scholarly journals Inactivation of Genes Encoding Plastoglobulin-Like Proteins in Synechocystis sp. PCC 6803 Leads to a Light-Sensitive Phenotype

2010 ◽  
Vol 192 (6) ◽  
pp. 1700-1709 ◽  
Author(s):  
Francis X. Cunningham ◽  
Ashley B. Tice ◽  
Christina Pham ◽  
Elisabeth Gantt
Keyword(s):  
Inclusion Bodies ◽  
Light Stress ◽  
High Irradiance ◽  
Oxygenic Photosynthesis ◽  
Wild Type ◽  
Fundamental Function ◽  
Low Light ◽  
Photooxidative Damage ◽  
Genes Encoding ◽  
Pcc 6803

ABSTRACT Plastoglobulins (PGL) are the predominant proteins of lipid globules in the plastids of flowering plants. Genes encoding proteins similar to plant PGL are also present in algae and cyanobacteria but in no other organisms, suggesting an important role for these proteins in oxygenic photosynthesis. To gain an understanding of the core and fundamental function of PGL, the two genes that encode PGL-like polypeptides in the cyanobacterium Synechocystis sp. PCC 6803 (pgl1 and pgl2) were inactivated individually and in combination. The resulting mutants were able to grow under photoautotrophic conditions, dividing at rates that were comparable to that of the wild-type (WT) under low-light (LL) conditions (10 microeinsteins·m−2·s−1) but lower than that of the WT under moderately high-irradiance (HL) conditions (150 microeinsteins·m−2·s−1). Under HL, each Δpgl mutant had less chlorophyll, a lower photosystem I (PSI)/PSII ratio, more carotenoid per unit of chlorophyll, and very much more myxoxanthophyll (a carotenoid symptomatic of high light stress) per unit of chlorophyll than the WT. Large, heterogeneous inclusion bodies were observed in cells of mutants inactivated in pgl2 or both pgl2 and pgl1 under both LL and HL conditions. The mutant inactivated in both pgl genes was especially sensitive to the light environment, with alterations in pigmentation, heterogeneous inclusion bodies, and a lower PSI/PSII ratio than the WT even for cultures grown under LL conditions. The WT cultures grown under HL contained 2- to 3-fold more PGL1 and PGL2 per cell than cultures grown under LL conditions. These and other observations led us to conclude that the PGL-like polypeptides of Synechocystis play similar but not identical roles in some process relevant to the repair of photooxidative damage.

Does Astaxanthin Protect Haematococcus against Light Damage?

1998 ◽  
Vol 53 (1-2) ◽  
pp. 93-100 ◽  
Author(s):  
Lu Fan ◽  
Avigad Vonshak ◽  
Aliza Zarka ◽  
Sammy Boussiba
Keyword(s):  
Light Intensity ◽  
Light Stress ◽  
Phosphate Starvation ◽  
High Light Intensity ◽  
High Irradiance ◽  
High Light ◽  
Protective Agent ◽  
Light Damage ◽  
Low Light ◽  
Very High

Abstract The photoprotective function of the ketocarotenoid astaxanthin in Haematococcus was questioned. When exposed to high irradiance and/or nutritional stress, green Haematococcus cells turned red due to accumulation of an immense quantity of the red pigment astaxanthin. Our results demonstrate that: 1) The addition of diphenylamine, an inhibitor of astaxanthin biosynthesis, causes cell death under high light intensity; 2) Red cells are susceptible to high light stress to the same extent or even higher then green ones upon exposure to a very high light intensity (4000 μmol photon m-2 s-1); 3) Addition of 1O2 generators (methylene blue, rose bengal) under noninductive conditions (low light of 100 (μmol photon m-2 s-1) induced astaxanthin accumulation. This can be reversed by an exogenous 1O2 quencher (histidine); 4) Histidine can prevent the accumulation of astaxanthin induced by phosphate starvation. We suggest that: 1) Astaxanthin is the result of the photoprotection process rather than the protective agent; 2) 1O2 is involved indirectly in astaxanthin accumulation process.

scholarly journals Coordinated High-Light Response of Genes Encoding Subunits of Photosystem I Is Achieved by AT-Rich Upstream Sequences in the Cyanobacterium Synechocystis sp. Strain PCC 6803

2007 ◽  
Vol 189 (7) ◽  
pp. 2750-2758 ◽  
Author(s):  
Masayuki Muramatsu ◽  
Yukako Hihara
Keyword(s):  
Photosystem I ◽  
Promoter Region ◽  
Promoter Activity ◽  
Light Response ◽  
High Light ◽  
Light Conditions ◽  
Low Light ◽  
Genes Encoding ◽  
Responsive Element ◽  
Pcc 6803

