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. 2022 Feb 15;60(2):212–218. doi: 10.32615/ps.2022.004

Chloroplast protease/chaperone AtDeg2 holds γ1 subunit of ATP synthase in an unaggregated state under high irradiance conditions in Arabidopsis thaliana

P Jagodzik 1, G Jackowski 1,*
PMCID: PMC11558513  PMID: 39650758

Abstract

Little data on the role played in vivo by chloroplast protein AtDeg2 as a chaperone is available. Therefore, we sought for chloroplast proteins protected from high irradiance-induced interprotein aggregation via disulphide bridges by AtDeg2 acting as a holdase. To reach this goal, we performed analyses which involved comparative diagonal electrophoreses of lysates of chloroplasts isolated from wild type (WT) plants and transgenic plants 35S:AtDEG2ΔPDZ1-GFP which expressed AtDeg2 lacking its chaperone activity but retaining the protease activity. The results of the analyses indicate that AtDeg2 acting as a holdase prevents a single chloroplast protein, i.e., the γ1 subunit of ATP synthase from long-term high irradiance-induced homodimerization mediated by disuplhide bridges and this allows us to better understand a complexity of physiological significance of AtDeg2 – the chloroplast protein of dual protease/chaperone activity.

Keywords: chaperone, Deg2, elevated irradiance, homodimerization, protease

Highlights

  • Under high light, 35S:AtDEG2ΔPDZ1-GFP plants express AtDeg2 lacking chaperone activity

  • 35S:AtDEG2ΔPDZ1-GFP and WT plants show a very similar disulphide reductase activity

  • AtDeg2 inhibits high light-induced homodimerization of γ1 subunit of ATP synthase

Introduction

Deg serine non-ATP hydrolyzing endopeptidases were first discovered in E. coli (Lipińska et al. 1988, Strauch and Beckwith 1988) and later demonstrated to be present in cells of organisms belonging to all domains of life (Ortega et al. 2009). The mature molecule of chloroplast serine endopeptidase AtDeg2 contains an N-terminal protease domain (with H159 D190 S268 triad as the catalytic site) as well as PDZ1 and PDZ2 domains shown to be involved in dimerization of trimeric units into non-active AtDeg2 hexamers, and suggested to be involved in rearrangement of trimeric units into enzymatically competent, higher oligomeric states of the protein (Sun et al. 2012). It has been shown recently that apart from being a non-ATP-hydrolyzing protease, chloroplast protein AtDeg2 owned chaperone activity as well, consisting in an ability to inhibit the aggregation of denatured lysozyme in vitro (holdase activity – Sun et al. 2012, Jagodzik et al. 2018) and to cause disaggregation of produced lysozyme aggregates (disaggregase activity – Jagodzik et al. 2018). It was demonstrated that PDZ1 and PDZ2 domains were required for both holdase and disaggregase activities of AtDeg2 in vitro and protease domain (but not S268 in its catalytic site) contributed to these activities (Jagodzik et al. 2018). However, data concerning the role played by AtDeg2 in vivo as chaperone are rather limited. Namely, we have shown recently that under non-stressing conditions, AtDeg2 influenced a few phenotypic features of Arabidopsis thaliana through its chaperone activity in conjunction with the protease activity, i.e., the time when cotyledons were fully opened, the number of inflorescence branches, and seed length in plants which have terminated their generative development (Adamiec et al. 2018). To date, no chloroplast proteins, whose potential aggregation were inhibited by AtDeg2 or proteins which form aggregates subsequently disaggregated by AtDeg2, have been identified (neither under non-stressing conditions nor any abiotic stress). To fill this gap in our understanding of the functions performed by AtDeg2 in vivo due to its chaperone activity, we sought for chloroplast proteins protected from aggregation by AtDeg2 acting as a holdase, i.e., native protein substrates for holdase activity of AtDeg2. High irradiance stress is known to induce the accumulation of reactive oxygen species in plant cells (Hideg et al. 2002, Grabsztunowicz et al. 2015) which effectively promote oxidative modifications of sulfur-containing amino acid residues (Gill and Tuteja 2010) and induction of intra- or interprotein disulphide bridges is one of the forms of oxidative modifications of cysteine residue (Davies 2004, 2005). In fact, it was shown earlier that interprotein aggregates linked by disulphide bridges in chloroplasts may be induced by other stresses, e.g., in Chlamydomonas reinhardtii cells as a result of salt stress (Marín-Navarro and Moreno 2006) and in leaves of A. thaliana plants exposed to low-irradiance stress (Grabsztunowicz et al. 2015). Since both these stresses were demonstrated to induce the accumulation of reactive oxygen species in plant cells as well (Mittler et al. 2004, Grabsztunowicz et al. 2015), we expected that under conditions of high irradiance stress, some oxidatively modified chloroplast proteins might participate in the formation of aggregates held by disulphide bridges and hypothesized that a certain pool of these proteins might be protected from the aggregation by AtDeg2. Our analyses included WT plants and transgenic plants 35S:AtDEG2ΔPDZ1-GFP that expressed AtDeg2 lacking both chaperone activities but retaining its protease activity (Adamiec et al. 2018). Our results indicate that AtDeg2 operates in vivo as holdase by inhibiting the formation of homodimers of γ1 subunit of ATP synthase in chloroplasts of plants exposed to long-term high irradiance stress.

