| 1. |
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| 2. |
- Arias, Carolina, et al.
(författare)
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Nuclear proteome analysis of Chlamydomonas with response to CO2 limitation
- 2020
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Ingår i: Algal Research. - : Elsevier. - 2211-9264. ; 46
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Tidskriftsartikel (refereegranskat)abstract
- Chlamydomonas reinhardtii is a unicellular green alga that can survive at a wide range of inorganic carbon (Ci) concentrations by regulating the activity of a CO2-concentrating mechanism (CCM) as well as other cellular functions. Under CO2 limited conditions, C. reinhardtii cells display a wide range of adaptive responses including changes in photosynthetic electron transport, mitochondria localization in the cells, the structure of the pyrenoid starch sheath, and primary metabolism. In addition to these functional and structural changes, gene and protein expression are also affected. Several physiological aspects of the CO2 response mechanism have been studied in detail. However, the regulatory components (transcription factors and transcriptional regulators) involved in this process are not fully characterized. Here we report a comprehensive analysis of the C. reinhardtii nuclear proteome using liquid chromatography electrospray ionization spectrometry (LC-ESI-MS). The study aims to identify the proteins that govern adaptation to varying CO2 concentrations in Chlamydomonas. The nuclear proteome of C. reinhardtii cells grown in the air at high (5%) and low (0.04%) CO2 concentrations were analyzed. Using this approach, we identified 1378 proteins in total, including 90 putative transcription factors and 27 transcriptional regulators. Characterization of these new regulatory components could shed light on the molecular mechanisms underlying acclimation to CO2 stress.
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| 3. |
- BORODIN, V, et al.
(författare)
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THE EFFECT OF LIGHT QUALITY ON THE INDUCTION OF EFFICIENT PHOTOSYNTHESIS UNDER LOW CO2 CONDITIONS IN CHLAMYDOMONAS-REINHARDTII AND CHLORELLA-PYRENOIDOSA
- 1994
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Ingår i: Physiologia Plantarum. - 0031-9317 .- 1399-3054. ; 92:2, s. 254-260
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Tidskriftsartikel (refereegranskat)abstract
- The effect of blue and red light on the adaptation to low CO2 conditions was studied in high-CO2 grown cultures of Chlorella pyrenoidosa (82T) and Chlamydomonas reinhardtii (137(+)) by measuring O-2 exchange under various inorganic carbon (C-i) concentrations. At equal photosynthetic photon flux density (PPFD), blue light was more favourable for adaptation in both species, compared to red light. The difference in photosynthetic oxygen evolution between cells adapted to low C-i under blue and red light was more pronounced when oxygen evolution was measured under low C-i compared to high C-i conditions. The effect of light quality on adaptation remained for several hours. The different effects caused by blue and red light was observed in C. pyrenoidosa over a wide range of PPFD with increasing differences at increasing PPFD. The maximal difference was obtained at a PPFD above 1 500 mu mol m(-2) s(-1). We found no difference in the extracellular carbonic anhydrase activity between blue- and red light adapted cells. The light quality effect recorded under C-i-limiting conditions in C. reinhardtii cells adapted to air, was only 37% less when instead of pure blue light red light containing 12.5% of blue light (similar PPFD as blue light) was used during adaptation to low carbon. This indicates that in addition to affecting photosynthesis, blue light affected a sensory system involved in algal adaptation to low C-i conditions. Since the affinity for C-i of C. pyrenoidosa and C. reinhardtii cells adapted to air under blue light was higher than that of cells adapted under red light, we suggest that induction of some component(s) of the C-i accumulating mechanism is regulated by the light quality.
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| 4. |
- Burén, Stefan, et al.
(författare)
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Importance of post-translational modifications for functionality of a chloroplast-localized carbonic anhydrase (CAH1) in Arabidopsis thaliana
- 2011
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 6:6, s. e21021-
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundThe Arabidopsis CAH1 alpha-type carbonic anhydrase is one of the few plant proteins known to be targeted to the chloroplast through the secretory pathway. CAH1 is post-translationally modified at several residues by the attachment of N-glycans, resulting in a mature protein harbouring complex-type glycans. The reason of why trafficking through this non-canonical pathway is beneficial for certain chloroplast resident proteins is not yet known. Therefore, to elucidate the significance of glycosylation in trafficking and the effect of glycosylation on the stability and function of the protein, epitope-labelled wild type and mutated versions of CAH1 were expressed in plant cells.Methodology/Principal FindingsTransient expression of mutant CAH1 with disrupted glycosylation sites showed that the protein harbours four, or in certain cases five, N-glycans. While the wild type protein trafficked through the secretory pathway to the chloroplast, the non-glycosylated protein formed aggregates and associated with the ER chaperone BiP, indicating that glycosylation of CAH1 facilitates folding and ER-export. Using cysteine mutants we also assessed the role of disulphide bridge formation in the folding and stability of CAH1. We found that a disulphide bridge between cysteines at positions 27 and 191 in the mature protein was required for correct folding of the protein. Using a mass spectrometric approach we were able to measure the enzymatic activity of CAH1 protein. Under circumstances where protein N-glycosylation is blocked in vivo, the activity of CAH1 is completely inhibited.Conclusions/SignificanceWe show for the first time the importance of post-translational modifications such as N-glycosylation and intramolecular disulphide bridge formation in folding and trafficking of a protein from the secretory pathway to the chloroplast in higher plants. Requirements for these post-translational modifications for a fully functional native protein explain the need for an alternative route to the chloroplast.
