Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Functional characterization of NRAMP3 and NRAMP4 from the metal hyperaccumulator Thlaspi caerulescens
    Oomen, R.J.F.J. ; Wu, J. ; Lelievre, F. ; Blanchet, S. ; Richaud, P. ; Barbier-Brygoo, H. ; Aarts, M.G.M. ; Thomine, S. - \ 2009
    New Phytologist 181 (2009)3. - ISSN 0028-646X - p. 637 - 650.
    arabidopsis-thaliana - gene encodes - heavy-metal - transporter genes - iron transport - saccharomyces-cerevisiae - expression differences - zinc transporter - cadmium - protein
    The ability of metal hyperaccumulating plants to tolerate and accumulate heavy metals results from adaptations of metal homeostasis. NRAMP metal transporters were found to be highly expressed in some hyperaccumulating plant species. Here, we identified TcNRAMP3 and TcNRAMP4, the closest homologues to AtNRAMP3 and AtNRAMP4 in Thlaspi caerulescens and characterized them by expression analysis, confocal imaging and heterologous expression in yeast and Arabidopsis thaliana. TcNRAMP3 and TcNRAMP4 are expressed at higher levels than their A. thaliana homologues. When expressed in yeast TcNRAMP3 and TcNRAMP4 transport the same metals as their respective A. thaliana orthologues: iron (Fe), manganese (Mn) and cadmium (Cd) but not zinc (Zn) for NRAMP3; Fe, Mn, Cd and Zn for NRAMP4. They also localize at the vacuolar membrane in A. thaliana protoplasts. Inactivation of AtNRAMP3 and AtNRAMP4 in A. thaliana results in strong Cd and Zn hypersensitivity, which is fully rescued by TcNRAMP3 or TcNRAMP4 expression. However, metal tolerance conferred by TcNRAMP expression in nramp3nramp4 mutant does not exceed that of wild-type A. thaliana. Our data indicate that the difference between TcNRAMP3 and TcNRAMP4 and their A. thaliana orthologues does not lie in a different protein function, but probably resides in a different expression level or expression pattern
    The limited importance of size-asymmetric light competition and growth of pioneer species in early secondary forest succession in Vietnam
    Kuijk, Marijke van; Anten, N.P.R. ; Oomen, R.J. ; Bentum, D.W. van; Werger, M.J.A. - \ 2008
    Oecologia 157 (2008)1. - ISSN 0029-8549 - p. 1 - 12.
    Canopy model - Light capture - Photosynthesis - Regeneration - Tropical forest

    It is generally believed that asymmetric competition for light plays a predominant role in determining the course of succession by increasing size inequalities between plants. Size-related growth is the product of size-related light capture and light-use efficiency (LUE). We have used a canopy model to calculate light capture and photosynthetic rates of pioneer species in sequential vegetation stages of a young secondary forest stand. Growth of the same saplings was followed in time as succession proceeded. Photosynthetic rate per unit plant mass (P mass: mol C g-1 day-1), a proxy for plant growth, was calculated as the product of light capture efficiency [Φmass: mol photosynthetic photon flux density (PPFD) g-1 day-1] and LUE (mol C mol PPFD-1). Species showed different morphologies and photosynthetic characteristics, but their light-capturing and light-use efficiencies, and thus P mass, did not differ much. This was also observed in the field: plant growth was not size-asymmetric. The size hierarchy that was present from the very early beginning of succession remained for at least the first 5 years. We conclude, therefore, that in slow-growing regenerating vegetation stands, the importance of asymmetric competition for light and growth can be much less than is often assumed.

