scholarly journals Sll1717 Affects the Redox State of the Plastoquinone Pool by Modulating Quinol Oxidase Activity in Thylakoids

2006 ◽  
Vol 188 (4) ◽  
pp. 1286-1294 ◽  
Author(s):  
Galyna I. Kufryk ◽  
Wim F. J. Vermaas
Keyword(s):  
Transcript Level ◽  
Wild Type ◽  
Low Light ◽  
Quinol Oxidase ◽  
Plastoquinone Pool ◽  
Light Intensities ◽  
In The Wild ◽  
Plausible Mechanism ◽  
Selection For ◽  
Pcc 6803

ABSTRACT A Synechocystis sp. strain PCC 6803 mutant lacking CtaI, a main subunit of cytochrome c oxidase, is not capable of growing at light intensities below 5 μmol photons m−2 s−1, presumably due to an overreduced plastoquinone pool in the thylakoid membrane. Upon selection for growth at light intensities below 5 μmol photons m−2 s−1, a secondary mutant was generated that retained the CtaI deletion and had fully assembled photosystem II complexes; in this secondary mutant (pseudorevertant), oxygen evolution and respiratory activities were similar to those in the wild type. Functional complementation of the original CtaI-less strain to low-light tolerance by transformation with restriction fragments of genomic DNA of the pseudorevertant and subsequent mapping of the pseudoreversion site showed that the point mutation led to a Ser186Cys substitution in Sll1717, a protein of as-yet-unknown function and with a predicted ATP/GTP-binding domain. This mutation caused a decrease in the plastoquinone pool reduction level of thylakoids compared to that observed for the wild type. Based on a variety of experimental evidence, the most plausible mechanism to cause this effect is an activation of plastoquinol oxidation in thylakoids by the quinol oxidase CydAB that occurs without upregulation of the corresponding gene and that may be caused by an increased CydAB activity in thylakoids, conceivably due to altered CydAB sorting between cytoplasmic and thylakoid membranes. Sll1717 appears to be unique to Synechocystis sp. strain PCC 6803 and has a close homologue encoded in the genome of this organism. The transcript level of sll1717 is low, which suggests that the corresponding protein is regulatory rather than structural.

scholarly journals Involvement of the SppA1 Peptidase in Acclimation to Saturating Light Intensities in Synechocystis sp. Strain PCC 6803

2004 ◽  
Vol 186 (12) ◽  
pp. 3991-3999 ◽  
Author(s):  
E. Pojidaeva ◽  
V. Zinchenko ◽  
S. V. Shestakov ◽  
A. Sokolenko
Keyword(s):  
Light Intensity ◽  
Wild Type Strain ◽  
Wild Type ◽  
Additional Mechanism ◽  
Gene Encoding ◽  
Light Intensities ◽  
In The Wild ◽  
Pcc 6803

ABSTRACT The sll1703 gene, encoding an Arabidopsis homologue of the thylakoid membrane-associated SppA peptidase, was inactivated by interposon mutagenesis in Synechocystis sp. strain PCC 6803. Upon acclimation from a light intensity of 50 to 150 μE m−2 s−1, the mutant preserved most of its phycobilisome content, whereas the wild-type strain developed a bleaching phenotype due to the loss of about 40% of its phycobiliproteins. Using in vivo and in vitro experiments, we demonstrate that the ΔsppA1 strain does not undergo the cleavage of the LR 33 and LCM 99 linker proteins that develops in the wild type exposed to increasing light intensities. We conclude that a major contribution to light acclimation under a moderate light regime in cyanobacteria originates from an SppA1-mediated cleavage of phycobilisome linker proteins. Together with changes in gene expression of the major phycobiliproteins, it contributes an additional mechanism aimed at reducing the content in phycobilisome antennae upon acclimation to a higher light intensity.

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 Identification and molecular characterization of a Chlamydomonas reinhardtii mutant that shows a light intensity dependent progressive chlorophyll deficiency

F1000Research ◽  
2013 ◽  
Vol 2 ◽  
pp. 142
Author(s):  
Phillip B Grovenstein ◽  
Darryel A Wilson ◽  
Kathryn D Lankford ◽  
Kelsey A Gaston ◽  
Surangi Perera ◽  
...  
Keyword(s):  
Light Intensity ◽  
Insertional Mutagenesis ◽  
Protoporphyrin Ix ◽  
Model Organism ◽  
Genomic Region ◽  
Oxygenic Photosynthesis ◽  
Autotrophic Growth ◽  
Wild Type ◽  
Light Intensities ◽  
In The Wild