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| 5. |
- Carius, Anke B., et al.
(författare)
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Dynamic pH‐induced conformational changes of the PsbO protein in the fluctuating acidity of the thylakoid lumen
- 2019
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Ingår i: Physiologia Plantarum. - : John Wiley & Sons. - 0031-9317 .- 1399-3054. ; 166:1, s. 288-299
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Tidskriftsartikel (refereegranskat)abstract
- The PsbO protein is an essential extrinsic subunit of photosystem II, the pigment–protein complex responsible for light‐driven water splitting. Water oxidation in photosystem II supplies electrons to the photosynthetic electron transfer chain and is accompanied by proton release and oxygen evolution. While the electron transfer steps in this process are well defined and characterized, the driving forces acting on the liberated protons, their dynamics and their destiny are all largely unknown. It was suggested that PsbO undergoes proton‐induced conformational changes and forms hydrogen bond networks that ensure prompt proton removal from the catalytic site of water oxidation, i.e. the Mn4CaO5 cluster. This work reports the purification and characterization of heterologously expressed PsbO from green algae Chlamydomonas reinhardtii and two isoforms from the higher plant Solanum tuberosum (PsbO1 and PsbO2). A comparison to the spinach PsbO reveals striking similarities in intrinsic protein fluorescence and CD spectra, reflecting the near‐identical secondary structure of the proteins from algae and higher plants. Titration experiments using the hydrophobic fluorescence probe ANS revealed that eukaryotic PsbO proteins exhibit acid–base hysteresis. This hysteresis is a dynamic effect accompanied by changes in the accessibility of the protein's hydrophobic core and is not due to reversible oligomerization or unfolding of the PsbO protein. These results confirm the hypothesis that pH‐dependent dynamic behavior at physiological pH ranges is a common feature of PsbO proteins and causes reversible opening and closing of their β‐barrel domain in response to the fluctuating acidity of the thylakoid lumen.
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| 6. |
- Eriksson, M, et al.
(författare)
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Induction and regulation of expression of a low-CO2-induced mitochondrial carbonic anhydrase in Chlamydomonas reinhardtii
- 1998
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Ingår i: Plant Physiology. - 0032-0889 .- 1532-2548. ; 116:2, s. 637-641
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Tidskriftsartikel (refereegranskat)abstract
- The time course of and the influence of light intensity and light quality on the induction of a mitochondrial carbonic anhydrase (CA) in the unicellular green alga Chlamydomonas reinhardtii was characterized using western and northern blots. This CA was expressed only under low-CO2 conditions (ambient air). In asynchronously grown cells, the mRNA was detected 15 min after transfer from air containing 5% CO2 to ambient air, and the 21-kD polypeptide was detected on western blots after 1 h. When transferred back to air containing 5% CO2, the mRNA disappeared within 1 h and the polypeptide was degraded within 3 d. Photosynthesis was required for the induction in asynchronous cultures. The induction increased with light up to 500 mu mol m(-2) s(-1), where saturation occurred. In cells grown synchronously, however, expression of the mitochondrial CA was also detected in darkness. Under such conditions the expression followed a circadian rhythm, with mRNA appearing in the dark 30 min before the light was turned on. Algae left in darkness continued this rhythm for several days.
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| 7. |
- Eriksson, Mats, et al.
