Repression of both isoforms of disproportionating enzyme leads to higher malto-oligosaccharide content and reduced growth in potato |
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Authors: | Henrik Lütken James R. Lloyd Mikkel A. Glaring Lone Baunsgaard Kristian Holst Laursen Anna Haldrup Jens Kossmann Andreas Blennow |
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Affiliation: | 1. VKR Research Centre Pro-Active Plants, Department of Plant Biology and Biotechnology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Denmark 2. Plant Research Department, Ris? National Laboratory, Frederiksborgvej 399, 4000, Roskilde, Denmark 3. Crop Sciences, Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen, H?jbakkeg?rd Alle 9, 2630, Taastrup, Denmark 4. Institute of Plant Biotechnology, Department of Genetics, University of Stellenbosch, Private Bag X1, 7602, Matieland, Stellenbosch, South Africa 5. Plant and Soil Science, Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Denmark
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Abstract: | Two glucanotransferases, disproportionating enzyme 1 (StDPE1) and disproportionating enzyme 2 (StDPE2), were repressed using RNA interference technology in potato, leading to plants repressed in either isoform individually, or both simultaneously. This is the first detailed report of their combined repression. Plants lacking StDPE1 accumulated slightly more starch in their leaves than control plants and high levels of maltotriose, while those lacking StDPE2 contained maltose and large amounts of starch. Plants repressed in both isoforms accumulated similar amounts of starch to those lacking StDPE2. In addition, they contained a range of malto-oligosaccharides from maltose to maltoheptaose. Plants repressed in both isoforms had chlorotic leaves and did not grow as well as either the controls or lines where only one of the isoforms was repressed. Examination of photosynthetic parameters suggested that this was most likely due to a decrease in carbon assimilation. The subcellular localisation of StDPE2 was re-addressed in parallel with DPE2 from Arabidopsis thaliana by transient expression of yellow fluorescent protein fusions in tobacco. No translocation to the chloroplasts was observed for any of the fusion proteins, supporting a cytosolic role of the StDPE2 enzyme in leaf starch metabolism, as has been observed for Arabidopsis DPE2. It is concluded that StDPE1 and StDPE2 have individual essential roles in starch metabolism in potato and consequently repression of these disables regulation of leaf malto-oligosaccharides, starch content and photosynthetic activity and thereby plant growth possibly by a negative feedback mechanism. |
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