The green micro-alga Chlamydomonas reinhardtii is an elegant model organism to study all aspects of oxygenic photosynthesis. Chlorophyll (Chl) and heme are major tetrapyrroles that play an essential role in energy metabolism in photosynthetic organisms. These tetrapyrroles are synthesized via a common branched pathway that involves mainly nuclear encoded enzymes. One of the enzymes in the pathway is Mg chelatase (MgChel) which inserts Mg2+ into protoporphyrin IX (PPIX, proto) to form Magnesium-protoporphyrin IX (MgPPIX, Mgproto), the first biosynthetic intermediate in the Chl branch. The GUN4 (genomes uncoupled 4) protein is not essential for the MgChel activity but has been shown to significantly stimulate its activity. We have isolated a light sensitive mutant, 6F14, by random DNA insertional mutagenesis. 6F14 cannot tolerate light intensities higher than 90-100 μmol photons m-2 s-1. It shows a light intensity dependent progressive photo-bleaching. 6F14 is incapable of photo-autotrophic growth under light intensity higher than 100 μmol photons m-2 s-1. PCR based analyses show that in 6F14 the insertion of the plasmid outside the GUN4 locus has resulted in a genetic rearrangement of the GUN4 gene and possible deletions in the genomic region flanking the GUN4 gene. Our gun4 mutant has a Chl content very similar to that in the wild type in the dark and is very sensitive to fluctuations in the light intensity in the environment unlike the earlier identified Chlamydomonas gun4 mutant. Complementation with a functional copy of the GUN4 gene restored light tolerance, Chl biosynthesis and photo-autotrophic growth under high light intensities in 6F14. 6F14 is the second gun4 mutant to be identified in C. reinhardtii. Additionally, we show that our two gun4 complements over-express the GUN4 protein and show a higher Chl content per cell compared to that in the wild type strain.

scholarly journals Role of Sigma Factors in Controlling Global Gene Expression in Light/Dark Transitions in the Cyanobacterium Synechocystis sp. Strain PCC 6803

2007 ◽  
Vol 189 (21) ◽  
pp. 7829-7840 ◽  
Author(s):  
Tina C. Summerfield ◽  
Louis A. Sherman
Keyword(s):  
Gene Expression ◽  
Global Gene Expression ◽  
Growth Conditions ◽  
Day Length ◽  
Regulation Of Transcription ◽  
Wild Type ◽  
Protein Levels ◽  
In The Wild ◽  
Altered Gene ◽  
Pcc 6803

ABSTRACT We report on differential gene expression in the cyanobacterium Synechocystis sp. strain PCC 6803 after light-dark transitions in wild-type, ΔsigB, and ΔsigD strains. We also studied the effect of day length in the presence of glucose on a ΔsigB ΔsigE mutant. Our results indicated that the absence of SigB or SigD predominately altered gene expression in the dark or in the light, respectively. In the light, approximately 350 genes displayed transcript levels in the ΔsigD strain that were different from those of the wild type, with over 200 of these up-regulated in the mutant. In the dark, removal of SigB altered more than 150 genes, and the levels of 136 of these were increased in the mutant compared to those in the wild type. The removal of both SigB and SigE had a major impact on gene expression under mixotrophic growth conditions and resulted in the inability of cells to grow in the presence of glucose with 8-h light and 16-h dark cycles. Our results indicated the importance of group II σ factors in the global regulation of transcription in this organism and are best explained by using the σ cycle paradigm with the stochastic release model described previously (R. A. Mooney, S. A. Darst, and R. Landick, Mol. Cell 20:335-345, 2005). We combined our results with the total protein levels of the σ factors in the light and dark as calculated previously (S. Imamura, S. Yoshihara, S. Nakano, N. Shiozaki, A. Yamada, K. Tanaka, H. Takahashi, M. Asayama, and M. Shirai, J. Mol. Biol. 325:857-872, 2003; S. Imamura, M. Asayama, H. Takahashi, K. Tanaka, H. Takahashi, and M. Shirai, FEBS Lett. 554:357-362, 2003). Thus, we concluded that the control of global transcription is based on the amount of the various σ factors present and able to bind RNA polymerase.

Photosystem II activity of wild type Synechocystis PCC 6803 and its mutants with different plastoquinone pool redox states

2016 ◽  
Vol 81 (8) ◽  
pp. 858-870
Author(s):  
O. V. Voloshina ◽  
Y. V. Bolychevtseva ◽  
F. I. Kuzminov ◽  
M. Y. Gorbunov ◽  
I. V. Elanskaya ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Wild Type ◽  
Synechocystis Pcc 6803 ◽  
Redox States ◽  
Plastoquinone Pool ◽  
Photosystem Ii Activity ◽  
Pcc 6803

scholarly journals Complexome profiling on the lpa2 mutant reveals insights into PSII biogenesis and new PSII associated proteins

2021 ◽  
Author(s):  
Benjamin Spaniol ◽  
Julia Lang ◽  
Benedikt Venn ◽  
Lara Schake ◽  
Frederik K Sommer ◽  
...  
Keyword(s):  
Complex Dynamics ◽  
Oxygen Evolving Complex ◽  
Cytochrome B6f Complex ◽  
Wild Type ◽  
Low Light ◽  
Chlorophyll Breakdown ◽  
Associated Proteins ◽  
In The Wild ◽  
Oxygen Evolving ◽  
B6f Complex

