Abstract
During leaf senescence, chloroplast proteins are degraded as a major source of nitrogen for new growth, while chloroplasts gradually shrink and decrease in number. Autophagy is a bulk degradation of the cytosol and organelles. We previously demonstrated that vesicles called Rubisco-containing bodies (RCB) are produced by chloroplasts and transported into the vacuole by autophagy. In this study, we investigated the chloroplasts degradation pathway by autophagy in detail.
Using wild-type and autophagy defected mutant Arabidopsis, individually darkened leaves were used to observe senescence and chloroplast degradation. During the 5-d treatment, the number and size of chloroplasts decreased in wild-type, while the number remained constant and the size decrease was suppressed in the mutant. In the vacuole of wild-type cells, whole chloroplasts accumulated as well as RCB. These results demonstrate the two distinct chloroplast degradation pathways by autophagy, one for whole chloroplasts and one for RCB.