ABSTRACT Genes encoding subunits of photosystem I (PSI genes) in the cyanobacterium Synechocystis sp. strain PCC 6803 are actively transcribed under low-light conditions, whereas their transcription is coordinately and rapidly down-regulated upon the shift to high-light conditions. In order to identify the molecular mechanism of the coordinated high-light response, we searched for common light-responsive elements in the promoter region of PSI genes. First, the precise architecture of the psaD promoter was determined and compared with the previously identified structure of the psaAB promoter. One of two promoters of the psaAB genes (P1) and of the psaD gene (P2) possessed an AT-rich light-responsive element located just upstream of the basal promoter region. These sequences enhanced the basal promoter activity under low-light conditions, and their activity was transiently suppressed upon the shift to high-light conditions. Subsequent analysis of psaC, psaE, psaK1, and psaLI promoters revealed that their light response was also achieved by AT-rich sequences located at the −70 to −46 region. These results clearly show that AT-rich upstream elements are responsible for the coordinated high-light response of PSI genes dispersed throughout Synechocystis genome.

scholarly journals CpcM Posttranslationally Methylates Asparagine-71/72 of Phycobiliprotein Beta Subunits in Synechococcus sp. Strain PCC 7002 and Synechocystis sp. Strain PCC 6803

2008 ◽  
Vol 190 (14) ◽  
pp. 4808-4817 ◽  
Author(s):  
Gaozhong Shen ◽  
Heidi S. Leonard ◽  
Wendy M. Schluchter ◽  
Donald A. Bryant
Keyword(s):  
Light Stress ◽  
Fluorescence Emission ◽  
High Light ◽  
State Transitions ◽  
Comparative Genomic ◽  
Beta Subunits ◽  
Wild Type ◽  
Light Harvesting Complexes ◽  
Type Strains ◽  
Pcc 6803

ABSTRACT Cyanobacteria produce phycobilisomes, which are macromolecular light-harvesting complexes mostly assembled from phycobiliproteins. Phycobiliprotein beta subunits contain a highly conserved γ-N-methylasparagine residue, which results from the posttranslational modification of Asn71/72. Through comparative genomic analyses, we identified a gene, denoted cpcM, that (i) encodes a protein with sequence similarity to other S-adenosylmethionine-dependent methyltransferases, (ii) is found in all sequenced cyanobacterial genomes, and (iii) often occurs near genes encoding phycobiliproteins in cyanobacterial genomes. The cpcM genes of Synechococcus sp. strain PCC 7002 and Synechocystis sp. strain PCC 6803 were insertionally inactivated. Mass spectrometric analyses of phycobiliproteins isolated from the mutants confirmed that the CpcB, ApcB, and ApcF were 14 Da lighter than their wild-type counterparts. Trypsin digestion and mass analyses of phycobiliproteins isolated from the mutants showed that tryptic peptides from phycocyanin that included Asn72 were also 14 Da lighter than the equivalent peptides from wild-type strains. Thus, CpcM is the methyltransferase that modifies the amide nitrogen of Asn71/72 of CpcB, ApcB, and ApcF. When cells were grown at low light intensity, the cpcM mutants were phenotypically similar to the wild-type strains. However, the mutants were sensitive to high-light stress, and the cpcM mutant of Synechocystis sp. strain PCC 6803 was unable to grow at moderately high light intensities. Fluorescence emission measurements showed that the ability to perform state transitions was impaired in the cpcM mutants and suggested that energy transfer from phycobiliproteins to the photosystems was also less efficient. The possible functions of asparagine N methylation of phycobiliproteins are discussed.

scholarly journals Signal Transduction Protein PII Phosphatase PphA Is Required for Light-Dependent Control of Nitrate Utilization in Synechocystis sp. Strain PCC 6803

2005 ◽  
Vol 187 (19) ◽  
pp. 6683-6690 ◽  
Author(s):  
Nicole Kloft ◽  
Karl Forchhammer
Keyword(s):  
Signal Transduction ◽  
Protein Phosphatase ◽  
Nitrate Uptake ◽  
Photon Flux ◽  
Wild Type ◽  
Low Light ◽  
Signal Transduction Protein ◽  
The Impact ◽  
Reduction Capacity ◽  
Pcc 6803