Materials and methods

Plant material and growth conditions

For a short-term high irradiance stress, A. thaliana ecotype Columbia WT plants and eight transgenic lines 35S:AtDEG2ΔPDZ1-GFP were grown on sphagnum peat moss and wood pulp (Agro Wit, Poland) at 110 μmol(photon) m–2 s–1 (low irradiance) as described previously by Baranek et al. (2015) (except that the relative humidity was set at 70%) until the secondary stage 6.0 of ontogenesis (Boyes et al. 2001) was reached, and then the plants were transferred for 5 h to 400 μmol(photon) m–2 s–1. For a long-term stress, the plants were grown until 6.0 stage was reached under the conditions described previously by Baranek et al. (2015) with the irradiance and relative humidity set at 400 μmol(photon) m–2 s–1 and 70%, respectively.

Plasmid construction

The vector construct for stable transformation (35S:AtDEG2ΔPDZ1-GFP) was prepared and the transformation performed exactly as described previously (Adamiec et al. 2018). Stable transformants were selected on MS media supplemented with gluphosinate ammonium (10 mg L–1).

Isolation of chloroplast lysates and isolation of stromal fraction

Chloroplasts were isolated from leaves of WT plants and eight transgenic lines 35S:AtDEG2ΔPDZ1-GFP exactly as described by us previously (Grabsztunowicz and Jackowski 2013). The lysates were prepared by suspending pelleted chloroplasts in a lysis buffer (which contained 50 mM Hepes-KOH, pH 7.8, 10 mM MgCl2, and 10 mM iodoacetamide) and incubating them on ice for a few min. Chloroplast stromal fraction was prepared by subjecting chloroplast lysates to a series of differential centrifugations exactly according to Grabsztunowicz et al. (2015). The protein concentration was determined with QuickStartTM Bradford 1× Dye Reagent according to the manufacturer's recommendations (BioRad, USA).

SDS-PAGE, diagonal electrophoresis, immunoblotting, gel staining, protein quantitation and identification

Samples of chloroplast lysates containing equal amounts of protein were subjected to SDS-PAGE according to Laemmli (1970). After the electrophoresis, the polypeptides were electrotransferred on PVDF membranes and immunostained with monospecific primary antibodies (rabbit) raised against Deg2 C-terminal sequence (TQALDQGIGDSPVS) (GenScript, USA). The immunostained bands were quantitated by applying ChemiDoc Imaging System (BioRad, USA) and Gelix One 1d Software ver. 4.1 (Biostep, Germany). Three individual blots representing two biological replicates were analyzed.

Chloroplast lysates were concentrated as described by Jackowski and Przymusiński (1995) and the concentrated lysates containing 120 μg of protein were subjected to diagonal electrophoresis exactly as described by Grabsztunowicz et al. (2015). After the diagonal electrophoresis the proteins were visualized by Blue Silver method according to Candiano et al. (2004). The highest protein amount of 120 μg was the amount allowing to avoid obscuring the spots lying close to the diagonal of the gel, by the diagonal itself. Individual spots were quantitated using ChemiDoc Imaging System and PDQuest 2-D software (BioRad, USA). The spot which migrated under the diagonal of the gel and was found to be more abundant in the chloroplast lysates of 35S:AtDEG2ΔPDZ1-GFP 4.23 transformants than in WT plants was excised and the protein identified by mass spectrometry at the Institute of Biochemistry and Biophysics of Polish Academy of Sciences in Warsaw, Poland. Six individual gels representing two biological replicates were analyzed.

