Chlorophyll catabolism precedes changes in chloroplast structure and proteome during leaf senescence

Eyal Tamary, Reinat Nevo, Leah Naveh, Smadar Levin-Zaidman, Vladimir Kiss, Alon Savidor, Yishai Levin, Yoram Eyal, Ziv Reich, Zach Adam

Research output: Contribution to journalArticlepeer-review

Abstract

The earliest visual changes of leaf senescence occur in the chloroplast as chlorophyll is degraded and photosynthesis declines. Yet, a comprehensive understanding of the sequence of catabolic events occurring in chloroplasts during natural leaf senescence is still missing. Here, we combined confocal and electron microscopy together with proteomics and biochemistry to follow structural and molecular changes during Arabidopsis leaf senescence. We observed that initiation of chlorophyll catabolism precedes other breakdown processes. Chloroplast size, stacking of thylakoids, and efficiency of PSII remain stable until late stages of senescence, whereas the number and size of plastoglobules increase. Unlike catabolic enzymes, whose level increase, the level of most proteins decreases during senescence, and chloroplast proteins are overrepresented among these. However, the rate of their disappearance is variable, mostly uncoordinated and independent of their inherent stability during earlier developmental stages. Unexpectedly, degradation of chlorophyll-binding proteins lags behind chlorophyll catabolism. Autophagy and vacuole proteins are retained at relatively high levels, highlighting the role of extra-plastidic degradation processes especially in late stages of senescence. The observation that chlorophyll catabolism precedes all other catabolic events may suggest that this process enables or signals further catabolic processes in chloroplasts.

Original languageAmerican English
Article numbere00127
Number of pages18
JournalPlant Direct
Volume3
Issue number3
Early online date20 Mar 2019
DOIs
StatePublished - Mar 2019

Keywords

  • Arabidopsis
  • chlorophyll
  • chloroplast
  • photosynthesis
  • plastoglobule
  • senescence
  • thylakoid

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics
  • Ecology
  • Biochemistry, Genetics and Molecular Biology (miscellaneous)
  • Plant Science

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