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  • 1
    Electronic Resource
    Electronic Resource
    Neutral invertase is a novel type of sucrose-cleaving enzyme (1999)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 107 (1999), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Metabolism of sucrose, a mobile source of energy and carbon, is an absolute requirement for the survival of heterotrophic plant organs. In these organs, different isoforms of invertase with discrete subcellular locations hydrolyze the disaccharide into hexoses and, thereby, feed sucrose into various biochemical pathways. In contrast to the invertases with acidic pH optima and a vacuolar or extracellular location, knowledge about the molecular nature of the cytoplasmic invertases (neutral and alkaline invertases) is still in its infancy. Here we report the cDNA cloning of a neutral invertase from carrot based on a partial peptide sequence from the purified enzyme. The function of the encoded polypeptide was confirmed by expression of the cDNA in Escherichia coli. The recombinant protein cleaved sucrose into glucose and fructose with the highest activity between pH 6.5 and 7.0. Unlike acid invertase, neutral invertase does not have the characteristics of a typical plant β-fructofuranosidase and sucrose akppears to be its sole substrate. The deduced amino acid sequence shares no similarity with sequences of acid invertases. The polypeptide is cysteine-rich and homologous sequences were only detected in the genomes of plants and photosynthetic bacteria. Hence, this protein must have evolved independently of other sucrose-cleaving enzymes. Transcripts for neutral invertase were found in all organs at different stages of development with slightly higher levels in developing organs, suggesting a more general and possibly a growth-related function of the enzyme in carrot sucrose metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1999.100202.x
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  • 2
    Electronic Resource
    Electronic Resource
    Structure, biosynthesis, and function of asparagine-linked glycans on plant glycoproteins (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 75 (1989), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In plants, glycoproteins with asparagine-linked glycans (oligosaccharides) are found in vacuoles, in the extracellular space or matrix, and associated with the endo-membrane system (endoplasmic reticulum, Golgi apparatus, plasma membrane, tonoplast). These glycans are of the high-mannose type, with a structure identical to that found in other organisms (mammals, yeast), or of the complex type with a β1–2 linked xylosyl residue not found in mammalian complex glycans. Asparagine-linked glycans play multiple roles by modifying the physicochemical properties of the polypeptides to which they are attached.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1989.tb06187.x
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  • 3
    Electronic Resource
    Electronic Resource
    Transport and posttranslational processing of the vacuolar enzyme α-mannosidase in jack-bean cotyledons (1988)
    Springer
    Planta 174 (1988), S. 271-282 
    Details
    ISSN: 1432-2048
    Keywords: Canavalia ; Cotyledon ; Endoplasmic reticulum ; α-Mannosidase (synthesis, processing) ; Protein body ; Protein processing ; Vacuole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract α-Mannosidase (EC 3.2.1.24) is a vacuolar enzyme which occurs abundantly in the cotyledons of the jack-bean (Canavalia ensiformis (L.) DC). The mature enzyme is a tetramer with two polypeptides each of relative molecular mass (Mr) 66000 and Mr 44000. The enzyme has an interesting molecular structure because in its native form, it does not bind to concanavalin A (ConA) in spite of the presence of a high-mannose glycan. α-Mannosidase is synthesized in the developing cotyledons of jack-beans at the same time as the abundant proteins canavalin and ConA. The enzyme is synthesized as a precursor which has an Mr of 110000 and is associated with the endoplasmic reticulum (ER). Antibodies against the deglycosylated subunits cross-react with the Mr-110000 precursor. Processing of the precursor to the constituent polypeptides occurs posttranslationally, probably in the protein bodies. Immunocytochemical evidence shows that α-mannosidase is present in the ER and the Golgi complex of developing cells, and accumulates in the protein bodies. Labeling with [3H]glucosamine shows that after processing only the Mr-66000 polypeptide has glucosamine-containing glycans. The synthesis of these glycans is inhibited by