ABSTRACT Signal transduction protein PII is dephosphorylated in Synechocystis sp. strain PCC 6803 by protein phosphatase PphA. To determine the impact of PphA-mediated PII dephosphorylation on physiology, the phenotype of a PphA-deficient mutant was analyzed. Mutants lacking either PphA or PII were impaired in efficient utilization of nitrate as the nitrogen source. Under conditions of limiting photosystem I (PSI)-reduced ferredoxin, excess reduction of nitrate along with impaired reduction of nitrite occurred in PII signaling mutants, resulting in excretion of nitrite to the medium. This effect could be reversed by increasing the level of PSI-reduced ferredoxin. We present evidence that nonphosphorylated PII controls the utilization of nitrate in response to low light intensity by tuning down nitrate uptake to meet the actual reduction capacity. This control mechanism can be bypassed by exposing cells to excess levels of nitrate. Uncontrolled nitrate uptake leads to light-dependent nitrite excretion even in wild-type cells, confirming that nitrate uptake controls nitrate utilization in response to limiting photon flux densities.

scholarly journals Morphological and Photosynthetic Response to High and Low Irradiance ofAeschynanthus longicaulis

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Qiansheng Li ◽  
Min Deng ◽  
Yanshi Xiong ◽  
Allen Coombes ◽  
Wei Zhao
Keyword(s):  
Light Stress ◽  
High Irradiance ◽  
Anthocyanin Content ◽  
Light Conditions ◽  
Leaf Color ◽  
Low Light ◽  
Light Levels ◽  
Chlorophyll Fluorescence Parameter ◽  
Fluorescence Parameter ◽  
Length Width

Aeschynanthus longicaulisplants are understory plants in the forest, adapting to low light conditions in their native habitats. To observe the effects of the high irradiance on growth and physiology, plants were grown under two different light levels, PPFD 650 μmol·m–2·s–1and 150 μmol·m–2·s–1for 6 months. Plants under high irradiance had significantly thicker leaves with smaller leaf area, length, width, and perimeter compared to the plants grown under low irradiance. Under high irradiance, the leaf color turned yellowish and the total chlorophyll decreased from 5.081 mg·dm−2to 3.367 mg·dm−2. The anthocyanin content of high irradiance leaves was double that of those under low irradiance. The plants under high irradiance had significantly lower Amax(5.69 μmol·m–2·s–1) and LSP (367 μmol·m–2·s–1) and higher LCP (21.9 μmol·m–2·s–1). The chlorophyll fluorescence parameterFv/Fmwas significantly lower and NPQ was significantly higher in high irradiance plants. RLCs showed significantly lowerETRmax⁡andEkin plants under high irradiance. It can be concluded that the maximum PPFD of 650 μmol·m–2·s–1led to significant light stress and photoinhibition ofA. longicaulis.

scholarly journals Photosystem II antenna modules CP43 and CP47 do not form a stable ‘no reaction centre complex’ in the cyanobacterium Synechocystis sp. PCC 6803

2022 ◽  
Author(s):  
Martina Bečková ◽  
Roman Sobotka ◽  
Josef Komenda
Keyword(s):  
Photosystem Ii ◽  
High Light ◽  
Oxygenic Photosynthesis ◽  
Reaction Centre ◽  
Wild Type ◽  
Migration Patterns ◽  
Separate Protein ◽  
Antenna Module ◽  
D2 Protein ◽  
Pcc 6803

AbstractThe repair of photosystem II is a key mechanism that keeps the light reactions of oxygenic photosynthesis functional. During this process, the PSII central subunit D1 is replaced with a newly synthesized copy while the neighbouring CP43 antenna with adjacent small subunits (CP43 module) is transiently detached. When the D2 protein is also damaged, it is degraded together with D1 leaving both the CP43 module and the second PSII antenna module CP47 unassembled. In the cyanobacterium Synechocystis sp. PCC 6803, the released CP43 and CP47 modules have been recently suggested to form a so-called no reaction centre complex (NRC). However, the data supporting the presence of NRC can also be interpreted as a co-migration of CP43 and CP47 modules during electrophoresis and ultracentrifugation without forming a mutual complex. To address the existence of NRC, we analysed Synechocystis PSII mutants accumulating one or both unassembled antenna modules as well as Synechocystis wild-type cells stressed with high light. The obtained results were not compatible with the existence of a stable NRC since each unassembled module was present as a separate protein complex with a mutually similar electrophoretic mobility regardless of the presence of the second module. The non-existence of NRC was further supported by isolation of the His-tagged CP43 and CP47 modules from strains lacking either D1 or D2 and their migration patterns on native gels.