    In vivo expression of a Cicer arietinum B-galactosidase in potato tubers leads to a reduction of the Galactan side-chains in cell wall pectin
    Martin, I. ; Dopico, B. ; Munoz, F.J. ; Esteban, R. ; Oomen, R.J.F.J. ; Driouich, A. ; Vincken, J.P. ; Visser, R.G.F. ; Labrador, E. - \ 2005
    Plant and Cell Physiology 46 (2005)10. - ISSN 0032-0781 - p. 1613 - 1622.
    rhamnogalacturonan-i - infrared microspectroscopy - partial-purification - natural substrate - architecture - epicotyls - growth - elongation - autolysis - plants
    We report the generation of Solanum tuberosum transformants expressing Cicer arietinum ßIII-Gal. ßIII-Gal is a ß-galactosidase able to degrade cell wall pectins during cell wall loosening that occurs prior to cell elongation. cDNA corresponding to the gene encoding this protein was identified among several chickpea ß-galactosidase cDNAs, and named CanBGal-3. CanBGal-3 cDNA was expressed in potato under the control of the granule-bound starch synthase promoter. Three ßIII-Gal transformants with varying levels of expression were chosen for further analysis. The transgenic plants displayed no significant altered phenotype compared to the wild type. However, ß-galactanase and ß-galactosidase activities were increased in the transgenic tuber cell walls and this affected the potato tuber pectins. A reduction in the galactosyl content of up to 50% compared to the wild type was observed in the most extreme transformant, indicating a reduction of 1,4-ß-galactan side-chains, as revealed by analysis with LM5 specific antibodies. Our results confirm the notion that the pectin-degrading activity of chickpea ßIII-Gal reported in vitro also occurs in vivo and in other plants, and confirm the involvement of ßIII-Gal in the cell wall autolysis process. An increase in the homogalacturonan content of transgenic tuber cell walls was also observed by Fourier transform infrared spectroscopy (FTIR) analysis.
    Reduction of starch granule size by expression of an engineered tandem starch-binding domain in potato plants
    Ji, Q. ; Oomen, R.J.F.J. ; Vincken, J.P. ; Bolam, D.N. ; Gilbert, H.J. ; Suurs, L.C.J.M. ; Visser, R.G.F. - \ 2004
    Plant Biotechnology Journal 2 (2004)3. - ISSN 1467-7644 - p. 251 - 260.
    specificity - sequence - cellulose - xylanase - modules - mutant - tissue - gene
    Granule size is an important parameter when using starch in industrial applications. An artificial tandem repeat of a family 20 starch-binding domain (SBD2) was engineered by two copies of the SBD derived from Bacillus circulans cyclodextrin glycosyltransferase via the Pro-Thr-rich linker peptice from Xyn10A from Cellulomonas fimi. SBD2 and a single SBD were introduced into the amylose-free potato mutant, amf, using appropriate signal sequences. The accumulation of SBD2 into transgenic starch granules was much higher than that of SBD. In a number of transformants, particularly amfSS3, the starch granules were much smaller than in control plants. The amfSS3 mean granule size was 7.8 mum, compared with 15.2 mum in the control, whereas other starch properties were unaltered. This new starch combines the advantage of the high purity of potato starch with that of the small granule size of other crop species, such as cassava, taro and wheat. This starch may find application in the manufacture of biodegradable plastic films. Both genes were also expressed in Escherichia coli and the affinity for soluble starch of the purified recombinant proteins was determined. SBD2 had an approximately 10-fold higher affinity for starch than SBD, indicating that the two appended SBDs act in synergy when binding to their target polysaccharide ligand.
    Modulation of the cellulose content of tuber cell walls by antisense expression of different potato (Solanum tuberosum L.) CesA clones
    Oomen, R.J.F.J. ; Tzitzikas, E. ; Bakx, E.J. ; Straatman-Engelen, I. ; Bush, M.S. ; Mccann, M.C. ; Schols, H.A. ; Visser, R.G.F. ; Vincken, J.P. - \ 2004
    Phytochemistry 65 (2004)5. - ISSN 0031-9422 - p. 535 - 546.
