Present address: PlantTec Biotechnologie GmbH F and E, Hermannswerder 14, 14473 Potsdam, Germany.
Antisense inhibition of plastidial phosphoglucomutase provides compelling evidence that potato tuber amyloplasts import carbon from the cytosol in the form of glucose-6-phosphate
Article first published online: 25 DEC 2001
The Plant Journal
Volume 23, Issue 1, pages 43–53, July 2000
How to Cite
Tauberger, E., Fernie, A. R., Emmermann, M., Renz, A., Kossmann, J., Willmitzer, L. and Trethewey, R. N. (2000), Antisense inhibition of plastidial phosphoglucomutase provides compelling evidence that potato tuber amyloplasts import carbon from the cytosol in the form of glucose-6-phosphate. The Plant Journal, 23: 43–53. doi: 10.1046/j.1365-313x.2000.00783.x
- Issue published online: 25 DEC 2001
- Article first published online: 25 DEC 2001
- Received 7 March 2000; revised 19 April 2000; accepted 20 April 2000.
The aim of this work was to establish whether plastidial phosphoglucomutase is involved in the starch biosynthetic pathway of potato tubers and thereby to determine the form in which carbon is imported into the potato amyloplast. For this purpose, we cloned the plastidial isoform of potato PGM (StpPGM), and using an antisense approach generated transgenic potato plants that exhibited decreased expression of the StpPGM gene and contained significantly reduced total phosphoglucomutase activity. We confirmed that this loss in activity was due specifically to a reduction in plastidial PGM activity. Potato lines with decreased activities of plastidial PGM exhibited no major changes in either whole-plant or tuber morphology. However, tubers from these lines exhibited a dramatic (up to 40%) decrease in the accumulation of starch, and significant increases in the levels of sucrose and hexose phosphates. As tubers from these lines exhibited no changes in the maximal catalytic activities of other key enzymes of carbohydrate metabolism, we conclude that plastidial PGM forms part of the starch biosynthetic pathway of the potato tuber, and that glucose-6-phosphate is the major precursor taken up by amyloplasts in order to support starch synthesis.