Disulphide reductase activity

was assayed by using insulin as a substrate as described by Holmgren (1979) with modifications introduced by Jeon and Ishikawa (2002). Briefly, bovine insulin was incubated for 30 min at 30°C in 100 mM sodium phosphate buffer, pH 7.0 containing 1 mM DTT, in the presence or in the absence of chloroplast stroma samples representing WT plants and 35S:AtDEG2ΔPDZ1-GFP transgenic line 4.23. An increase in the absorbance at 650 nm was determined (Ultrospec 4000 UV/visible spectrophotometer, Pharmacia Biotech, Sweden), which was due to the aggregation of free insulin chains produced by reduction of interchain disulphide linkages, catalyzed by those proteins of the stroma samples which possessed disulphide reductase activity (Holmgren 1979). The absorption values at 650 nm were determined by performing four enzymatic assays representing two biological replicates.

Statistical analysis

Statistical significance of the differences in the level of the appropriate proteins resolved by SDS-PAGE and diagonal electrophoresis as well as the differences in the disulphide reductase activity between the appropriate samples were analyzed with the Student's t-test at p< 0.05. Prior to the Student's t-test, the normality of data distribution was checked with the Shapiro-Wilk test and the equality of variances was determined by applying the F test (Origin, OriginLab Corporation, USA).

Results

Transgenic lines

To search for chloroplast proteins protected by AtDeg2 acting as a holdase from high irradiance-dependent interprotein aggregation via disulphide bridges, we applied 35S:AtDEG2ΔPDZ1-GFP transgenic lines (represented by T2 progeny) generated in the deg2-3 background (Luciński et al. 2011, Adamiec et al. 2018). The 35S:AtDEG2ΔPDZ1-GFP transformants express – in fusion with GFP – the mutant AtDeg2 ΔPDZ1 protein which is proteolytically active but lacks holdase and disaggregase activities (Adamiec et al. 2018). We attempted to choose the line(s) for which the abundance of AtDeg2 ΔPDZ1-GFP fusion was under high irradiance stress the most similar to that of native AtDeg2 in WT plants. For this purpose, the immunoblot-based screening of AtDeg2 level was performed in lysates of chloroplasts isolated from leaves of WT plants and eight transgenic lines exposed to short- or long-term high irradiance stress (Fig. 1). The 35S:AtDEG2ΔPDZ1-GFP 4.31 and 35S:AtDEG2ΔPDZ1-GFP 4.23 lines were used for further analyses with respect to short-term high irradiance stress and long-term high irradiance stress, respectively, as the level of AtDeg2 ΔPDZ1-GFP fusions in these lines were not significantly different from those of AtDeg2 in WT plants under specific stress conditions whereas AtDeg2 ΔPDZ1-GFP levels in remaining lines tended to be significantly reduced.

Fig. 1. Immunoblot analysis of the protein levels of AtDeg2 and AtDeg2 ΔPDZ1-GFP fusions in WT plants and eight transgenic 35S:AtDEG2ΔPDZ1-GFP lines expressing mutated version of AtDeg2 which is proteolytically active but lacks its chaperone activities. 8 μg of protein of lysates of chloroplasts isolated from leaves of plants exposed to short-term high irradiance stress (A) or long-term high irradiance stress (B) was resolved by SDS-PAGE, electrotransferred onto PVDF membrane and immunodecorated with monospecific anti-Deg2 antibodies. The numbers indicated under the lanes show signal strength of AtDeg2 or AtDeg2 ΔPDZ1-GFP fusions quantified relative to the values ±SE determined for AtDeg2 in WT plants (100%). The signals were determined by scanning three blots generated through analyses of plants exposed to short-term stress and three blots generated through analyses of plants exposed to long-term stress. For each of the stresses the three blots represented two biological replicates. The asterisks indicate the data for which any genotype/WT plants differences were significant (p<0.05).

Fig. 1

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Identification of native protein substrate for holdase activity of AtDeg2

The search for chloroplast proteins, which may be protected by AtDeg2 through its holdase activity from forming interprotein aggregates held by disulphide bridges – possibly arising as a result of exposition of plants to prolonged high irradiance stress – was accomplished by the experimental approach based on diagonal electrophoresis, i.e., a form of two-dimensional analysis useful for investigating the subunit composition of multi-subunit proteins containing interprotein disulphide bonds. The proteins that are linked by intermolecular disulphide bridges migrate below the diagonal of the gel at the second dimension. The application of diagonal electrophoresis to accomplish search for native protein substrates for holdase activity of AtDeg2 is based on a rationale that (1) AtDeg2 holdase activity in high irradiance-stressed WT plants may involve an inhibitory effect on interprotein aggregation of some oxidatively modified chloroplast proteins; (2) AtDeg2 lacking its holdase activity in high irradiance-stressed 35S:AtDEG2ΔPDZ1-GFP transformants may be fully or partially unable to inhibit interprotein aggregation of oxidatively modified chloroplast proteins.