    synthase gene-expression - acetobacter-xylinum - catalytic subunit - infrared-spectra - arabidopsis - polysaccharides - granule - mutants - plants - resistance
    Four potato cellulose synthase (CesA) homologs (StCesA1, 2, 3 and 4) were isolated by screening a cDNA library made from developing tubers. Based on sequence comparisons and the fact that all four potato cDNAs were isolated from this single cDNA-library, all four StCesA clones are likely to play a role in primary cell wall biosynthesis. Several constructs were generated to modulate cellulose levels in potato plants in which the granule-bound starch synthase promoter was used to target the modification to the tubers. The StCesA3 was used for up- and down-regulation of the cellulose levels by sense (SE-StCesA3) and antisense (AS-StCesA3) expression of the complete cDNA. Additionally, the class-specific regions (CSR) of all four potato cellulose synthase genes were used for specific down-regulation (antisense) of the corresponding CesA genes (csr1, 2, 3 and 4). None of the transformants showed an overt developmental phenotype. Sections of tubers were screened for altered cell wall structure by Fourier Transform Infrared microspectroscopy (FTIR) and exploratory Principal Component Analysis (PCA), and those plants discriminating from WT plants were analysed for cellulose content and monosaccharide composition. Several transgenic lines were obtained with mainly decreased levels of cellulose. These results show that the cellulose content in potato tubers can be reduced down to 40% of the WT level without affecting normal plant development, and that constructs based on the CSR alone are specific and sufficient to down-regulate cellulose biosynthesis. (C) 2004 Elsevier Ltd. All rights reserved.
    Overexpression of two different potato UDP-Glc-4-epimerases can increase the galactose content of potato tuber cell walls
    Oomen, R.J.F.J. ; Dao-Thi, B. ; Tzitzikas, E. ; Bakx, E.J. ; Schols, H.A. ; Visser, R.G.F. ; Vincken, J.P. - \ 2004
    Plant Science 166 (2004). - ISSN 0168-9452 - p. 1097 - 1104.
    synthase gene-expression - molecular-cloning - escherichia-coli - plants - arabidopsis - saccharomyces - inhibition - polysaccharides - transcription - biosynthesis
    UDP-glucose 4-epimerases (UGE) catalyze the reversible conversion of UDP-glucose to UDP-galactose. Two potato UGE genes (StUGE45 and StUGE51) were isolated from a potato cDNA library using the Arabidopsis thaliana UGE1 cDNA as a probe. The cDNA clones cluster differently in a phylogenetic tree of plant epimerases. StUGE51 showed higher expression than StUGE45, particularly, in older tubers, flowers, stems and in vitro plants. Transgenic potato plants were generated to examine the effect of modified UGE expression on the amount of cell wall galactose. Sense expression of the two StUGE clones in potato gave plants with no overt developmental phenotype. In contrast to WT plants, a large number of transformants had the ability to overcome the toxic effect of galactose in the culture medium during in vitro growth. The UGE45 transformants showed a clear correlation of increased UGE RNA expression levels with this tolerance to galactose, whereas the UGE51 transformants did not. The elevated UGE expression in the transformants resulted in an increased galactose content in potato tuber cell walls. This effect was more profound for the UGE45 transformants than for the UGE51 ones. Our results suggest that the two potato UGEs have different biochemical properties, and that they have a different function in plant development. (C) 2004 Elsevier Ireland Ltd. All rights reserved.
    Pectic - the hairy thing
    Vincken, J.P. ; Schols, H.A. ; Oomen, R.J.F.J. ; Beldman, G. ; Voragen, A.G.J. - \ 2003
    In: Advances in pectin and Pectinase Research / Voragen, A.G.J., Schols, H.A., Visser, R.G.F., Dordrecht : Kluwer - ISBN 9781402011443 - p. 47 - 59.
