Abstract
For autotrophic plants, recycling of nutrients and energy is especially important to survive under severe environments. Much of the total leaf nitrogen is allocated to chloroplasts, especially to Rubisco. During senescence and times of stress such as starvation, chloroplast proteins are rapidly degraded and their nitrogen and carbon are recycled.
While it is considered that bulk degradation of proteins and nutrient recycling in plants occurs mainly by autophagy, its actual role is still unclear. We have studied a role of autophagy on the degradation of chloroplast proteins since Rubisco-containing bodies (RCBs) were found in senescent leaves. RCBs were mobilized to the vacuole for the degradation by an ATG -gene dependent macroautophagy. Following RCBs, shrunk chloroplasts were also transported into the vacuole by autophagy when leaf senescence was promoted. RCB production was promoted by deficiency of leaf carbon but not nitrogen, thus the regulation was distinct from non-RCB-type autophagy. In this presentation, we discuss how autophagy contributes to the degradation of chloroplasts and their proteins.
