Rubisco and photosynthesis in rice
2005
Makino, A.(Tohoku Univ., Sendai (Japan))
Genetic modification to enhance Rubisco efficiency would have great agronomic importance as a prospect to improve photosynthesis. The specific activity of Rubisco from rice is substantially lower than that in other plants. Since the difference in Rubisco-specific activity reflects a difference in the photosynthetic rate at atmospheric CO2 levels, the lower specific activity from rice provides the possibility to improve leaf photosynthesis by the introduction of a more efficient Rubisco into rice. An attempt to increase the Rubisco content by overexpressing the rbcS gene showed increases in the Rubisco content for a given leaf N content in rice. However, it led to an imbalance among the in vivo capacities of Rubisco and other photosynthetic-limiting factors. To maintain this balance, the enhancement of the cytochrome b6/f complex content may be required as a determinant for RuBP regeneration. Another approach to improving photosynthesis is to introduce C4 characteristics into rice. Optimal protein allocation with a lower amount of Rubisco of the high-Vmax/Km (CO2) type, as well as Kranz leaf anatomy, is important for the improvement of photosynthesis.
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