    Exploring the use of cDNA-AFLP with leaf protoplasts as a tool to study primary cell wall biosynthesis in potato
    Oomen, R.J.F.J. ; Bergervoet-van Deelen, J.E.M. ; Bachem, C.W.B. ; Visser, R.G.F. ; Vincken, J.P. - \ 2003
    Plant Physiology and Biochemistry 41 (2003). - ISSN 0981-9428 - p. 965 - 971.
    carrot protoplasts - gene-expression - fusion
    An RNA fingerprinting study of potato leaf protoplasts was performed to explore its suitability for identifying candidate genes involved in primary cell wall biosynthesis. Microscopic analysis, using calcofluor white to stain cellulose, showed that the protoplasts generated a new cell wall in the first 18 h after transfer to a culture medium. Complementary DNA-amplified fragment length polymorphism (cDNA-AFLP) was used to visualise differential gene expression at five distinct time-points within these first 18 h. In vitro plants (with and without exposure to severe physical damage) served as controls. Around 8500 transcript derived fragments (TDFs) were visualised which showed varying expression patterns in the protoplasts and controls. In total 156 TDFs were isolated, sequenced and used to search for homologies. Over 50% of these TDFs showed homology to described genes, involved in several general plant processes. However, only one cell wall related TDF (a pectin esterase) was found. Our results showed that even though the protoplasts actively regenerate a new cell wall, this did not result in highly increased expression of genes involved in cell wall biosynthesis or modification. (C) 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.
    If homogalacturonan were a side chain of rhamnogalacturonan I. Implications for cell wall architecture
    Vincken, J.P. ; Schols, H.A. ; Oomen, R.J.F.J. ; Mccann, M.C. ; Ulvskov, P. ; Voragen, A.G.J. ; Visser, R.G.F. - \ 2003
    Plant Physiology 132 (2003). - ISSN 0032-0889 - p. 1781 - 1789.
    pectic polysaccharide - cross-linking - arabidopsis - adhesion - regions - 2,6-dichlorobenzonitrile - esterification - biosynthesis - features - arabinan
    Pectin : the hairy thing : evidence that homogalacturonan is a side chain of rhamnogalacturonan I
    Vincken, J.P. ; Schols, H.A. ; Oomen, R.J.F.J. ; Beldman, G. ; Visser, R.G.F. ; Voragen, A.G.J. - \ 2003
    In: Advances in Pectin and Pectinase Research : 2nd International Symposium on Pectins and Pectinases, Rotterdam, 2001 / F. Voragen, H. Schols & R. Visser Dordrecht : Kluwer Academic Publishers - ISBN 9781402011443 - p. 47 - 61.
    pectinen - galactanen - celwanden - pectins - galactans - cell walls
    In vitro degradation studies of pectic polysaccharides with novel fungal pectinases, investigations in which these polymers were treated with dilute acid, and microscopic analysis of extracted pectins have provided clues on how these polysaccharides are linked. Therefore it is believed that pectin is not an extended backbone consisting of homogalacturonan and rhamnogalacturonan regions, but rather a rhamnogalacturonan with neutral sugar and homogalacturonan side chains
    Towards unravelling the biological significance of the individual components of pectic hairy regions in plants
    Oomen, R.J.F.J. ; Vincken, J.P. ; Bush, M.S. ; Skjot, M. ; Voragen, C.H.L. ; Ulvskov, P. ; Voragen, A.G.J. ; Mccann, M.C. ; Visser, R.G.F. - \ 2003
    In: Advances in Pectin and Pectinase Research : 2nd International Symposium on Pectins and Pectinases, Rotterdam, 2001 / F. Voragen, H. Schols & R. Visser Dordrecht : Kluwer Academic Publishers - ISBN 9781402011443 - p. 15 - 34.
