Activity regulation and physiological impacts of maize C 4-specific phosphoenolpyruvate carboxylase overproduced in transgenic rice plants

Hiroshi Fukayama, Marshall D. Hatch, Tesshu Tamai, Hiroko Tsuchida, Sizue Sudoh, Robert T. Furbank, Mitsue Miyao

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81 Citations (Scopus)


Phosphoenolpyruvate carboxylase (PEPC) was overproduced in the leaves of rice plants by introducing the intact maize C4-specific PEPC gene. Maize PEPC in transgenic rice leaves underwent activity regulation through protein phosphorylation in a manner similar to endogenous rice PEPC but contrary to that occurring in maize leaves, being downregulated in the light and upregulated in the dark. Compared with untransformed rice, the level of the substrate for PEPC (phosphoenolpyruvate) was slightly lower and the product (oxaloacetate) was slightly higher in transgenic rice, suggesting that maize PEPC was functioning even though it remained dephosphorylated and less active in the light. 14CO2 labeling experiments indicated that maize PEPC did not contribute significantly to the photosynthetic CO 2 fixation of transgenic rice plants. Rather, it slightly lowered the CO2 assimilation rate. This effect was ascribable to the stimulation of respiration in the light, which was more marked at lower O 2 concentrations. It was concluded that overproduction of PEPC does not directly affect photosynthesis significantly but it suppresses photosynthesis indirectly by stimulating respiration in the light. We also found that while the steady-state stomatal aperture remained unaffected over a wide range of humidity, the stomatal opening under non-steady-state conditions was destabilized in transgenic rice.

Original languageEnglish
Pages (from-to)227-239
Number of pages13
JournalPhotosynthesis Research
Issue number2-3
Publication statusPublished - 2003
Externally publishedYes


  • C photosynthesis
  • Phosphoenolpyruvate carboxylase
  • Protein phosphorylation
  • Respiration
  • Transgenic rice

ASJC Scopus subject areas

  • Biochemistry
  • Plant Science
  • Cell Biology

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