Thus, native substrates for chaperone activity of AtDeg2 were searched for as proteins isolated from chloroplasts of leaves of 35S:AtDEG2ΔPDZ1-GFP transformants exposed to high irradiance conditions, which migrated under the diagonal of the gel after diagonal electrophoresis and were significantly more abundant than in chloroplasts of high irradiance-exposed WT plants. As shown in Fig. 2A, no proteins meeting these criteria were found in chloroplast lysates derived from 35S:AtDEG2ΔPDZ1-GFP 4.31 transformants exposed to short-term stress. However, a single protein was detected; it migrated under the diagonal of the gel (at 35 kDa) and was considerably more abundant in chloroplast lysates of the 35S:AtDEG2ΔPDZ1-GFP 4.23 transformants exposed to long-term stress compared to WT plants (306 ± 22% of the value found in lysates of WT plants; Fig. 2B). This protein was identified by mass spectrometry as the γ1 subunit of ATP synthase (score: 1,738; sequence coverage: 42%). Thus, this protein seems to be protected by AtDeg2 acting as a holdase from being aggregated via disulphide bridges in response to long-term high irradiance stress. The implicit position of the high irradiance-induced aggregates at the first dimension matched the molecular mass of the dimer of γ1 subunits (ca 70 kDa) and no other spot(s) was recorded in between the position of the monomeric γ1 subunit and the diagonal of the gel, indicating that in the absence of chaperone activity of AtDeg2 γ1 subunits of ATP synthase tended to homodimerize.

Fig. 2. Diagonal electrophoresis-based analysis of chloroplast proteins isolated from leaves of WT plants as well as 35S:AtDEG2ΔPDZ1-GFP 4.23 and 4.31 transformants. 120 μg of protein of lysates of chloroplasts isolated from leaves of WT plants and 35S:AtDEG2ΔPDZ1-GFP 4.31 transformants exposed to short-term high irradiance stress (A) or from leaves of WT plants and 35S:AtDEG2ΔPDZ1-GFP 4.23 transformants exposed to long-term high irradiance stress (B) was resolved by diagonal electrophoresis and stained according to Blue Silver method. The arrow points to the spot which migrated under the diagonal of the gel and was significantly more abundant in chloroplasts of 35S:AtDEG2ΔPDZ1-GFP 4.23 transformants than in chloroplasts of WT plants (the asterisk, p<0.05). The region of the gel adjacent to this spot was surrounded by a square and shown in enlarged form in upper right corner of the gel. The indicated signal strength ± SE of the spot in 35S:AtDEG2ΔPDZ1-GFP 4.23 transformants was quantified relative to the value determined for WT plants (100%). Six gels representing two biological replicates were scanned for each of two stresses.

Fig. 2

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To provide the validation that the γ1 subunit of ATP synthase is protected by AtDeg2 from being homodimerized via disulphide bridges in response to long-term high irradiance stress, we explored the possibility that overaccumulation of this subunit in chloroplast lysates of 35SAtDEG2ΔPDZ1-GFP 4.23 transformants occurred rather due to lower efficiency of reduction of disulphide bonds in their chloroplasts vs. chloroplasts of WT plants. To prove so, we determined the insulin-targeted disulphide reductase activity of chloroplasts of both genotypes.

Specifically, stroma samples of plants representing both genotypes were analyzed since the reduction of intra- and interprotein disulphide bonds is catalyzed by thiol oxidoreductases (belonging to thioredoxin and glutaredoxin families) which are located in stroma (Rouhier 2010, Nikkanen and Rintamäki 2014). As shown in Fig. 3, stroma samples collected from chloroplasts of WT plants and the transformants exhibited a very similar insulin reduction activity. This finding strongly validates the results of the analyses based on diagonal electrophoresis. Namely, it indicates that the γ1 subunit of ATP synthase is a substrate for AtDeg2 holdase chaperone activity. AtDeg2 acts in such a way as to protect γ1 subunit from homodimerization under high irradiance conditions.