    pectinen - galactanen - celwanden - poriëngrootte - plantenweefsels - pectins - galactans - cell walls - pore size - plant tissues
    This review compares the results from the developmental studies together with those from mutagenized and genetically modified plants with compositional alterations to the hairy region
    In planta modification of the potato tuber cell wall
    Oomen, R.J.F.J. - \ 2003
    Wageningen University. Promotor(en): Richard Visser, co-promotor(en): Jean-Paul Vincken. - [S.I.] : S.n. - ISBN 9789058087843 - 131
    solanum tuberosum - aardappelen - genetische modificatie - celwanden - polygalacturonase - celwandstoffen - cellulose - enzymactiviteit - genexpressie - pectinen - plantenveredeling - solanum tuberosum - potatoes - cell walls - cell wall components - genetic engineering - pectins - polygalacturonase - cellulose - enzyme activity - gene expression - plant breeding

    Apart from its well known uses in the human diet a large amount of the grown potatoes (about one third in the Netherlands) is used for the isolation of starch which is used in several food and non-food applications. The cell wall fibres comprise a large portion of the waste material remaining after the starch isolation process. While cell wall fibres from some other plant species are used in food and non-food industry, a structural alteration of the potato fibres is necessary before similar applications are possible. However, before it is possible to generate plants with a tailor-made cell wall composition, questions concerning the best approach have to be answered and the necessary tools will have to be identified and made available. This thesis describes the results of a study investigating the possibilities to generate transgenically modified potato plants with an altered cell wall composition. These experiments were mostly focussed on altering pectin composition. This is particularly interesting because several studies already showed that many different pectin structures occur in specific plants, plant tissues and developmental stages. Plants with a specific alteration in pectin structure may aid in revealing the biological significance of these different structures. Additionally, the possibility to produce a particular pectin structure may be useful for the food industry, in which pectins from other plant species are already used as a gelling agent.

    At the start of the work described in this thesis only few genes involved in cell wall biosynthesis were identified which favoured the heterologous expression of fungal pectin degrading enzymes. A rhamnogalacturonan lyase ( e RGL) from Aspergillus aculeatus , which is able to cleave the rhamnogalacturonan I (RG I) at specific sites, was introduced. The e RGL was successfully expressed (under control of the granule-bound starch synthase promoter) and translated into an active protein, demonstrated by e RGL activity in the tuber extracts. These tubers showed clear morphological alterations, including radial swelling of the periderm cells and development of intercellular spaces in the cortex. Sugar compositional analysis and antibody labelling studies showed a large reduction in galactan and arabinan side-chains of RG I. These data show the possibility of specifically modifying cell wall polysaccharide structures by the introduction of such a pectin degrading enzyme. Additionally, the results suggest that RG I has an important role in anchoring galactans and arabinans at particular regions in the wall and in normal development of the periderm. The utility of these transgenic plants in answering questions concerning the biological importance of cell wall polysaccharides is evident.

    Apart from modifying the cell wall composition by the introduction of pectin degrading enzymes two experiments were performed focussed on interference with the biosynthetic machinery of the plant cell wall at different levels. The first study concerns the modulation of cellulose synthase ( CesA ) gene expression. Since this enzyme is polymerising theb-1,4 glucan chains forming cellulose, its altered expression is likely to directly affect the level of cellulose in the wall. In the second study the expression of the UDP-Glc-4-epimerase ( UGE ) was modulated. The UGE is responsible for the conversion of UDP-glucose to UDP-galactose and vice-versa. Its altered expression is likely to affect the amount of cell wall bound galactan.

    Four CesA genes were isolated from potato and one full length cDNA clone was used for up- and down-regulation of the corresponding RNA expression levels controlled by the granule-bound starch synthase promoter. Fourier Transform Infra-Red microspectroscopy (FTIR) was used for the identification of transformants with altered levels of cellulose in their tuber cell walls in comparison to WT plants. A further quantification of these results, by measuring the cellulose content in the cell wall material, showed that by modulating the CesA expression levels, tubers with levels of cellulose ranging from 50 to 200% of the WT amount were obtained. Especially the increase in cellulose is quite remarkable and in contradiction with the general believe that expression of more than one CesA gene (and possibly even more genes) is necessary to achieve such a modification. By using a specific region of the other three CesA genes in antisense experiments we managed to individually down regulate these genes and concomitantly the cellulose levels in the tubers of these plants. The use of this so-called class specific region (CSR), which is only present in plant cellulose synthases and is believed to determine the genetic difference between the different CesA genes in one plant, showed to be sufficient to down regulate the corresponding gene. In contrast to many other plants and plant systems, depletion of cellulose (to 50% of WT level) in potato tubers did not result in any phenotypic alterations. However, our potato plants were grown at normal conditions while some of the cellulose synthase mutants only revealed a phenotype when grown at restrictive conditions. Another important result is the fact that not all potato transformants with decreased cellulose levels show modifications in their pectin composition. This indicates a delicate balance between cellulose and pectin levels and that an altered pectin composition in plants with depleted cellulose is not necessarily a response upon reduced strength of the cell wall.

