Repression of both isoforms of disproportionating enzyme leads to higher malto-oligosaccharide content and reduced growth in potato

• Published in: Planta Vol. 232; no. 5; pp. 1127 - 1139
• Main Authors: Lütken, Henrik, Lloyd, James R, Glaring, Mikkel A, Baunsgaard, Lone, Laursen, Kristian Holst, Haldrup, Anna, Kossmann, Jens, Blennow, Andreas
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Berlin/Heidelberg : Springer-Verlag 01-10-2010; Springer-Verlag; Springer; Springer Nature B.V
• Subjects: Agriculture; Arabidopsis - genetics; Arabidopsis - metabolism; Biological and medical sciences; Biomedical and Life Sciences; Chlorophyll - metabolism; Chlorophylls; Disproportionating enzyme 1; Disproportionating enzyme 2; Ecology; Enzymes; Forestry; Fundamental and applied biological sciences. Psychology; Geometric lines; Glycogen Debranching Enzyme System - genetics; Glycogen Debranching Enzyme System - metabolism; Immunoblotting; Isoenzymes - genetics; Isoenzymes - metabolism; Leaves; Life Sciences; Malto-oligosaccharides; Nicotiana - genetics; Nicotiana - metabolism; Oligosaccharides - metabolism; Original Article; Phenotypes; Photosystem; Plant growth; Plant Proteins - genetics; Plant Proteins - metabolism; Plant Sciences; Plants; Potatoes; Protein isoforms; Repression; Solanum tuberosum - enzymology; Solanum tuberosum - genetics; Solanum tuberosum - growth & development; Solanum tuberosum - metabolism; Starch; Starches; Translocation; Tubers; Potato; Photosystem; Disproportionating enzyme 1; Starch; Disproportionating enzyme 2; Malto-oligosaccharides; 4-α-Glucanotransferase; Growth rate; Enzyme; Transferases; Oligosaccharide; Glycosyltransferases; Plant biology; Repression; Content; Hexosyltransferases
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-010-1245-3

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.