Fig. 3. Disulphide reduction activity in chloroplasts isolated from leaves of WT plants and 35S:AtDEG2ΔPDZ1-GFP 4.23 transformants. The DTT-dependent insulin reduction by stroma samples of chloroplasts isolated from leaves of WT plants and 35S:AtDEG2ΔPDZ1-GFP 4.23 transformants which were exposed to long-term high irradiance stress was recorded as the increase in light absorption at 650 nm due to light scattering by aggregates of free insulin polypeptide chains in the assays containing 0 or 5 μg of the stroma protein. The values A650 ± SE indicate the percentages of absorption signal at 650 nm identified at time point 30 min in the assays containing stroma samples relative to value determined in the assay without stroma samples (100%). The asterisks indicate the data for which the differences between A650 values in assays involving stroma samples and the assay without stroma samples were significant (p<0.05). The absorption values at 650 nm were determined by performing four enzymatic assays representing two biological replicates.

Fig. 3

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Discussion

There are indications that some abiotic stresses known to enhance the production of reactive oxygen species may induce interprotein aggregation via disulphide bridges in chloroplasts (Mittler et al. 2004, Marín-Navarro and Moreno 2006, Grabsztunowicz et al. 2015). No direct data was reported to date demonstrating that this effect can be induced by high irradiance stress as well, even though this stress is also known to stimulate the accumulation of reactive oxygen species (Hideg et al. 2002, Grabsztunowicz et al. 2015). Our results of the studies based on diagonal electrophoresis allowed us to conclude that γ1 subunits of ATP synthase could homodimerize in chloroplasts of WT plants grown under high-irradiance conditions and that the homodimers were kept by disulphide bridges (Fig. 2). It was revealed that cysteine sulfenic acid might play an important role as an oxidized sulfur intermediate in disulphide-based dimerization of protein molecules containing free cysteine residues (Rehder and Borges 2010) and the cysteine sulfenic acid-containing non-native protein intermediates may recruit chaperones with holdase activity to inhibit the productive protein dimerization to occur. Our results indicate that in chloroplasts of WT plants exposed to long-term high irradiance stress homodimers of γ1 subunits of ATP synthase were more than three times less abundant compared to chloroplasts isolated from leaves of the 35S:AtDEG2ΔPDZ1-GFP 4.23 transformants which express – in fusion with GFP – AtDeg2 version lacking both chaperone activities (Fig. 2). Since AtDeg2 ΔPDZ1 protein was proteolytically active (Jagodzik et al. 2018), the overaccumulation of homodimers of γ1 subunits of ATP synthase in the transformants' chloroplasts could not be ascribed to the reduction in efficiency of hypothetical AtDeg2-dependent degradation of the homodimers. As the total disulphide reductase activity detected in stroma samples of chloroplasts isolated from the leaves of both genotypes was very similar (Fig. 3), the homodimers might be repaired by reduction of disulphide bridges with the same efficiency no matter which genotype is considered. Thus, our data indicate that AtDeg2 inhibits in vivo the formation of homodimers of γ1 subunit of ATP synthase in chloroplasts of Arabidopsis plants exposed to long-term high irradiance stress.

The chloroplast ATP synthase (cF1F0) uses the proton motive force generated across the thylakoid membrane to drive ATP synthesis from ADP and Pi by rotary catalysis (Junesch and Gräber 1987). It has been known for some time that in plants and green algae chloroplasts, ATP synthase catalytic activity is regulated by thiol modulation of the γ subunit. In the dark, an intrapeptide disulphide bond is formed between two redox-active cysteine residues resulting in ATP synthase inactivation and in the light, ATP synthase is activated via reduction of the disulphide bond catalyzed by reduced thioredoxin-f (Arana and Vallejos 1982, Nalin and McCarty 1984). In A. thaliana, the classical light/dark redox regulation applies only to γ1 subunit (Kohzuma et al. 2012), one of the two homologues of the regulatory subunit coded by two individual genes located in nuclear genome of this species (Inohara et al. 1991). These are Cys199 and Cys205 residues of the γ1 subunit which are thought to be linked by a disulphide bridge in the dark while Cys89 apparently is not involved (Nalin and McCarty 1984). It may be proposed that exposition to high irradiance results in the formation of non-native interprotein disulphide bridges between those Cys residues which are located in the stroma-exposed shaft of the central rotor of the ATP synthase particle (Cys199, Cys205, and, possibly, Cys89). ATP synthase particles are confined to end grana membranes and stroma lamellae (Daum et al. 2010) and AtDeg2 was found to be associated exclusively with the stromal side of non-appressed thylakoid membranes, i.e., stroma lamellae, grana margins, and end membranes (Haußühl et al. 2001). Since 15% of ATP synthase particles cover stromal side of these membranes in the form of random assemblies of two or more copies (Daum et al. 2010), it seems plausible that the monomers included in the assemblies may establish contacts close enough for γ1 – γ1 intersubunit non-native disulphide bridges to be formed under oxidizing conditions. A certain population of the sulfenic acid-containing non-native γ1 intermediates can be recognized and held by AtDeg2 until sulfenic acid becomes reduced by thioredoxin or reacts with GSH to generate a mixed disulfide, later reduced by glutaredoxin (Lo Conte and Carroll 2013). Alternatively, it may be hypothesized that homodimerization of γ1 subunits via disulphide bridges takes place in the stroma during the assembly of CF1 portion of ATP synthase, before folded γ1 subunits get associated with α3β3 hexamer to yield an active CF1 core (Chen and Jagendorf 1994, Mao et al. 2015) and that all three Cys residues (Cys89, Cys199, Cys205) could be engaged.