tunicamycin, indicating that they are asparagine-linked oligosaccharides. Analysis of the glycans shows that there is a large glycan that is retained by ConA and a small glycan that is not retained by ConA. The large glycan is only partially sensitive to α-mannosidase because of the presence of a terminal glucose residue. Cross-reaction of the large subunit with an antiserum directed against small, complex glycans of plant glycoproteins indicates that this polypeptide probably has a xylose-containing glycan. Pulse-chase experiments carried out in the presence of tunicamycin show that the presence of glycans is not required for transport of α-mannosidase out of the ER-Golgi system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394781
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  • 4
    Electronic Resource
    Electronic Resource
    Targeting and glycosylation of patatin the major potato tuber protein in leaves of transgenic tobacco (1989)
    Springer
    Planta 179 (1989), S. 171-180 
    Details
    ISSN: 1432-2048
    Keywords: Glycoprotein ; Nicotiana (transgenic) ; Patatin ; Protein targeting ; Tuber (protein) ; Vacuole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Patatin, the most abundant protein in the storage parenchyma cells of potato (Solanum tuberosum L.) tubers, is a vacuolar glycoprotein that consists of a number of closely related polypeptides and is encoded by a large gene family. To analyse the glycosylation pattern and the nature of the glycans on a single patatin polypeptide in a heterologous tissue we introduced a single chimaeric patatin gene into tobacco (Nicotiana tabacum L.) and studied its product in leaves. Patatin isolated from the leaves of transgenic tobacco plants is glycosylated at asparagine (Asn)60, and Asn90, but the third glycosylation site (Asn202) has no glycan. The two glycans are typical small complex glycans with xylose, fucose, mannose and N-acetylglucosamine in a ratio 1:1:3:2, the same ratio as found on patatin isolated from potato tubers. Expression of patatin in tobacco leaves was accompanied by the correct processing of the signal peptide, and the proper targeting of the glyco-protein to the vacuoles of mesophyll cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393687
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  • 5
    Electronic Resource
    Electronic Resource
    Development- and organ-specific expression of the genes for sucrose synthase and three isoenzymes of acid β-fructofuranosidase in carrot (1995)
    Springer
    Planta 195 (1995), S. 601-610 
    Details
    ISSN: 1432-2048
    Keywords: Daucus ; Gene expression ; β-Fructofuranosidase ; Invertase ; Sucrose partitioning ; Sucrose synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The steady-state levels of transcripts for cellwall β-fructofuranosidase (cwβF), for isoenzymes I and II of soluble acid β-fructofuranosidase (sI, sII), and for sucrose synthase (ss) were determined in the sink and source organs of developing carrot (Daucus carota L.) plants. The expression patterns of the four genes clearly differed. The expression of the gene for cwβF was development-specific but not organ-specific; high transcript levels were only found in plants with primary roots, with about equal amounts in leaf lamina, petioles and roots. The genes for sI and sII were mainly expressed in roots, sI predominating in primary roots and sII in developing tap roots. Transcripts for ss were found at a low level in all developing plant organs and were markedly up-regulated during the development of young leaves and during the transition of primary roots to tap roots. Developing tap roots contained only transcripts for sII and for ss. Marked alterations in the expression of these two genes after manipulation of the source/sink balance of these plants indicates their importance in sucrose partitioning. We suggest that ss regulates sucrose utilization in developing tap roots, whereas sII located in the vacuole controls sucrose storage and sugar composition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195721
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  • 6
    Electronic Resource
    Electronic Resource
    Structural organization and differential expression of carrot β-fructofuranosidase genes: identification of a gene coding for a flower bud-specific isozyme (1995)
    Springer
    Plant molecular biology 28 (1995), S. 189-194 
    Details
    ISSN: 1573-5028
    Keywords: β-fructofuranosidase ; invertase ; gene expression ; gene structure ; flower buds ; Daucus carota