scholarly journals Increased Production of Zeaxanthin and Other Pigments by Application of Genetic Engineering Techniques toSynechocystis sp. Strain PCC 6803

2000 ◽  
Vol 66 (1) ◽  
pp. 64-72 ◽  
Author(s):  
Delphine Lagarde ◽  
Laurent Beuf ◽  
Wim Vermaas
Keyword(s):  
Mutant Strain ◽  
Fold Increase ◽  
Carotenoid Biosynthesis ◽  
Carotenoid Content ◽  
Wild Type ◽  
Gene Encoding ◽  
Genes Encoding ◽  
In The Wild ◽  
Β Carotene ◽  
Pcc 6803

ABSTRACT The psbAII locus was used as an integration platform to overexpress genes involved in carotenoid biosynthesis inSynechocystis sp. strain PCC 6803 under the control of the strong psbAII promoter. The sequences of the genes encoding the yeast isopentenyl diphosphate isomerase (ipi) and theSynechocystis β-carotene hydroxylase (crtR) and the linked Synechocystis genes coding for phytoene desaturase and phytoene synthase (crtP andcrtB, respectively) were introduced intoSynechocystis, replacing the psbAII coding sequence. Expression of ipi, crtR, andcrtP and crtB led to a large increase in the corresponding transcript levels in the mutant strains, showing that the psbAII promoter can be used to drive transcription and to overexpress various genes in Synechocystis. Overexpression of crtP and crtB led to a 50% increase in the myxoxanthophyll and zeaxanthin contents in the mutant strain, whereas the β-carotene and echinenone contents remained unchanged. Overexpression of crtR induced a 2.5-fold increase in zeaxanthin accumulation in the corresponding overexpressing mutant compared to that in the wild-type strain. In this mutant strain, zeaxanthin becomes the major pigment (more than half the total amount of carotenoid) and the β-carotene and echinenone amounts are reduced by a factor of 2. However, overexpression of ipi did not result in a change in the carotenoid content of the mutant. To further alter the carotenoid content of Synechocystis, the crtOgene, encoding β-carotene ketolase, which converts β-carotene to echinenone, was disrupted in the wild type and in the overexpressing strains so that they no longer produced echinenone. In this way, by a combination of overexpression and deletion of particular genes, the carotenoid content of cyanobacteria can be altered significantly.

scholarly journals Role of NtcB in Activation of Nitrate Assimilation Genes in the Cyanobacterium Synechocystis sp. Strain PCC 6803

2001 ◽  
Vol 183 (20) ◽  
pp. 5840-5847 ◽  
Author(s):  
Makiko Aichi ◽  
Nobuyuki Takatani ◽  
Tatsuo Omata
Keyword(s):  
Nitrate Assimilation ◽  
Ammonium Assimilation ◽  
Dependent Manner ◽  
Wild Type ◽  
Transcriptional Enhancer ◽  
Genes Encoding ◽  
Different Strains ◽  
Pcc 7942 ◽  
Pcc 6803

ABSTRACT In Synechocystis sp. strain PCC 6803, the genes encoding the proteins involved in nitrate assimilation are organized into two transcription units,nrtABCD-narB and nirA, the expression of which was repressed by ammonium and induced by inhibition of ammonium assimilation, suggesting involvement of NtcA in the transcriptional regulation. Under inducing conditions, expression of the two transcription units was enhanced by nitrite, suggesting regulation by NtcB, the nitrite-responsive transcriptional enhancer we previously identified in Synechococcus sp. strain PCC 7942. The slr0395 gene, which encodes a protein 47% identical to Synechococcus NtcB, was identified as theSynechocystis ntcB gene, on the basis of the inability of an slr0395 mutant to rapidly accumulate the transcripts of the nitrate assimilation genes upon induction and to respond to nitrite. While Synechococcus NtcB strictly requires nitrite for its action, Synechocystis NtcB enhanced transcription significantly even in the absence of nitrite. Whereas the Synechococcus ntcB mutant expresses the nitrate assimilation genes to a significant level in an NtcA-dependent manner, the Synechocystis ntcB mutant showed only low-level expression of the nitrate assimilation genes, indicating that NtcA by itself cannot efficiently promote expression of these genes inSynechocystis. Activities of the nitrate assimilation enzymes in the Synechocystis ntcB mutant were consequently low, being 40 to 50% of the wild-type level, and the cells grew on nitrate at a rate approximately threefold lower than that of the wild-type strain. These results showed that the contribution of NtcB to the expression of nitrate assimilation capability varies considerably among different strains of cyanobacteria.

