Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the most abundant protein on Earth and is an essential component of the photosynthetic process of fixing CO2 into organic carbon. Rubisco is known to have a low catalytic rate, a primary factor explaining its high concentration in C3 plant leaves. Therefore, improving the Rubisco performance via quality control and/or quantity control is an obvious target for both increasing photosynthetic performance and nitrogen use efficiency. Recently, the introduction of a C4-Rubisco small subunit (rbcS) gene from sorghum into rice successfully produced chimeric Rubisco with a greater catalytic turnover rate of Rubisco (kcat) in the transgenic rice [1]. Also, single residues controlling enzymatic properties of Rubisco have been identified and successfully engineered to produce greater Rubisco proteins in Flaveria species from C3 to C4 catalysis [2]. Moreover, it has been reported that antisense reductions of Rubisco improved the photosynthetic rate at high CO2 concentrations in rice [3], as it may be possible to reallocate a large amount of nitrogen from Rubisco to the other photosynthetic components (e.g., Calvin cycle enzymes, electron transport systems). Thus, many attempts have been made to improve Rubisco function by genetic manipulation.