial patterns of expression of the sAGP gene in transgenic potato plants observed when a promoter-dependent-beta-glucuronidase (beta-GUS) system was used. sAGP-beta-GUS chimeric gene fusions were expressed at high levels in tubers and in many other starch-containing cells throughout the plant. Deletional analysis of the 5'-upstream region of sAGP revealed that the observed spatial patterns of expression were due to different regions of the promoter of sAGP functioning in combination to confer cell- and organ-specific patterns of expression. Depending on the tissue examined, the patterns of reporter-gene expression were enhanced, suppressed, or altered when the 3'-nopaline-synthase terminator was replaced by the 3'-flanking sequence of sAGP. The observed cellular expression patterns of sAGP only partially overlap with the reported expression patterns of the major large-subunit gene (lAGP) in leaves. Since AGP is a heterotetrameric enzyme, composed of two sAGP and two lAGP subunits, this difference in the cellular expression patterns as well as quantitative differences in expression of the two AGP genes may account for the observed post-transcriptional regulation, i.e., relatively high levels of transcript but low levels of sAGP subunit in leaves.
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PMID:Cis-elements important for the expression of the ADP-glucose pyrophosphorylase small-subunit are located both upstream and downstream from its structural gene. 867 61

The aim of the work described in this paper was to characterize the tubers of potato (Solanum tuberosum var. Prairie) plants that had been transformed with the Escherichia coli ADPglucose pyrophosphorylase (EC 2.7.7.27) gene, glgC-16, under the control of a patatin promoter. Over 30 lines of transformed plants with increased ADPglucose pyrophosphorylase activity were obtained. The tubers of six of these lines were compared with those of control plants expressing the gene for beta-glucuronidase. The average increase in pyrophosphorylase activity was 200%, and the highest was 400%. Western immunoblotting of tuber extracts showed that the amounts of glgC-16 protein were linearly related to the extractable activity of the ADPglucose pyrophosphorylase. Cell fractionation studies showed that the increased activity of the pyrophosphorylase in the glgC-16 tubers had a similar intracellular location, the amyloplast fraction, to that found in the control tubers. No pleiotropic changes in the maximum catalytic activities of the following enzymes could be detected in the glgC-16 tubers: sucrose synthase, fructokinase, UDPglucose pyrophosphorylase, phosphofructokinase, soluble starch synthase, starch branching enzyme, phosphoglucomutase and alkaline inorganic pyrophosphatase. The glgC-16 tubers are held to be suitable for the study of the role of ADPglucose pyrophosphorylase in the control of starch synthesis.
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PMID:Characterization of transgenic potato (Solanum tuberosum) tubers with increased ADPglucose pyrophosphorylase. 897 57

Transgenic plants of Arabidopsis thaliana Heynh., transformed with a bacterial beta-glucuronidase (GUS) gene under the control of the promoter of the small subunit (ApS) of ADP-glucose pyrophosphorylase (AGPase), exhibited GUS staining in leaves (including stomata), stems, roots and flowers. Cross-sections of stems revealed GUS staining in protoxylem parenchyma, primary phloem and cortex. In young roots, the staining was found in the root tips, including the root cap, and in vascular tissue, while the older root-hypocotyl axis showed prominent staining in the secondary phloem and paratracheary parenchyma of secondary xylem. The GUS staining co-localized with ApS protein, as found by tissue printing using antibodies against ApS. Starch was found only in cell and tissue types exhibiting GUS staining and ApS labelling, but not in all of them. For example, starch was lacking in the xylem parenchyma and secondary phloem of the root-hypocotyl axis. Sucrose potently activated ApS gene expression in leaves of wild-type (wt) plants, and in transgenic seedlings grown on sucrose medium where GUS activity was quantified with 4-methylumbelliferyl-beta-glucuronide as substrate. Okadaic acid, an inhibitor of protein phosphatases 1 and 2A, completely blocked expression of ApS in mature leaves of wt plants and prevented GUS staining in root tips and flowers of the transgenic plants, suggesting a similar signal transduction mechanism for ApS expression in various tissues. The data support the key role of AGPase in starch synthesis, but they also underlie the ubiquitous importance of the ApS gene for AGPase function in all organs/tissues of Arabidopsis.
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PMID:The small subunit ADP-glucose pyrophosphorylase ( ApS) promoter mediates okadaic acid-sensitive uidA expression in starch-synthesizing tissues and cells in Arabidopsis. 1278 26

A 1.8 kb 5'-flanking region of the large subunit of ADP-glucose pyrophosphorylase, isolated from watermelon (Citrullus vulgaris S.), has fruit-specific promoter activity in transgenic tomato plants. Two negative regulatory regions, from -986 to -959 and from -472 to -424, were identified in this promoter region by fine deletion analyses. Removal of both regions led to constitutive expression in epidermal cells. Gain-of-function experiments showed that these two regions were sufficient to inhibit RFP (red fluorescent protein) expression in transformed epidermal cells when fused to the cauliflower mosaic virus (CaMV) 35S minimal promoter. Gel mobility shift experiments demonstrated the presence of leaf nuclear factors that interact with these two elements. A TCCAAAA motif was identified in these two regions, as well as one in the reverse orientation, which was confirmed to be a novel specific cis-element. A quantitative beta-glucuronidase (GUS) activity assay of stable transgenic tomato plants showed that the activities of chimeric promoters harbouring only one of the two cis-elements, or both, were approximately 10-fold higher in fruits than in leaves. These data confirm that the TCCAAAA motif functions as a fruit-specific element by inhibiting gene expression in leaves.
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PMID:Two negative cis-regulatory regions involved in fruit-specific promoter activity from watermelon (Citrullus vulgaris S.). 1907 62

Molecular farming refers to the process of creating bioengineered plants with the capability of producing potentially valuable products, such as drugs, vaccines, and chemicals. We have investigated the potential of the sweet potato ADP-glucose pyrophosphorylase gene (ibAGP1) promoter and its transit peptide (TP) as an expression system for the mass production of foreign proteins in potato. The ibAGP1 promoter and its TP sequence were transformed into potato along with beta-glucuronidase (GUS) as a reporter gene, and GUS activity was subsequently analyzed in the transgenic potato plants. In tuber tissues, GUS activity in transgenic plants carrying only the ibAGP1 promoter (ibAGP1::GUS) increased up to 15.6-fold compared with that of transgenic plants carrying only the CaMV35S promoter (CaMV35S::GUS). GUS activity in transgenic plants was further enhanced by the addition of the sweetpotato TP to the recombinant vector (ibAGP1::TP::GUS), with tuber tissues showing a 26-fold increase in activity compared with that in the CaMV35S::GUS-transgenic lines. In leaf tissues, the levels of GUS activity found in ibAGP1::GUS-transgenic lines were similar to those in CaMV35S::GUS-lines, but they were significantly enhanced in ibAGP1::TP::GUS-lines. GUS activity gradually increased with increasing tuber diameter in ibAGP1::GUS-transgenic plants, reaching a maximum level when the tuber was 35 mm in diameter. In contrast, extremely elevated levels of GUS activity - up to about 10-fold higher than that found in CaMV35S::GUS-lines - were found in ibAGP1::TP::GUS-transgenic lines at a much earlier stage of tuber development (diameter 4 mm), and these higher levels were maintained throughout the entire tuber developmental stage. These results suggest that the sweetpotato ibAGP1 promoter and its TP are a potentially strong foreign gene expression system that can be used for molecular farming in potato plants.
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PMID:The sweet potato ADP-glucose pyrophosphorylase gene (ibAGP1) promoter confers high-level expression of the GUS reporter gene in the potato tuber. 1981 8