    For the UDP-Glc-4-epimerase two potato cDNA clones ( StUGE45 and StUGE51 ) were identified and used for overexpression in potato tubers. The increased levels of cell wall bound galactan in these tubers indicates the importance of UDP-galactose levels for galactan deposition in the cell wall. Additionally these plants showed a small decrease in the amount of galacturonan. This suggests that alterations in the UDP-galactose pool size can influence the levels of nucleotide sugars which are used for the synthesis of other polysaccharides. Additionally, the elevated expression levels of the two UGE s showed to have different effects, which suggests that they have a different function in plant development. Further research has to show whether other polysaccharides than cell wall galactan are affected by this decrease in galactose. Xyloglucan and galactomannan also contain galactosyl residues and the decrease does not necessarily affect the levels of RG I bound galactan.

    Both these studies show the possibility to induce alterations in the cell wall composition by interfering with the biosynthetic machinery. Identification of more genes involved in cell wall biosynthesis is necessary to enable new studies in the future. An RNA fingerprinting experiment was performed to investigate the possibility of identifying new genes involved in primary cell wall biosynthesis. Potato leaf protoplasts showed to regenerate a new cell wall in the first 18h after transfer to a culture medium. At 5 distinct time-points RNA was isolated and the expressed genes were visualised using cDNA-AFLP. Around 8500 transcript derived fragments (TDFs) were visualised from which 156 were isolated and sequenced. However, no cell wall related TDFs were identified. This indicates that even though the protoplasts actively regenerate a new cell wall, this did not result in highly increased expression of genes involved in cell wall biosynthesis or modification.

    In summary the experiments described in this thesis showed that different approaches can be used to generate a modified cell wall composition in potato tubers. These genetically modified plants have shown to be an interesting study material for unravelling the biological function of different cell wall polysaccharide structures. Additionally these transformants obviously showed that the potato tuber cell wall is amenable to genetic modification. There is a wide range of wall modifications which is tolerated by the tubers, which may hold a promise for the future in valorising the fibre fraction of potato after starch isolation.

    In muro fragmentation of the rhamnogalacturonan I backbone in potato (Solanum tuberosum L.) results in a reduction and altered location of the galactan and arabinan side-chains and abnormal periderm development
    Oomen, R.J.F.J. ; Doeswijk-Voragen, C.H.L. ; Bush, M.S. ; Vincken, J.P. ; Borkhardt, B. ; Broek, L.A.M. van den; Corsar, J. ; Ulvskov, P. ; Voragen, A.G.J. ; McCann, M.C. ; Visser, R.G.F. - \ 2002
    The Plant Journal 30 (2002)4. - ISSN 0960-7412 - p. 403 - 413.
