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Chloroplasts require glutathione reductase to balance reactive oxygen species and maintain efficient photosynthesis
Author(s) -
MüllerSchüssele Stefanie J.,
Wang Ren,
Gütle Desirée D.,
Romer Jill,
RodriguezFranco Marta,
Scholz Martin,
Buchert Felix,
Lüth Volker M.,
Kopriva Stanislav,
Dörmann Peter,
Schwarzländer Markus,
Reski Ralf,
Hippler Michael,
Meyer Andreas J.
Publication year - 2020
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.14791
Subject(s) - glutaredoxin , thioredoxin , glutathione , biology , chloroplast , thioredoxin reductase , biochemistry , glutathione reductase , reactive oxygen species , chloroplast stroma , arabidopsis thaliana , microbiology and biotechnology , photosynthesis , mutant , oxidative stress , thylakoid , glutathione peroxidase , enzyme , gene
Summary Thiol‐based redox‐regulation is vital for coordinating chloroplast functions depending on illumination and has been throroughly investigated for thioredoxin‐dependent processes. In parallel, glutathione reductase (GR) maintains a highly reduced glutathione pool, enabling glutathione‐mediated redox buffering. Yet, how the redox cascades of the thioredoxin and glutathione redox machineries integrate metabolic regulation and detoxification of reactive oxygen species remains largely unresolved because null mutants of plastid/mitochondrial GR are embryo‐lethal in Arabidopsis thaliana . To investigate whether maintaining a highly reducing stromal glutathione redox potential ( E GSH ) via GR is necessary for functional photosynthesis and plant growth, we created knockout lines of the homologous enzyme in the model moss Physcomitrella patens . In these viable mutant lines, we found decreasing photosynthetic performance and plant growth with increasing light intensities, whereas ascorbate and zeaxanthin/antheraxanthin levels were elevated. By in vivo monitoring stromal E GSH dynamics, we show that stromal E GSH is highly reducing in wild‐type and clearly responsive to light, whereas an absence of GR leads to a partial glutathione oxidation, which is not rescued by light. By metabolic labelling, we reveal changing protein abundances in the GR knockout plants, pinpointing the adjustment of chloroplast proteostasis and the induction of plastid protein repair and degradation machineries. Our results indicate that the plastid thioredoxin system is not a functional backup for the plastid glutathione redox systems, whereas GR plays a critical role in maintaining efficient photosynthesis.