Abstract
It has been suggested that Rubisco might be degraded within or outside of intact chloroplasts because the amount of Rubisco decreases much faster than the decrease in chloroplast number. In this study, we investigated the possibility that Rubisco is degraded outside of chloroplasts.
By immunocytochemical analysis, besides the chloroplast stroma, we recently found that Rubisco was localized in small spherical bodies having 0.4-1.2 μm in diameter. These Rubisco-containing bodies (RCB) were also found in the specimens prepared by high-pressure freezing and freeze substitution methods. RCB seemed to be derived from chloroplasts because the protrusion of the chloroplast envelope enclosing the stromal portion was seen. RCB contained the other stromal protein, glutamine synthetase, but not thylakoidal proteins. The appearance of RCB was most remarkable when the amount of Rubisco started to decrease. These results suggest that RCB could take responsibility for the Rubisco degradation outside of the chloroplast during leaf senescence.
