Abstract
Thiol-based redox regulation is a posttranslational protein modification that plays a key role in adjusting chloroplast functions in response to changing light conditions. Redox-sensitive target proteins are reduced upon illumination, which turns on (or off in a certain case) their enzyme activities. A redox cascade via ferredoxin, ferredoxin-thioredoxin reductase, and thioredoxin has been classically recognized as the key system for transmitting the light-induced reductive signal to target proteins. By contrast, the molecular mechanism underlying target protein oxidation, which is observed during light to dark transitions, remains undetermined over the past several decades. Recently, the factors and pathways for protein thiol oxidation in chloroplasts have been reported, finally shedding light on this long-standing issue. We identified thioredoxin-like2 as one of the protein-oxidation factors in chloroplasts. This protein is characterized by its higher redox potential than that of canonical thioredoxin, that is more favorable for target protein oxidation. Furthermore, 2-Cys peroxiredoxin and hydrogen peroxide are also involved in the overall protein-oxidation machinery. Here we summarize the newly uncovered “dark side” of chloroplast redox regulation, giving an insight into how plants rest their photosynthetic activity at night.
Highlights
Sunlight is the primary energy for photosynthesis, but is the most variable environmental cue in plant habitats
It was recently suggested that NADPHTrx reductase C (NTRC) plays a pivotal role in keeping redox balance of 2-Cys Prx (2CP) in chloroplasts, which is critical for plant growth (Pérez-Ruiz et al, 2017; see below for details)
The in vivo function of this system was supported by the analyses of protein-oxidation dynamics in 2CP-deficient mutant plants in Arabidopsis; in these mutants, impaired oxidation of some chloroplast proteins (ATP synthase CF1-γ subunit, FBPase, SBPase, and Rubisco activase (RCA)) and prolonged reduction of TrxL2 were evident during light to dark transitions (Yoshida et al, 2018)
Summary
Sunlight is the primary energy for photosynthesis, but is the most variable environmental cue in plant habitats. Recent biochemical and physiological studies have identified the factors and pathways supporting the protein-oxidation process in chloroplasts (Ojeda et al, 2018; Vaseghi et al, 2018; Yoshida et al, 2018). In addition to the light/dark response described above, the emergence of multiple Trx isoforms is considered as another key feature of the redox-regulatory system in plant chloroplasts.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