Unexpectedly, no chloroplast proteins were found to be protected by AtDeg2 from being aggregated via disuplhide bridges under short-term high irradiance stress. One possible explanation is that AtDeg2 pool in WT plants shifted for 5 h to high irradiance is not large enough to exert a detectable holdase activity. This suggestion is supported by the observation that AtDEG2 was downregulated about twofold over such treatment (Adamiec et al. 2011).

Acknowledgements

This work was supported by the Polish National Science Center based on the decision number DEC-2013/09/B/NZ3/00449.

Abbreviations

DTT

dithiothreitol

GFP

green fluorescent protein

GSH

reduced glutathione

SDS-PAGE

sodium dodecylsulphate polyacrylamide gel electrophoresis

Conflict of interest

The authors declare that they have no conflict of interest.

References

  1. Adamiec M., Jagodzik P., Wyka T.P. et al. : Chloroplast protease/chaperone AtDeg2 influences cotyledons opening and reproductive development in Arabidopsis. – Acta Soc. Bot. Pol. 87: 3584, 2018. https://pbsociety.org.pl/journals/index.php/asbp/article/view/asbp.3584 [Google Scholar]
  2. Adamiec M., Luciński R., Jackowski G.: The irradiance dependent transcriptional regulation of AtCLPB3 expression. – Plant Sci. 181: 449-456, 2011. https://www.sciencedirect.com/science/article/pii/S0168945211002068?via%3Dihub [DOI] [PubMed] [Google Scholar]
  3. Arana J.L., Vallejos R.H.: Involvement of sulfhydryl groups in the activation mechanism of the ATPase activity of chloroplast coupling factor 1. – J. Biol. Chem. 257: 1125-1127, 1982. https://www.sciencedirect.com/science/article/pii/S0021925819681597?via%3Dihub [PubMed] [Google Scholar]
  4. Baranek M., Wyka T.P., Jackowski G.: Downregulation of chloroplast protease AtDeg5 leads to changes in chronological progression of ontogenetic stages, leaf morphology and chloroplast ultrastructure in Arabidopsis. – Acta Soc. Bot. Pol. 84: 59-70, 2015. https://pbsociety.org.pl/journals/index.php/asbp/article/view/asbp.2015.001 [Google Scholar]
  5. Boyes D.C., Zayed A.M., Ascenzi R. et al. : Growth stage-based phenotypic analysis of Arabidopsis: a model for high throughput functional genomics in plants. – Plant Cell 13: 1499-1510, 2001. https://academic.oup.com/plcell/article/13/7/1499/6009554 [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Candiano G., Bruschi M., Musante L. et al. : Blue silver: a very sensitive colloidal Coomassie G-250 staining for proteome analysis. – Electrophoresis 25: 1327-1333, 2004. https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/elps.200305844 [DOI] [PubMed] [Google Scholar]
  7. Chen G.G., Jagendorf A.T.: Chloroplast molecular chaperone-assisted refolding and reconstitution of an active multisubunit coupling factor CF1 core. – P. Natl. Acad. Sci. USA 91: 11497-11501, 1994. https://www.pnas.org/content/91/24/11497 [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Daum B., Nicastro D., Austin J. II. et al. : Arrangement of photosystem II and ATP synthase in chloroplast membranes of spinach and pea. – Plant Cell 22: 1299-1312, 2010. https://academic.oup.com/plcell/article/22/4/1299/6096987 [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Davies M.J.: Reactive species formed on proteins exposed to singlet oxygen. – Photoch. Photobio. Sci. 3: 17-25, 2004. https://pubs.rsc.org/en/content/articlelanding/2004/PP/b307576c [DOI] [PubMed] [Google Scholar]
  10. Davies M.J.: The oxidative environment and protein damage. – BBA-Proteins Proteom. 1703: 93-109, 2005. https://www.sciencedirect.com/science/article/pii/S1570963904002183?via%3Dihub [DOI] [PubMed] [Google Scholar]