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three genomic clones (Inv *Dc1, Inv *Dc2 and Inv *Dc3) were isolated by using the cDNA for carrot cell wall β-fructofuranosidase as a probe. The expression patterns of the three genes differed markedly. High levels of Inv *Dc1 transcripts were found in leaves and roots of young carrot, whereas in plants with developing tap roots no transcripts were detected. A high level of mRNA of Inv *Dc1 was also present in suspension-cultured cells. In developing reproductive organs, only low levels of transcripts of Inv *Dc1 were found in flower buds and flowers and none at later stages of development. In contrast, Inv *Dc2 and Inv *Dc3 were not expressed in vegetative plant organs. Invb1 *Dc1 was exclusively and strongly expressed in flower buds, and Inv *Dc3 at a very low level in suspension-cultured cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00042049
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  • 7
    Electronic Resource
    Electronic Resource
    Correct glycosylation, Golgi-processing, and targeting to protein bodies of the vacuolar protein phytohemagglutinin in transgenic tobacco (1988)
    Springer
    Planta 175 (1988), S. 170-183 
    Details
    ISSN: 1432-2048
    Keywords: Golgi apparatus ; Nicotiana (transgenic) ; Phaseolus (phytohemagglutinin) ; Phytohemagglutinin ; Protein bodies ; Protein targeting ; Transformation (tobacco)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We used a heterologous system (transgenic Nicotiana tabacum L.) to investigate the processing, assembly and targeting of phytohemagglutinin (PHA), the lectin of the common bean, Phaseolus vulgaris L. In the bean, this glycoprotein accumulates in the protein bodies of the storage parenchyma cells in the cotyledons, and each polypeptide has a high-mannose glycan attached to Asn12 and a complex glycan on Asn60. The gene for PHA-L, dlec2, with 1200 basepairs (bp) 5′ upstream and 1600 bp 3′ downstream from the coding sequence was introduced into tobacco using Agrobacterium-mediated transformation (T. Voelker et al., 1987, EMBO J. 6, 3571–3577). Examination of thin sections of tobacco seeds by immunocytochemistry with antibodies against PHA showed that PHA-L accumulated in the amorphous matrix of the protein bodies in the embryo and endosperm. This localization was confirmed using a non-aqueous method to isolate the protein bodies from mature tobacco seeds. The biochemical analysis of tobacco PHA indicated that the signal peptide had been correctly removed, and that the polypeptides formed 6.4 S oligomers; tobacco PHA had a high-mannose glycan at Asn12 and a complex glycan at Asn60. The presence of the complex glycan shows that transport to the protein bodies was mediated by the Golgi complex. At seed maturity, a substantial portion of the PHA-L remained associated with the endoplasmic reticulum and the Golgi complex, as indicated by fractionation experiments using aqueous media and the presence of two high-mannose glycans on some of the polypeptides. Taken together, these data show that insertion of the nascent PHA into the endoplasmic reticulum, signal peptide processing, glycosylation, assembly into oligomers, glycan modification in the Golgi, and targeting of the protein occur faithfully in this heterologous system, although transport may not be as efficient as in bean cotyledons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392425
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  • 8
    Electronic Resource
    Electronic Resource
    cDNA cloning of an extracellular dermal glycoprotein of carrot and its expression in response to wounding (1992)
    Springer
    Planta 188 (1992), S. 432-438 
    Details
    ISSN: 1432-2048
    Keywords: Daucus (glycoprotein) ; Defense ; Epidermis (glycoprotein) ; Glycoprotein (extracellular) ; Wound response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Suspension-cultured cells of carrot (Daucus carota L.) synthesize and secrete a glycoprotein that is normally found only in dermal tissues (epidermis, endodermis and periderm). This protein, previously called GP57, is now referred to as EDGP (E xtracellular D ermal G lyco P rotein). We purified sufficient quantities of EDGP to obtain amino-acid sequences on two internal tryptic peptides and screened a cDNA library of young carrot roots with antiserum to EDGP and with oligonucleotides corresponding to the peptides. Here we report the derived amino-acid sequence of EDGP. Sequence comparisons show that it has 40% amino-acid sequence identity with 7S basic globulin, a protein that is released when soybean seeds are soaked in hot water for a few hours. We suggest that these two proteins belong to a new family of dermal proteins. As