(författare)
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ISOLATION, PURIFICATION, AND CHARACTERIZATION OF MITOCHONDRIA FROM CHLAMYDOMONAS-REINHARDTII
- 1995
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Ingår i: Plant Physiology. - 0032-0889 .- 1532-2548. ; 107:2, s. 479-483
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Tidskriftsartikel (refereegranskat)abstract
- Mitochondria were isolated from autotrophically grown Chlamydomonas reinhardtii cell-wall-less mutant CW 92. The cells were broken by vortexing with glass beads, and the mitochondria were collected by differential centrifugation and purified on a Percoll gradient. The isolated mitochondria oxidized malate, pyruvate, succinate, NADH, and a-ketoglutarate. Respiratory control was obtained with malate (2.0) and pyruvate (2.2) but not with the other substrates. From experiments with KCN and salicylhydroxamic acid, it was estimated that the capacity of the cytochrome pathway was at least 100 nmol O-2 mg(-1) protein min(-1) and the capacity of the alternative oxidase was at least 50 nmol O-2 mg(-1) protein min(-1). A low sensitivity to oligomycin indicates some difference in the properties of the mitochondrial ATPase from Chlamydomonas as compared to higher plants.
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| 8. |
- FALK, S, et al.
(författare)
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CHANGES IN PHOTOSYSTEM-II FLUORESCENCE IN CHLAMYDOMONAS-REINHARDTII EXPOSED TO INCREASING LEVELS OF IRRADIANCE IN RELATIONSHIP TO THE PHOTOSYNTHETIC RESPONSE TO LIGHT
- 1992
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Ingår i: Photosynthesis Research. - 0166-8595 .- 1573-5079. ; 31:1, s. 31-40
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Tidskriftsartikel (refereegranskat)abstract
- The effects of a 60 min exposure to photosynthetic photon flux densities ranging from 300 to 2200-mu-mol m-2 s-1 on the photosynthetic light response curve and on PS II heterogeneity as reflected in chlorophyll a fluorescence were investigated using the unicellular green alga Chlamydomonas reinhardtii. It was established that exposure to high light acts at three different regulatory or inhibitory levels; 1) regulation occurs from 300 to 780-mu-mol m-2 s-1 where total amount of PS II centers and the shape of the light response curve is not significantly changed, 2) a first photoinhibitory range above 780 up to 1600-mu-mol m-2 s-1 where a progressive inhibition of the quantum yield and the rate of bending (convexity) of the light response curve can be related to the loss of Q(B)-reducing centers and 3) a second photoinhibitory range above 1600-mu-mol m-2 s-1 where the rate of light saturated photosynthesis also decreases and convexity reaches zero. This was related to a particularly large decrease in PS II(alpha) centers and a large increase in spill-over in energy to PS I.
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| 9. |
- FALK, S, et al.
(författare)
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RECOVERY OF PHOTOSYNTHESIS AND PHOTOSYSTEM-II FLUORESCENCE IN CHLAMYDOMONAS-REINHARDTII AFTER EXPOSURE TO 3 LEVELS OF HIGH LIGHT
- 1992
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 85:1, s. 61-68
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Tidskriftsartikel (refereegranskat)abstract
- Recovery from 60 min of photoinhibitory treatment at photosynthetic photon flux densities of 500, 1400 and 2200-mu-mol m-2 s-1 was followed in cells of the green alga Chlamydomonas reinhardtii grown at 125-mu-mol m-2 s-1. These light treatments re resent photoregulation, moderate photoinhibition and strong photoinhibition, respectively. Treatment in photoregulatory light resulted in an increased maximal rate of oxygen evolution (P(max)) and an increased quantum yield (PHI), but a 15% decrease in F(V)/F(M). Treatment at moderately photoinhibitory light resulted in a 30% decrease in F(V)/F(M) and an approximately equal decrease in PHI. Recovery in dim light restored F(V)/F(M) within 15 and 45 min after high light treatment at 500 and 1 400-mu-mol m-2 s-1 respectively. Convexity (THETA), a measure of the extent of co-limitation between PS II turnover and whole-chain electron transport, and PHI approached, but did not reach the control level during recovery after exposure to 1 400-mu-mol m 2 s-1, whereas P(max) increased above the control. Treatment at 2200-mu-mol m-2 s-1 resulted in a strong reduction of the modeled parameters PHI, THETA and P(max). Subsequent recovery was initially rapid but the rate decreased, and a complete recovery was not reached within 120 min. Based on the results, it is hypothesized that exposure to high light results in two phenomena. The first, expressed at all three light intensities, involves redistribution within the different aspects of PS II heterogeneity rather than a photoinhibitory destruction of PS II reaction centers. The second, most strongly expressed at 2200-mu-mol m-2 s-1, is a physical damage to PS II shown as an almost total loss of PS II(alpha) and PS II Q(B)-reducing centers. Thus recovery displayed two phases, the first was rapid and the only visible phase in algae exposed to 500 and 1 400-mu-mol m-2 s-1. The second phase was slow and visible only in the later part of recovery in cells exposed to 2 200-mu-mol m-2 s-1.
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| 10. |
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