  11. Gill S.S., Tuteja N.: Reactive oxygen species and antioxidant machinery in abiotic stress tolerance in crop plants. – Plant Physiol. Bioch. 48: 909-930, 2010. https://www.sciencedirect.com/science/article/pii/S0981942810001798?via%3Dihub [DOI] [PubMed] [Google Scholar]
  12. Grabsztunowicz M., Górski Z., Luciński R., Jackowski G.: A reversible decrease in ribulose 1,5-bisphosphate carboxylase/oxygenase carboxylation activity caused by the aggregation of the enzyme’s large subunit is triggered in response to the exposure of moderate irradiance-grown plants to low irradiance. – Physiol. Plantarum 154: 591-608, 2015. https://onlinelibrary.wiley.com/doi/10.1111/ppl.12322 [DOI] [PubMed] [Google Scholar]
  13. Grabsztunowicz M., Jackowski G.: Isolation of intact and pure chloroplasts from leaves of Arabidopsis thaliana plants acclimated to low irradiance for studies on Rubisco regulation. – Acta Soc. Bot. Pol. 82: 91-95, 2013. https://pbsociety.org.pl/journals/index.php/asbp/article/view/asbp.2012.043 [Google Scholar]
  14. Haußühl K., Andersson B., Adamska I.: A chloroplast DegP2 protease performs the primary cleavage of the photodamaged D1 protein in plant photosystem II. – EMBO J. 20: 713-722, 2001. https://www.embopress.org/doi/full/10.1093/emboj/20.4.713 [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Hideg É., Barta C., Kálai T. et al. : Detection of singlet oxygen and superoxide with fluorescence sensors in leaves under stress by photoinhibition or UV radiation. – Plant Cell Physiol. l43: 1154-1164, 2002. https://academic.oup.com/pcp/article/43/10/1154/1849368 [DOI] [PubMed] [Google Scholar]
  16. Holmgren A.: Thioredoxin catalyzes the reduction of insulin disulfides by dithiothreitol and dihydrolipoamide. – J. Biol. Chem. 254: 9627-9632, 1979. https://www.sciencedirect.com/science/article/pii/S0021925819835627?via%3Dihub [PubMed] [Google Scholar]
  17. Inohara N., Iwamoto A., Moriyama Y. et al. : Two genes, atpC1 and atpC2, for the γ subunit of Arabidopsis thaliana chloroplast ATP synthase. – J. Biol. Chem. 25: 7333-7338, 1991. https://www.jbc.org/article/S0021-9258(20)89450-2/fulltext [PubMed] [Google Scholar]
  18. Jackowski G., Przymusiński R.: The resolution and biochemical characterization of subcomplexes of the main light-harvesting chlorophyll a/b-protein complex of photosystem II (LHCII). – Photosynth. Res. 43: 41-48, 1995. https://link.springer.com/article/10.1007/BF00029461 [DOI] [PubMed] [Google Scholar]
  19. Jagodzik P., Luciński R., Misztal L., Jackowski G.: The contribution of individual domains of chloroplast protein AtDeg2 to its chaperone and proteolytic activities. – Acta Soc. Bot. Pol. 87: 3570, 2018. https://pbsociety.org.pl/journals/index.php/asbp/article/view/asbp.3570 [Google Scholar]
  20. Jeon S.-J., Ishikawa K.: Identification and characterization of thioredoxin and thioredoxin reductase from Aeropyrum pernix K1. – Eur. J. Biochem. 269: 5423-5430, 2002. https://febs.onlinelibrary.wiley.com/doi/full/10.1046/j.1432-1033.2002.03231.x [DOI] [PubMed] [Google Scholar]
  21. Junesch U., Gräber P.: Influence of the redox state and the activation of the chloroplast ATP synthase on proton-transport-coupled ATP synthesis/hydrolysis. – BBA-Bioenergetics 893: 275-288, 1987. https://www.sciencedirect.com/science/article/pii/0005272887900491 [Google Scholar]
  22. Kohzuma K., Dal Bosco C., Kanazawa A. et al. : Thioredoxin-insensitive plastid ATP synthase that performs moonlighting functions. – P. Natl. Acad. Sci. USA 109: 3293-3298, 2012. https://www.pnas.org/content/109/9/3293 [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Laemmli U.K.: Cleavage of structural proteins during the assembly of the head of bacteriophage T4. – Nature 227: 680-685, 1970. [DOI] [PubMed] [Google Scholar]