scholarly journals Inactivation of Ca2+/H+Exchanger in Synechocystis sp. Strain PCC 6803 Promotes Cyanobacterial Calcification by Upregulating CO2-Concentrating Mechanisms

2013 ◽  
Vol 79 (13) ◽  
pp. 4048-4055 ◽  
Author(s):  
Hai-Bo Jiang ◽  
Hui-Min Cheng ◽  
Kun-Shan Gao ◽  
Bao-Sheng Qiu
Keyword(s):  
Transcript Level ◽  
Wild Type ◽  
Content Type ◽  
Protein Levels ◽  
Genes Encoding ◽  
In The Wild ◽  
Co2 Concentrating Mechanisms ◽  
Mutant Cells ◽  
Global Carbon ◽  
Pcc 6803

ABSTRACTCyanobacteria are important players in the global carbon cycle, accounting for approximately 25% of global CO2fixation. Their CO2-concentrating mechanisms (CCMs) are thought to play a key role in cyanobacterial calcification, but the mechanisms are not completely understood. InSynechocystissp. strain PCC 6803, a single Ca2+/H+exchanger (Slr1336) controls the Ca2+/H+exchange reaction. We knocked out the exchanger and investigated the effects on cyanobacterial calcification and CCMs. Inactivation ofslr1336significantly increased the calcification rate and decreased the zeta potential, indicating a relatively stronger Ca2+-binding ability. Some genes encoding CCM-related components showed increased expression levels, including thecmpAgene, which encodes the Ca2+-dependent HCO3−transporter BCT1. The transcript level ofcmpAin the mutant was 30 times that in wild type. A Western blot analysis further confirmed that protein levels of CmpA were higher in the mutant than the wild type. Measurements of inorganic carbon fluxes and O2evolution proved that both the net HCO3−uptake rate and the BCT1 transporter supported photosynthetic rate in theslr1336mutant were significantly higher than in the wild type. This would cause the mutant cells to liberate more OH−ions out of the cell and stimulate CaCO3precipitation in the microenvironment. We conclude that the mutation of the Ca2+/H+exchanger inSynechocystispromoted the cyanobacterial calcification process by upregulating CCMs, especially the BCT1 HCO3−transporter. These results shed new light on the mechanism by which CCM-facilitated photosynthesis promotes cyanobacterial calcification.

scholarly journals The Entner-Doudoroff Pathway Contributes to Glycogen Breakdown During High to Low CO2 Shifts in the Cyanobacterium Synechocystis sp. PCC 6803

2021 ◽  
Vol 12 ◽  
Author(s):  
Stefan Lucius ◽  
Alexander Makowka ◽  
Klaudia Michl ◽  
Kirstin Gutekunst ◽  
Martin Hagemann
Keyword(s):  
Organic Compounds ◽  
Inorganic Carbon ◽  
Pentose Phosphate ◽  
Oxygenic Photosynthesis ◽  
Wild Type ◽  
Low Co2 ◽  
Glycogen Breakdown ◽  
Synechocystis Sp ◽  
Mutant Collection ◽  
Pcc 6803

Cyanobacteria perform plant-like oxygenic photosynthesis to convert inorganic carbon into organic compounds and can also use internal carbohydrate reserves under specific conditions. A mutant collection with defects in different routes for sugar catabolism was studied to analyze which of them is preferentially used to degrade glycogen reserves in light-exposed cells of Synechocystis sp. PCC 6803 shifted from high to low CO2 conditions. Mutants defective in the glycolytic Embden–Meyerhof–Parnas pathway or in the oxidative pentose-phosphate (OPP) pathway showed glycogen levels similar to wild type under high CO2 (HC) conditions and were able to degrade it similarly after shifts to low CO2 (LC) conditions. In contrast, the mutant Δeda, which is defective in the glycolytic Entner-Doudoroff (ED) pathway, accumulated elevated glycogen levels under HC that were more slowly consumed during the LC shift. In consequence, the mutant Δeda showed a lowered ability to respond to the inorganic carbon shifts, displayed a pronounced lack in the reactivation of growth when brought back to HC, and differed significantly in its metabolite composition. Particularly, Δeda accumulated enhanced levels of proline, which is a well-known metabolite to maintain redox balances via NADPH levels in many organisms under stress conditions. We suggest that deletion of eda might promote the utilization of the OPP shunt that dramatically enhance NADPH levels. Collectively, the results point at a major regulatory contribution of the ED pathway for the mobilization of glycogen reserves during rapid acclimation to fluctuating CO2 conditions.

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