Abstract
A predominant physiological change that occurs during leaf senescence is a decrease in photosynthetic efficiency. An optimal organization of photosynthesis complexes in plant leaves is critical for efficient photosynthesis. However, molecular mechanisms for regulating photosynthesis complexes during leaf senescence remain largely unknown. Here we tracked photosynthesis complexes alterations during leaf senescence in Arabidopsis thaliana. Grana stack is significantly thickened and photosynthesis complexes were disassembled in senescing leaves. Defects in STN7 and CP29 led to an altered chloroplast ultrastructure and a malformation of photosynthesis complex organization in stroma lamella. Both CP29 phosphorylation by STN7 and CP29 fragmentation are highly associated with the photosynthesis complex disassembly. In turn, CP29 functions as a molecular glue to facilitate protein complex formation leading phosphorylation cascade and to maintain photosynthetic efficiency during leaf senescence. These data suggest a novel molecular mechanism to modulate leaf senescence via CP29 phosphorylation and fragmentation, serving as an efficient strategy to control photosynthesis complexes.
Highlights
A predominant physiological change that occurs during leaf senescence is a decrease in photosynthetic efficiency
photosystem II (PSII) core accompanied by LHCII that is interlinked by Chlorophyll bound protein (CP) 24 (CP24), CP26 and CP2915,16
Chloroplast ultrastructure was first analyzed in Arabidopsis leaves at five dates (Days after emergence (DAE) 18, 22, 26, 30, and 34) along leaf senescence using transmission electron microscopy to uncover the ultrastructure of chloroplast transition to gerontoplast
Summary
A predominant physiological change that occurs during leaf senescence is a decrease in photosynthetic efficiency. One hypothesis suggests that decrease in photosynthetic efficiency in older leaves results from alterations in the photosynthetic apparatus during leaf senescence[11,12,13] It is critical organizing photosynthetic protein complexes to modulate photosynthesis efficiency. PSI, PSII, cytochrome b6f (Cyt b6f), and ATP synthase are the central components of electron transport process during photosynthesis These basic protein complexes are selectively assembled in the thylakoid membrane in order to optimize photosynthetic efficiency[14]. Defects in a number of PSI protein components led to a premature decrease in chlorophyll concentration in response to both natural and dark-induced senescence, suggesting that alterations in the photosynthetic apparatus can affect the leaf senescence process.
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