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Published on: July 21, 2018
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Determining the Rate-Limiting Step for Light-Responsive Redox Regulation in Chloroplasts
Keisuke Yoshida1, Toru Hisabori2
1Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Nagatsuta 4259-R1-8, Midori-ku, Yokohama 226-8503, Japan. yoshida.k.ao@m.titech.ac.jp.
Antioxidants (Basel, Switzerland)
|November 3, 2018
Summary
Chloroplasts use thiol-based redox regulation for light control. The reduction of target proteins like SBPase by ferredoxin-thioredoxin reductase (FTR) and thioredoxin (Trx) is a slow, rate-limiting step, affecting light-responsive functions.
Area of Science:
- Plant Physiology
- Biochemistry
- Photosynthesis Research
Background:
- Thiol-based redox regulation is crucial for chloroplasts to adapt to light changes.
- Ferredoxin-thioredoxin reductase (FTR) and thioredoxin (Trx) mediate light signals via reducing power.
- The rate-limiting step in this redox relay remains unidentified.
Purpose of the Study:
- To identify the bottleneck in the FTR/Trx redox cascade controlling chloroplast functions.
- To characterize the in vitro and in vivo redox behavior of key components.
- To understand the differential light-responsive regulation of target proteins.
Main Methods:
- In vitro reconstitution of the FTR/Trx redox cascade using recombinant Arabidopsis proteins.
- In vivo studies of redox states in Arabidopsis plants under varying light conditions.
- Characterization of redox kinetics for FTR, Trx, and target proteins (FBPase, SBPase, RCA).
Main Results:
- FTR and f-type Trx were rapidly reduced, independent of target proteins.
- Target proteins FBPase, SBPase, and RCA showed slower, differential reduction rates in vitro.
- In vivo, Trx family members rapidly reduced under high light, while targets reduced slowly and differentially.
Conclusions:
- Reducing power transfer from Trx to target proteins is the rate-limiting step in chloroplast redox regulation.
- This bottleneck confers distinct light-responsive redox behaviors on target proteins like SBPase.
- The findings elucidate the mechanism of light-adaptive control in chloroplasts.
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