Structural and functional role of the PsbH protein in resistance to light stress in Synechocystis PCC 6803

2002 ◽  
Vol 29 (10) ◽  
pp. 1181 ◽  
Author(s):  
Elisabetta Bergantino ◽  
Alessia Brunetta ◽  
Anna Segalla ◽  
Ildikò Szabò ◽  
Donatella Carbonera ◽  
...  
Keyword(s):  
Light Stress ◽  
D1 Protein ◽  
Complex Iii ◽  
Structural And Functional Properties ◽  
Primary Donor ◽  
Optically Detected ◽  
Oxygen Evolving ◽  
Psii Core Complex ◽  
Pcc 6803

Four mutants of the cyanobacterium Synechocystis sp. PCC 6803, carrying a modified PsbH subunit on a PSI-less background, were characterized by optically-detected magnetic resonance (ODMR), electron transport kinetics, and oxygen-evolving activity. Their relative tolerance to light stress was measured. Results indicate that: (i) the PsbH protein is deeply involved in determining structural and functional properties of the QB site on the D1 protein, whereas the environment of the primary donor P680 and its acceptors pheophytin and QA are not significantly affected by modifications of this subunit or its deletion; (ii) the charge recombination rate, in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), is reduced by a factor of 2, independently of the particular modification. The same result is found with the strain in which the subunit has been deleted. This result is taken as an indication that PsbH is important in regulating protein dynamics of the entire PSII core complex; (iii)�all investigated mutants display reduced tolerance to light stress, the extent of which depends on the particular modification. In this respect, mutations introduced in the transmembrane portion of the polypeptide are more effective than those involving the extramembrane N-terminal extension.

scholarly journals Role of Spermidine in Overwintering of Cyanobacteria

2015 ◽  
Vol 197 (14) ◽  
pp. 2325-2334 ◽  
Author(s):  
Xiangzhi Zhu ◽  
Qiong Li ◽  
Chuntao Yin ◽  
Xiantao Fang ◽  
Xudong Xu
Keyword(s):  
Gene Expression ◽  
Protein Synthesis ◽  
Light Stress ◽  
Protein Carbonylation ◽  
Cyanobacterial Blooms ◽  
Α Subunit ◽  
Content Type ◽  
Pcc 6803

ABSTRACTPolyamines are found in all groups of cyanobacteria, but their role in environmental adaptation has been barely investigated. InSynechocystissp. strain PCC 6803, inactivation of spermidine synthesis genes significantly reduced the survivability under chill (5°C)-light stress, and the survivability could be restored by addition of spermidine. To analyze the effects of spermidine on gene expression at 5°C,lacZwas expressed from the promoter of carboxy(nor)spermidine decarboxylase gene (CASDC) inSynechocystis.Synechocystis6803::PCASDC-lacZpretreated at 15°C showed a high level of LacZ activity for a long period of time at 5°C; without the pretreatment or with protein synthesis inhibited at 5°C, the enzyme activity gradually decreased. In a spermidine-minus mutant harboring PCASDC-lacZ,lacZshowed an expression pattern as if protein synthesis were inhibited at 5°C, even though the stability of its mRNA increased. Four other genes, includingrpoAthat encodes the α subunit of RNA polymerase, showed similar expression patterns. The chill-light stress led to a rapid increase of protein carbonylation inSynechocystis. The protein carbonylation then quickly returned to the background level in the wild type but continued to slowly increase in the spermidine-minus mutant. Our results indicate that spermidine promotes gene expression and replacement of damaged proteins in cyanobacteria under the chill-light stress in winter.IMPORTANCEOutbreak of cyanobacterial blooms in freshwater lakes is a worldwide environmental problem. In the annual cycle of bloom-forming cyanobacteria, overwintering is the least understood stage. Survival ofSynechocystissp. strain PCC 6803 under long-term chill (5°C)-light stress has been established as a model for molecular studies on overwintering of cyanobacteria. Here, we show that spermidine, the most common polyamine in cyanobacteria, promotes the survivability ofSynechocystisunder long-term chill-light stress and that the physiological function is based on its effects on gene expression and recovery from protein damage. This is the first report on the role of polyamines in survival of overwintering cyanobacteria. We also analyzed spermidine synthesis pathways in cyanobacteria on the basis of bioinformatic and experimental data.

scholarly journals α-Tocopherol Is Essential for Acquired Chill-Light Tolerance in the Cyanobacterium Synechocystis sp. Strain PCC 6803

2007 ◽  
Vol 190 (5) ◽  
pp. 1554-1560 ◽  
Author(s):  
Yang Yang ◽  
Chuntao Yin ◽  
Weizhi Li ◽  
Xudong Xu
Keyword(s):  
Escherichia Coli ◽  
Low Temperature ◽  
Light Stress ◽  
Wild Type ◽  
Regulated Expression ◽  
Synechocystis Sp ◽  
Pcc 6803

ABSTRACT Unlike Escherichia coli, the cyanobacterium Synechocystis sp. strain PCC 6803 is insensitive to chill (5°C) in the dark but rapidly losses viability when exposed to chill in the light (100 μmol photons m−2 s−1). Preconditioning at a low temperature (15°C) greatly enhances the chill-light tolerance of Synechocystis sp. strain PCC 6803. This phenomenon is called acquired chill-light tolerance (ACLT). Preconditioned wild-type cells maintained a substantially higher level of α-tocopherol after exposure to chill-light stress. Mutants unable to synthesize α-tocopherol, such as slr1736, slr1737, slr0089, and slr0090 mutants, almost completely lost ACLT. When exposed to chill without light, these mutants showed no or a slight difference from the wild type. When complemented, the slr0089 mutant regained its ACLT. Copper-regulated expression of slr0090 from P petE controlled the level of α-tocopherol and ACLT. We conclude that α-tocopherol is essential for ACLT of Synechocystis sp. strain PCC 6803. The role of α-tocopherol in ACLT may be based largely on a nonantioxidant activity that is not possessed by other tocopherols or pathway intermediates.

