Chloroplasts autophagy during senescence of individually darkened leaves

Shinya Wada, Hiroyuki Ishida

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)

Abstract

We recently reported that autophagy plays a role in chloroplasts degradation in individually-darkened senescing leaves. Chloroplasts contain approximately 80% of total leaf nitrogen, mainly as photosynthetic proteins, predominantly ribulose 1, 5-bisphosphate carboxylase/oxygenase (Rubisco). During leaf senescence, chloroplast proteins are degraded as a major source of nitrogen for new growth. Concomitantly, while decreasing in size, chloroplasts undergo transformation to non-photosynthetic gerontoplasts. Likewise, over time the population of chloroplasts (gerontoplasts) in mesophyll cells also decreases. While bulk degradation of the cytosol and organelles is mediated by autophagy, the role of chloroplast degradation is still unclear. In our latest study, we darkened individual leaves to observe chloroplast autophagy during accelerated senescence. At the end of the treatment period chloroplasts were much smaller in wild-type than in the autophagy defective mutant, atg4a4b-1, with the number of chloroplasts decreasing only in wild-type. Visualizing the chloroplast fractions accumulated in the vacuole, we concluded that chloroplasts were degraded by two different pathways, one was partial degradation by small vesicles containing only stromal-component (Rubisco containing bodies; RCBs) and the other was whole chloroplast degradation. Together, these pathways may explain the morphological attenuation of chloroplasts during leaf senescence and describe the fate of chloroplasts.

Original languageEnglish
Pages (from-to)565-567
Number of pages3
JournalPlant Signaling and Behavior
Volume4
Issue number6
DOIs
Publication statusPublished - 2009 Jun

Keywords

  • Arabidopsis
  • Autophagy
  • Chloroplast
  • Dark treatment
  • Leaf senescence
  • Nutrients recycling

ASJC Scopus subject areas

  • Plant Science

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