We have identified the homolog of LOW PSII ACCUMULATION 2 (LPA2) in Chlamydomonas. A Chlamydomonas lpa2 mutant grew slower in low light and was hypersensitive to high light. PSII maximum quantum efficiency was reduced by 38%. Synthesis and stability of newly made PSII core subunits D1, D2, CP43, and CP47 were not impaired. Complexome profiling revealed that in the mutant CP43 was reduced to ~23%, D1, D2, and CP47 to ~30% of wild-type levels, while small PSII core subunits and components of the oxygen evolving complex were reduced at most by factor two. PSII supercomplexes, dimers, and monomers were reduced to 7%, 26%, and 60% of wild-type levels, while RC47 was increased ~6-fold. Our data indicate that LPA2 acts at a step during PSII assembly without which PSII monomers and especially further assemblies become intrinsically unstable and prone to degradation. Levels of ATP synthase and LHCII were 29% and 27% higher in the mutant than in the wild type, whereas levels of the cytochrome b6f complex were unaltered. While the abundance of PSI core subunits and antennae hardly changed, LHCI antennae were more disconnected in the lpa2 mutant, presumably as an adaptive response to reduce excitation of PSI. The disconnection of LHCA2,9 together with PSAH and PSAG was the prime response, but independent and additional disconnection of LHCA1,3-8 along with PSAK occurred as well. Finally, based on co-migration profiles, we identified three novel putative PSII associated proteins with potential roles in regulating PSII complex dynamics, assembly, and chlorophyll breakdown.

The Kok Effect and Its Relationship to Photorespiration in Tobacco

1981 ◽  
Vol 36 (5-6) ◽  
pp. 450-454
Author(s):  
Ryuichi Ishii ◽  
Georg H. Schmid
Keyword(s):  
Mass Spectrometry ◽  
Structural Change ◽  
Light Intensity ◽  
Dark Respiration ◽  
Hill Reaction ◽  
Wild Type ◽  
Intensity Curve ◽  
Low Light ◽  
In The Wild ◽  
The Hill

Abstract The Kok effect of photosynthesis was investigated in different tobacco mutants. It was found that the breaks in the light intensity curve were always at or around 1000 lux in all plants tested regardless of the unit sizes which differed by a factor of 10. It was concluded that the photo­ receptor responsible for the effect must be present in the wild type and the chlorophyll deficient mutants in the same amount and is probably not chlorophyll. Due to the fact that the light dependency of the Hill reaction in isolated tobacco chloroplasts also shows a break at or around the “Kok intensity” it was concluded that probably a structural change of the photochemical apparatus around 1000 lux contributes to the effect. Measurement of 180 2-uptake by mass spectrometry at low light intensity shows at low CO2-concentration an enhancement of 180 2-uptake again at/around 1000 lux indicating that photorespiration starts to function at the “Kok intensity”. Due to the fact that 180 2-uptake remains constant at high CO2-concentrations the break in the photosynthetic light intensity curve cannot be due to an inhibition of “dark respiration” at low light intensities.

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 Coiled-coil registry shifts in the F684I mutant of Bicaudal result in cargo-independent activation of dynein motility

2019 ◽  
Author(s):  
Heying Cui ◽  
Kathleen M. Trybus ◽  
M. Yusuf Ali ◽  
Puja Goyal ◽  
Kaiqi Zhang ◽  
...  
Keyword(s):  
Coiled Coil ◽  
Underlying Mechanism ◽  
Structural Flexibility ◽  
Human Homolog ◽  
Wild Type ◽  
Transport Pathways ◽  
X Ray ◽  
In The Wild ◽  
Selection For ◽  
Dependent Transport

ABSTRACTThe dynein adaptor Drosophila Bicaudal D (BicD) is auto-inhibited and activates dynein motility only after cargo is bound, but the underlying mechanism is elusive. In contrast, we show that the full-length BicD/F684I mutant activates dynein processivity even in the absence of cargo. Our X-ray structure of the C-terminal domain of the BicD/F684I mutant reveals a coiled-coil registry shift; in the N-terminal region, the two helices of the homodimer are aligned, whereas they are vertically shifted in the wild-type. One chain is partially disordered and this structural flexibility is confirmed by computations, which reveal that the mutant transitions back and forth between the two registries. We propose that a coiled-coil registry shift upon cargo binding activates BicD for dynein recruitment. Moreover, the human homolog BicD2/F743I exhibits diminished binding of cargo adaptor Nup358, implying that a coiled-coil registry shift may be a mechanism to modulate cargo selection for BicD2–dependent transport pathways.

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