Abstract
Effects of an overexpression of RBCS on Rubisco content, photosynthesis and plant growth were examined in rice (Oryza sativa L.). Rubisco content in the transformant was significantly greater in the uppermost, fully expanded leaves, but decreased to levels similar to those in wild-type plants in the lower leaves. Although the activation state of Rubisco was lower in the uppermost, fully expanded leaves of the transformant, it recovered to its full level in the lower leaves. As a result, the photosynthetic rate did not differ in leaves at the same position between these genotypes. Similarly, whole plant biomass did not differ between these genotypes. Thus, we conclude that although the overexpression of RBCS led to an enhancement of Rubisco protein content in the uppermost, fully expanded leaves, it does not result in increased photosynthetic rates or plant biomass, due to an apparent down-regulation in its activation state.
