PLANT PHYSIOLOGY , Vol 115, Issue 2 471-475, Copyright © 1997 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Antisense Repression of Both ADP-Glucose Pyrophosphorylase and Triose Phosphate Translocator Modifies Carbohydrate Partitioning in Potato Leaves
A. Hattenbach, B. Muller-Rober, G. Nast and D. Heineke
Institut fur Biochemie der Pflanze, Untere Karspule 2, D-37073 Gottingen, Germany (A.H., D.H.)
Previous experiments have shown that carbohydrate partitioning in leaves of
potato (Solanum tuberosum L.) plants can be modified by antisense
repression of the triose phosphate translocator (TPT), favoring starch
accumulation during the light period, or by leaf-specific antisense
repression of ADP-glucose pyrophosphorylase (AGPase), reducing leaf starch
content. These experiments showed that starch and sucrose synthesis can
partially replace each other. To determine how leaf metabolism acclimates
to an inhibition of both pathways, transgenic potato (S. tuberosum L. cv
Desiree) plants, with a 30% reduction of the TPT achieved by antisense
repression, were transformed with an antisense cDNA of the small subunit of
AGPase, driven by the leaf-specific ST-LS1 promoter. These
double-transformed plants were analyzed with respect to their carbohydrate
metabolism, and starch accumulation was reduced in all lines of these
plants. In one line with a 50% reduction of AGPase activity, the rate of
CO2 assimilation was unaltered. In these plants the stromal level of triose
phosphate was increased, enabling a high rate of triose phosphate export in
spite of the reduction of the TPT protein by antisense repression. In a
second line with a 95% reduction of AGPase activity, the amount of
chlorophyll was significantly reduced as a consequence of the lowered
triose phosphate utilization capacity.
