Possible compensatory role among chloroplast proteases under excess-light stress condition

Kato, Yusuke; Sakamoto, Wataru

doi:10.4161/psb.23198

Cited by 3 publications

(3 citation statements)

References 23 publications

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“…Chloroplasts are known to contain a number of proteases; some are localized in the stroma, whereas others, such as the FtsH and the Deg proteases, are associated with the thylakoid membranes and involved in the PSII photorepair cycle (Kato and Sakamoto, 2013). Recent results indicate that in the Arabidopsis var2 mutant deficient in FtsH2, ClpP1 is upregulated and a portion of this protease is relocalized from the stroma to the thylakoid membranes, suggesting compensation for the limitation in FtsH (Kato et al, 2012).…”

Section: Loss Of Clpp1 Leads To Increased Accumulation Of the Thylakomentioning

confidence: 99%

Conditional Depletion of the Chlamydomonas Chloroplast ClpP Protease Activates Nuclear Genes Involved in Autophagy and Plastid Protein Quality Control

et al. 2014

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Plastid protein homeostasis is critical during chloroplast biogenesis and responses to changes in environmental conditions. Proteases and molecular chaperones involved in plastid protein quality control are encoded by the nucleus except for the catalytic subunit of ClpP, an evolutionarily conserved serine protease. Unlike its Escherichia coli ortholog, this chloroplast protease is essential for cell viability. To study its function, we used a recently developed system of repressible chloroplast gene expression in the alga Chlamydomonas reinhardtii. Using this repressible system, we have shown that a selective gradual depletion of ClpP leads to alteration of chloroplast morphology, causes formation of vesicles, and induces extensive cytoplasmic vacuolization that is reminiscent of autophagy. Analysis of the transcriptome and proteome during ClpP depletion revealed a set of proteins that are more abundant at the protein level, but not at the RNA level. These proteins may comprise some of the ClpP substrates. Moreover, the specific increase in accumulation, both at the RNA and protein level, of small heat shock proteins, chaperones, proteases, and proteins involved in thylakoid maintenance upon perturbation of plastid protein homeostasis suggests the existence of a chloroplast-to-nucleus signaling pathway involved in organelle quality control. We suggest that this represents a chloroplast unfolded protein response that is conceptually similar to that observed in the endoplasmic reticulum and in mitochondria.

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Section: Loss Of Clpp1 Leads To Increased Accumulation Of the Thylakomentioning

confidence: 99%

Conditional Depletion of the Chlamydomonas Chloroplast ClpP Protease Activates Nuclear Genes Involved in Autophagy and Plastid Protein Quality Control

et al. 2014

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“…Under photoinhibitory conditions, Deg is activated to accelerate its endopeptidic cleavage of D1, resulting in an increase in D1 fragments, the N‐ or C‐termini of which can be recognized by FtsH for additional degradation. In addition to Deg, other proteases such as Clp and SppA might be involved in this alternative pathway because these were shown to be upregulated in the var2 background (under conditions in which FtsH activity is limited) and in the wild type under chronic light‐stress conditions (Kato et al ., ; Kato and Sakamoto, ). Our data showing increased D1 cleaved fragments in var2 stn8 mutants (Figure ) can be explained by the inference that degradation of D1 by Deg was somehow activated without D1 phosphorylation.…”

Section: Discussionmentioning

confidence: 98%

Phosphorylation of photosystem II core proteins prevents undesirable cleavage of D1 and contributes to the fine‐tuned repair of photosystem II

Kato

Sakamoto

2014

The Plant Journal

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SUMMARYPhotosystem II (PSII) is a primary target for light-induced damage in photosynthetic protein complexes. To avoid photoinhibition, chloroplasts have evolved a repair cycle with efficient degradation of the PSII reaction center protein, D1, by the proteases FtsH and Deg. Earlier reports have described that phosphorylated D1 is a poor substrate for proteolysis, suggesting a mechanistic role for protein phosphorylation in PSII quality control, but its precise role remains elusive. STN8, a protein kinase, plays a central role in this phosphorylation process. To elucidate the relationship between phosphorylation of D1 and the protease function we assessed in this study the involvement of STN8, using Arabidopsis thaliana mutants lacking FtsH2 [yellow variegated2 (var2)] and Deg5/Deg8 (deg5 deg8). In support of our presumption we found that phosphorylation of D1 increased more in var2. Furthermore, the coexistence of var2 and stn8 was shown to recover the delay in degradation of D1, resulting in mitigation of the high vulnerability to photoinhibition of var2. Partial D1 cleavage fragments that depended on Deg proteases tended to increase, with concomitant accumulation of reactive oxygen species in the mutants lacking STN8. We inferred that the accelerated degradation of D1 in var2 stn8 presents a tradeoff in that it improved the repair of PSII but simultaneously enhanced oxidative stress. Together, these results suggest that PSII core phosphorylation prevents undesirable cleavage of D1 by Deg proteases, which causes cytotoxicity, thereby balancing efficient linear electron flow and photo-oxidative damage. We propose that PSII core phosphorylation contributes to fine-tuned degradation of D1.

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“…For example, FtsH and Deg proteases coordinately control the turnover of D1 protein of photosystem II under high light stress. [30][31][32][33][34] While disruption of Clp protease activity is known trigger the accumulation of chaperones, likely to deal with the accumulation of misfolded or aggregated proteins that cannot be degraded (the so called unfolded protein response), a role for this complex on stress protection had not been experimentally demonstrated. Besides providing evidence of such a role, our results further suggest the existence of delivery pathways for Clp protein clients that are distinct from those already reported in the literature.…”

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confidence: 99%

Both Hsp70 chaperone and Clp protease plastidial systems are required for protection against oxidative stress

Pulido

Llamas

Rodríguez‐Concepción

2017

Plant Signaling & Behavior

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Environmental stress conditions such as high light, extreme temperatures, salinity or drought trigger oxidative stress and eventually protein misfolding in plants. In chloroplasts, chaperone systems refold proteins after stress, while proteases degrade misfolded and aggregated proteins that cannot be refolded. We observed that reduced activity of chloroplast Hsp70 chaperone or Clp protease systems both prevented growth of Arabidopsis thaliana seedlings after treatment with the oxidative agent methyl viologen. Besides showing a role for these particular protein quality control components on the protection against oxidative stress, we provide evidence supporting the existence of a yet undiscovered pathway for Clp-mediated degradation of the damaged proteins.

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Possible compensatory role among chloroplast proteases under excess-light stress condition

Cited by 3 publications

References 23 publications

Conditional Depletion of the Chlamydomonas Chloroplast ClpP Protease Activates Nuclear Genes Involved in Autophagy and Plastid Protein Quality Control

Conditional Depletion of the Chlamydomonas Chloroplast ClpP Protease Activates Nuclear Genes Involved in Autophagy and Plastid Protein Quality Control

Phosphorylation of photosystem II core proteins prevents undesirable cleavage of D1 and contributes to the fine‐tuned repair of photosystem II

Both Hsp70 chaperone and Clp protease plastidial systems are required for protection against oxidative stress

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