  24. Lipińska B., King J., Ang D., Georgopoulos C.: Sequence analysis and transcriptional regulation of the Escherichia coli grpE gene, encoding a heat shock protein. – Nucleic Acids Res. 16: 7545-7562, 1988. https://academic.oup.com/nar/article/16/15/7545/1073466 [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Lo Conte M., Carroll K.S.: The redox biochemistry and protein sulfenylation and sulfinylation. – J. Biol.Chem. 288: 26480-26488, 2013. https://www.sciencedirect.com/science/article/pii/S0021925820490532?via%3Dihub [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Luciński R., Misztal L., Samardakiewicz S., Jackowski G.: The thylakoid protease Deg2 is involved in stress-related degradation of photosystem II light-harvesting protein Lhcb6 in Arabidopsis thaliana. – New Phytol. 192: 74-86, 2011. https://nph.onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2011.03782.x [DOI] [PubMed] [Google Scholar]
  27. Mao J., Chi W., Ouyang M. et al. : PAB is an assembly chaperone that functions downstream of chaperonin 60 in the assembly of chloroplast ATP synthase coupling factor 1. – P. Natl. Acad. Sci. USA 112: 4152-4157, 2015. https://www.pnas.org/content/112/13/4152 [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Marín-Navarro J., Moreno J.: Cysteines 449 and 459 modulate the reduction–oxidation conformational changes of ribulose-1,5-bisphosphate carboxylase/oxygenase and the translocation of the enzyme to membranes during stress. – Plant Cell Environ. 29: 898-908, 2006. https://onlinelibrary.wiley.com/doi/10.1111/j.1365-3040.2005.01469.x [DOI] [PubMed] [Google Scholar]
  29. Mittler R., Vanderauwera S., Gollery M., Van Breugesem F.: Reactive oxygen gene network in plants. – Trends Plant Sci. 9: 490-498, 2004. https://www.sciencedirect.com/science/article/pii/S1360138504002043?via%3Dihub [DOI] [PubMed] [Google Scholar]
  30. Nalin C.M., McCarty R.E.: Role of disulfide bond in the gamma subunit in activation of the ATP chloroplast coupling factor 1. – J. Biol. Chem. 259: 7275-7280, 1984. https://www.sciencedirect.com/science/article/pii/S002192581739868X?via%3Dihub [PubMed] [Google Scholar]
  31. Nikkanen L., Rintamäki E.: Thioredoxin-dependent regulatory networks in chloroplasts under fluctuating light conditions. – Philos. T. Roy. Soc. B 369: 20130224, 2014. https://royalsocietypublishing.org/doi/10.1098/rstb.2013.0224 [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Ortega J., Iwańczyk J., Jomaa A.: Escherichia coli DegP: a structure-driven functional model. – J. Bacteriol. 191: 4705-4713, 2009. https://journals.asm.org/doi/10.1128/JB.00472-09 [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Rehder D.S., Borges C.R.: Cysteine sulfenic acid as an intermediate in disulfide bond formation and nonenzymatic protein folding. – Biochemistry 49: 7748-7755, 2010. https://pubs.acs.org/doi/10.1021/bi1008694 [DOI] [PMC free article] [PubMed] [Google Scholar]
  34. Rouhier N.: Plant glutaredoxins: pivotal players in redox biology and iron–sulphur centre assembly. – New Phytol. 186: 365-372, 2010. https://nph.onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2009.03146.x [DOI] [PubMed] [Google Scholar]
  35. Strauch K.L., Beckwith J.: An Escherichia coli mutation preventing degradation of abnormal periplasmic proteins. – P. Natl. Acad. Sci. USA 85: 1576-1580, 1988. https://www.pnas.org/content/85/5/1576 [DOI] [PMC free article] [PubMed] [Google Scholar]
  36. Sun R., Fan H., Gao F. et al. : Crystal structure of Arabidopsis Deg2 protein reveals an internal PDZ ligand locking the hexameric resting state. – J. Biol. Chem. 287: 37564-37569, 2012. https://www.sciencedirect.com/science/article/pii/S0021925820625509?via%3Dihub [DOI] [PMC free article] [PubMed] [Google Scholar]

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