far as we know, this is the first reported derived amino-acid sequence for protein that is specific to the epidermis and other dermal tissues. The level of EDGP mRNA is low in dry seeds, but increases rapidly in growing seedlings as they develop dermal tissues. The level of mRNA is low in storage roots, but increases rapidly in response to wounding. The presence of EDGP in dermal tissues and its up-regulation in response to wounding indicate a role in the response of plants to biotic and-or abiotic stresses. An unusual feature of the amino-acid sequence of EDGP is that it contains a short motif, which is present at the active site of aspartyl proteases such as pepsin and chymosin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192811
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  • 9
    Electronic Resource
    Electronic Resource
    Transformation and regeneration of carrot (Daucus carota L.) (1998)
    Springer
    Molecular breeding 4 (1998), S. 119-127 
    Details
    ISSN: 1572-9788
    Keywords: Daucus carota ; Agrobacterium tumefaciens ; genetic transformation ; β-glucuronidase ; 35S promoter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A protocol is presented for the efficient transformation of carrot (Daucus carota L. cv. Nantaise) by Agrobacterium tumefaciens. The binary vector contained the marker gene β-glucuronidase (GUS), driven by the 35S promoter of cauliflower mosaic virus, and the nptII gene, which confers kanamycin resistance. Highest T-DNA transfer rates were obtained by co-cultivating bacteria with hypocotyl segments of dark-grown seedlings on solidified B5 medium containing naphthaleneacetic acid and 6-benzylaminopurine. After 2 days, bacterial growth was stopped with antibiotics. Two weeks later, the explants were placed on agar containing the kanamycin derivate geneticin; antibiotic-resistant calli developed during the following 4 weeks. Suspension cultures were obtained from resistant calli and plants regenerated via somatic embryogenesis in liquid culture. The majority of plants were phenotypically normal and, depending on the Agrobacterium strain used, harbored single or multiple copies of the T-DNA. About equal levels of GUS activity were found in different organs of young plants up to 6 weeks after embryogenesis. In leaves of older plants, GUS activity was markedly reduced, whereas the activities in phloem and xylem parenchyma cells of developing tap roots were still high and fairly uniform. Thus, the 35S promoter may be a useful tool to drive the expression of transgenes in developing carrot storage roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009681725540
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  • 10
    Electronic Resource
    Electronic Resource
    Tissue-specific expression of two genes for sucrose synthase in carrot (Daucus carota L.) (1999)
    Springer
    Plant molecular biology 39 (1999), S. 349-360 
    Details
    ISSN: 1573-5028
    Keywords: sucrose synthase ; Daucus carota ; sucrose partitioning ; starch accumulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sucrose synthase, which cleaves sucrose in the presence of uridine diphosphate (UDP) into UDP-glucose and fructose, is thought to be a key determinant of sink strength of heterotrophic plant organs. To determine the roles of the enzyme in carrot, we characterized carrot sucrose synthase at the molecular level. Two genes (Susy*Dc1 and Susy*Dc2) were isolated. The deduced amino acid sequences are 87% identical. However, the sequences upstream of the translation initiation codons are markedly different, as are the expression patterns of the two genes. Susy*Dc2 was exclusively expressed in flowers. Transcripts for Susy*Dc1 were found in stems, in roots at different developmental stages, and in flower buds, flowers and maturing seeds, with the highest levels in strong utilization sinks for sucrose such as growing stems and tap root tips. Expression of Susy*Dc1 was regulated by anaerobiosis but not by sugars or acetate. The carrot sucrose synthase protein is partly membrane-associated and this insoluble form may be directly involved in cellulose biosynthesis. Tap roots of the carrot cultivar used accumulated starch in the vicinity of the vascular bundles, which correlated with high sucrose synthase transcript levels. This finding suggests that soluble sucrose synthase in tap roots channels sucrose towards starch biosynthesis. Starch accumulation appears to be transient and may be involved in sucrose partitioning to developing tap roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006199003756
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