Autophagy Plays a Role in Chloroplast Degradation during Senescence in Individually Darkened Leaves

作者：Wada Shinya; Ishida Hiroyuki^*; Izumi Masanori; Yoshimoto Kohki; Ohsumi Yoshinori; Mae Tadahiko; Makino Amane

来源：Plant Physiology, 2009, 149(2): 885-893.

DOI：10.1104/pp.108.130013

Chloroplasts contain approximately 80% of total leaf nitrogen and represent a major source of recycled nitrogen during leaf senescence. While bulk degradation of the cytosol and organelles in plants is mediated by autophagy, its role in chloroplast catabolism is largely unknown. We investigated the effects of autophagy disruption on the number and size of chloroplasts during senescence. When leaves were individually darkened, senescence was promoted similarly in both wild-type Arabidopsis (Arabidopsis thaliana) and in an autophagy-defective mutant, atg4a4b-1. The number and size of chloroplasts decreased in darkened leaves of wild type, while the number remained constant and the size decrease was suppressed in atg4a4b-1. When leaves of transgenic plants expressing stroma-targeted DsRed were individually darkened, a large accumulation of fluorescence in the vacuolar lumen was observed. Chloroplasts exhibiting chlorophyll fluorescence, as well as Rubisco-containing bodies, were also observed in the vacuole. No accumulation of stroma-targeted DsRed, chloroplasts, or Rubisco-containing bodies was observed in the vacuoles of the autophagy-defective mutant. We have succeeded in demonstrating chloroplast autophagy in living cells and provide direct evidence of chloroplast transportation into the vacuole.

• 出版日期2009-2