Journal Article

Contribution of Fructose-1,6-bisphosphatase and Sedoheptulose-1,7-bisphosphatase to the Photosynthetic Rate and Carbon Flow in the Calvin Cycle in Transgenic Plants

Masahiro Tamoi, Miki Nagaoka, Yoshiko Miyagawa and Shigeru Shigeoka

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 47, issue 3, pages 380-390
Published in print March 2006 | ISSN: 0032-0781
Published online March 2006 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcj004
Contribution of Fructose-1,6-bisphosphatase and Sedoheptulose-1,7-bisphosphatase to the Photosynthetic Rate and Carbon Flow in the Calvin Cycle in Transgenic Plants

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To clarify the contributions of fructose-1,6-bisphosphatase (FBPase) and sedoheptulose-1,7-bisphosphatase (SBPase) separately to the carbon flux in the Calvin cycle, we generated transgenic tobacco plants expressing cyanobacterial FBPase-II in chloroplasts (TpF) or Chlamydomonas SBPase in chloroplasts (TpS). In TpF-11 plants with 2.3-fold higher FBPase activity and in TpS-11 and TpS-10 plants with 1.6- and 4.3-fold higher SBPase activity in chloroplasts compared with the wild-type plants, the amount of final dry matter was approximately 1.3-, 1.5- and 1.5-fold higher, respectively, than that of the wild-type plants. At 1,500 µmol m–2 s–1, the photosynthetic activities of TpF-11, TpS-11 and TpS-10 were 1.15-, 1.27- and 1.23-fold higher, respectively, than that of the wild-type plants. The in vivo activation state of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and the level of ribulose-1,5-bisphosphate (RuBP) in TpF-11, TpS-10 and TpS-11 were significantly higher than those in the wild-type plants. However, the transgenic plant TpF-9 which had a 1.7-fold higher level of FBPase activity showed the same phenotype as the wild-type plant, except for the increase of starch content in the source leaves. TpS-11 and TpS-10 plants with 1.6- and 4.3-fold higher SBPase activity, respectively, showed an increase in the photosynthetic CO2 fixation, growth rate, RuBP contents and Rubisco activation state, while TpS-2 plants with 1.3-fold higher SBPase showed the same phenotype as the wild-type plants. These data indicated that the enhancement of either a >1.7-fold increase of FBPase or a 1.3-fold increase of SBPase in the chloroplasts had a marked positive effect on photosynthesis, that SBPase is the most important factor for the RuBP regeneration in the Calvin cycle and that FBPase contributes to the partitioning of the fixed carbon for RuBP regeneration or starch synthesis.

Keywords: Calvin cycle; Fructose-1,6-bisphosphatase; Sedoheptulose-1,7-bisphosphatase; Transgenic plant.; AGPase, ADP-glucose pyrophosphorylase; BSA, bovine serum albumin; DHAP, dihydroxyacetone phosphate; DTT, dithiothreitol; E4P, erythlose 4-phosphate; F6P, fructose 6-phosphate; FBP, fructose 1,6-bisphosphate; FBPase, fructose-1,6-bisphosphatase; FBP/SBPase, fructose-1,6-/sedoheptulose-1,7-bisphosphatase; G6P, glucose 6-phosphate; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; PGA, 3-phosphoglycerate; PRK, phosphoribulokinase; PVP, polyvinylpyrrolidone; Rubisco, ribulose-1,5-bisphosphate carboxylase/oxygenase; RuBP, ribulose-1,5-bisphosphate; SBP, sedoheptulose 1,7-bisphosphate; SBPase, sedoheptulose-1,7-bisphosphatase; SPS, sucrose phosphate synthase; X5P, xylulose 5-phosphate.

Journal Article.  6735 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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