|Expression of Arabidopsis plastidial phosphoglucomutase in tobacco stimulates
photosynthetic carbon flow into starch synthesis.
J. Plant. Physiol. 169: 1454-1462. 2012.
K. Uematsu, N. Suzuki, T. Iwamae, M. Inui and H. Yukawa.
|Phosphoglucomutase (PGM, EC 18.104.22.168) is one of the enzymes constituting
the carbohydrate synthesis pathway in higher plants. It catalyzes the reversible
conversion of glucose 6-phosphate (Glc6P) to glucose 1-phosphate (Glc1P).
Previously, metabolic turnover analysis using (13)CO(2) in tobacco leaves
demonstrated that conversion of Glc6P to Glc1P may limit carbon flow into
carbohydrate synthesis. In order to assess the effects of PGM, Arabidopsis thaliana cytosolic or plastidial PGM was expressed under the control of cauliflower mosaic virus 35S promoter in tobacco plants (Nicotiana tabacum cv. Xanthi) and phenotypic analysis was performed. The transgenic plants
expressing Arabidopsis plastidial PGM showed 3.5-8.2-fold higher PGM activity
than that of wild-type, and leaf starch and sucrose contents increased
2.3-3.2-fold and 1.3-1.4-fold, respectively over wild-type levels. In vivo(13)C-labeling experiments indicated that photosynthetically fixed carbon
in the transgenic plants could be converted faster to Glc1P and adenosine
5'-diphosphate glucose than in wild-type, suggesting that elevation of
plastidial PGM activity should accelerate conversion of Glc6P to Glc1P
in chloroplasts and increase carbon flow into starch. On the other hand,
transgenic plants expressing Arabidopsis cytosolic PGM showed a 2.1-3.4-fold
increase in PGM activity over wild-type and a decrease of leaf starch content,
but no change in sucrose content. These results suggest that plastidial
PGM limits photosynthetic carbon flow into starch.
Copyright (c) 2012 Elsevier GmbH. All rights reserved.