scholarly journals Singlet oxygen- and EXECUTER1-mediated signaling is initiated in grana margins and depends on the protease FtsH2

2016 ◽  
Vol 113 (26) ◽  
pp. E3792-E3800 ◽  
Author(s):  
Liangsheng Wang ◽  
Chanhong Kim ◽  
Xia Xu ◽  
Urszula Piskurewicz ◽  
Vivek Dogra ◽  
...  
Keyword(s):  
Singlet Oxygen ◽  
Light Stress ◽  
D1 Protein ◽  
Photosynthetic Electron Transport ◽  
Chlorophyll Synthesis ◽  
Light Conditions ◽  
Acceptor Side ◽  
Zinc Metalloprotease ◽  
Stress Acclimation

Formation of singlet oxygen (1O2) has been implicated with damaging photosystem II (PSII) that needs to undergo continuous repair to maintain photosynthetic electron transport. In addition to its damaging effect, 1O2 has also been shown to act as a signal that triggers stress acclimation and an enhanced stress resistance. A signaling role of 1O2 was first documented in the fluorescent (flu) mutant of Arabidopsis. It strictly depends on the chloroplast protein EXECUTER1 (EX1) and happens under nonphotoinhibitory light conditions. Under severe light stress, signaling is initiated independently of EX1 by 1O2 that is thought to be generated at the acceptor side of active PSII within the core of grana stacks. The results of the present study suggest a second source of 1O2 formation in grana margins close to the site of chlorophyll synthesis where EX1 is localized and the disassembly of damaged and reassembly of active PSII take place. The initiation of 1O2 signaling in grana margins depends on EX1 and the ATP-dependent zinc metalloprotease FtsH. As FtsH cleaves also the D1 protein during the disassembly of damaged PSII, EX1- and 1O2-mediated signaling seems to be not only spatially but also functionally associated with the repair of PSII.

scholarly journals Role of redox-inactive metals in controlling the redox potential of heterometallic manganese–oxido clusters

2021 ◽  
Author(s):  
Keisuke Saito ◽  
Minesato Nakagawa ◽  
Manoj Mandal ◽  
Hiroshi Ishikita
Keyword(s):  
Photosystem Ii ◽  
Redox Potential ◽  
Quantum Chemical Calculations ◽  
Catalytic Reaction ◽  
Quantum Chemical ◽  
Ionic Radius ◽  
Redox Potentials ◽  
Oxygen Evolving ◽  
Highest Occupied Molecular Orbitals

AbstractPhotosystem II (PSII) contains Ca2+, which is essential to the oxygen-evolving activity of the catalytic Mn4CaO5 complex. Replacement of Ca2+ with other redox-inactive metals results in a loss/decrease of oxygen-evolving activity. To investigate the role of Ca2+ in this catalytic reaction, we investigate artificial Mn3[M]O2 clusters redox-inactive metals  [M] ([M]  = Mg2+, Ca2+, Zn2+, Sr2+, and Y3+), which were synthesized by Tsui et al. (Nat Chem 5:293, 2013). The experimentally measured redox potentials (Em) of these clusters are best described by the energy of their highest occupied molecular orbitals. Quantum chemical calculations showed that the valence of metals predominantly affects Em(MnIII/IV), whereas the ionic radius of metals affects Em(MnIII/IV) only slightly.

scholarly journals A new insight into role of phosphoketolase pathway in Synechocystis sp. PCC 6803

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Anushree Bachhar ◽  
Jiri Jablonsky
Keyword(s):  
In Silico Analysis ◽  
Bioinformatic Analysis ◽  
Phosphoglycerate Mutase ◽  
Phosphoketolase Pathway ◽  
Multi Level ◽  
Silico Analysis ◽  
Insight Into ◽  
Synechocystis Sp ◽  
Pcc 6803

AbstractPhosphoketolase (PKET) pathway is predominant in cyanobacteria (around 98%) but current opinion is that it is virtually inactive under autotrophic ambient CO2 condition (AC-auto). This creates an evolutionary paradox due to the existence of PKET pathway in obligatory photoautotrophs. We aim to answer the paradox with the aid of bioinformatic analysis along with metabolic, transcriptomic, fluxomic and mutant data integrated into a multi-level kinetic model. We discussed the problems linked to neglected isozyme, pket2 (sll0529) and inconsistencies towards the explanation of residual flux via PKET pathway in the case of silenced pket1 (slr0453) in Synechocystis sp. PCC 6803. Our in silico analysis showed: (1) 17% flux reduction via RuBisCO for Δpket1 under AC-auto, (2) 11.2–14.3% growth decrease for Δpket2 in turbulent AC-auto, and (3) flux via PKET pathway reaching up to 252% of the flux via phosphoglycerate mutase under AC-auto. All results imply that PKET pathway plays a crucial role under AC-auto by mitigating the decarboxylation occurring in OPP pathway and conversion of pyruvate to acetyl CoA linked to EMP glycolysis under the carbon scarce environment. Finally, our model predicted that PKETs have low affinity to S7P as a substrate.

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