|Alteration of photosynthate partitioning by high-level expression of phosphoglucomutase in tobacco chloroplasts.
Biosci. Biotechnol. Biochem. 76: 1315-1321. 2012.
K. Uematsu, N. Suzuki, T. Iwamae, M. Inui and H. Yukawa.
|Plastidial phosphoglucomutase (PGM) plays an important role in starch synthesis
and degradation. Nonetheless, the impact of enhanced plastidial PGM activity
on metabolism in photosynthetic tissue is yet to be elucidated. In this
study, we generated transplastomic tobacco plants overproducing Arabidopsis thaliana plastidial PGM (AtptPGM) in chloroplasts and analyzed the consequent metabolic
and physiological parameters in the transplastomic plants. AtptPGM accumulated
in the chloroplasts to up to 16% of total soluble protein in the leaves.
PGM activity in leaves increased 100-fold relative to that of wild-type
plants. The transplastomic plants were phenotypically indistinguishable
in their growth rates, photosynthetic activities, and starch synthesis
from wild-type plants, but hexose partitioning in the light period was
dramatically different. Furthermore, alteration of extracellular invertase
activity was observed in the lower leaves of the transplastomic plants.
These observations suggest that high-level expression of plastidial PGM
alters hexose partitioning in light periods via modification of extracellular