    Rhamnogalacturonan (RG) I is a branched pectic polysaccharide in plant cell walls. Rhamnogalacturonan lyase (eRGL) from Aspergillus aculeatus is able to cleave the RG I backbone at specific sites. Transgenic potato (Solanum tuberosum L.) plants were made by the introduction of the gene encoding eRGL, under the control of the granule-bound starch synthase promoter. The eRGL protein was successfully expressed and translated into an active form, demonstrated by eRGL activity in the tuber extracts. The transgenic plants produced tubers with clear morphological alterations, including radial swelling of the periderm cells and development of intercellular spaces in the cortex. Sugar compositional analysis of the isolated cell walls showed a large reduction in galactosyl and arabinosyl residues in transgenic tubers. Immunocytochemical studies using the LM5 (galactan) and LM6 (arabinan) antibodies also showed a large reduction in galactan and arabinan side-chains of RG I. Most of the remaining LM5 epitopes were located in the expanded middle lamella at cell corners of eRGL tubers, which is in contrast to their normal location in the primary wall of wild type tubers. These data suggest that RG I has an important role in anchoring galactans and arabinans at particular regions in the wall and in normal development of the periderm.
    Method for remodelling cell wall polysaccharide structures in plants
    Ulvskov, P. ; Schols, H.A. ; Visser, R.G.F. ; Borkhardt, B. ; Sorensen, S.O. ; Oomen, R.J.F.J. ; Vincken, J.P. ; Mc Cann, M. ; Skjot, M. ; Bush, M.S. ; Voragen, C.H.L. ; Beldman, G. - \ 2001
    Octrooinummer: WO0159137, gepubliceerd: 2001-08-16.
    Methods for providing transgenic plants and parts hereof that, relative to the wild type state, is modified in a complex cell wall polysaccharide structure including pectins and hemicelluloses, the modification being in the overall glycosidic linkage pattern or the monosaccharide profile, comprising transforming a plant cell with a nucleotide sequence that causes an altered production of a complex cell wall polysaccharide-modifying enzyme such as endo-rhamnogalacturonan hydrolase, an endo-rhamnogalacturonan lyase, an endo-galactanase, an endo-arabinanase, an arabinofuranosidase, a galactosidase such as a beta-galactosidase, a xylosidase and an exo-galacturosidase. The modification can occur in vivo or post harvest, in which latter case the modifying enzyme is separated in the growing plant from its substrate, e.g. by targeting the enzyme to the Golgi, the endoplasmic reticulum or a vacuole, or is in a form that is inactive in the plant. After harvest the enzyme is brought into contact with its substrate or it is activated to provide the desired post harvest modification of the cell wall polysaccharide. The transgenic plant materials have improved functionalities and are useful in food and feed manufacturing and as pharmaceutically or medically active substances.
    Antisense suppression of a potato alpha-SNAP homologue leads to alterations in cellular development and assimilate distribution
    Bachem, C.W.B. ; Oomen, R.J.F.J. ; Kuyt, S. ; Horvath, B.M. ; Claassens, M.M.J. ; Vreugdenhil, D. ; Visser, R.G.F. - \ 2000
    Plant Molecular Biology 43 (2000)4. - ISSN 0167-4412 - p. 473 - 482.
    Using the cDNA-AFLP method, we have isolated a transcript-derived fragment (TDF) which shows a differential expression pattern during tuber organogenesis of Solanum tuberosum L. The TDF was used to isolate a cDNA clone carrying a 1.5 kb insert and potentially coding for a 32.5 kDa peptide which, by homology, represents a potato homologue of an alpha-snap gene and has been designated Stsnap. Northern analysis showed that the Stsnap gene is expressed in actively dividing tissues throughout the potato plant. Analysis of genomic DNA from potato revealed that the Stsnap gene is likely to be a single-copy gene. The expression of antisense Stsnap cDNA under the control of the CaMV 35S promoter results in plants with an altered morphology such as curled leaves. Several of these transgenic lines also display cellular and developmental abnormalities with distinct changes in assimilate transport including accumulation of starch and soluble sugars in source leaves. We argue that these findings are consistent with the hypothetical function of the StSNAP gene product in vesicle targeting and fusion during plant development.
    Transcript imaging with cDNA-AFLP: a step by step protocol.
    Bachem, C.W.B. ; Oomen, R.J.F.J. ; Visser, R.G.F. - \ 1998
    Plant Molecular Biology Reporter 16 (1998). - ISSN 0735-9640 - p. 157 - 173.
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