Inhibition of Photosystem II by Ioxynil in Wild Type and Resistant Mutant of Synechocystis 6714

1989 ◽  
Vol 44 (11-12) ◽  
pp. 979-984 ◽  
Author(s):  
G. Ajlani ◽  
I. Meyer ◽  
C. Astier ◽  
C. Vernotte
Keyword(s):  
Electron Transfer ◽  
Photosystem Ii ◽  
Resistant Mutant ◽  
Psba Gene ◽  
Wild Type ◽  
Donor Side ◽  
Gene Encoding ◽  
Acceptor Side

Abstract A Synechocystis 6714 mutant resistant to the phenol-type herbicide ioxynil was isolated and characterized. Ioxynil was shown to inhibit both the donor and the acceptor sides of photosystem II, but at different concentrations. The mutation found in the psbA gene (encoding the D, protein) at codon 266 (asparagine to threonine) [G. Ajlani, I. Meyer, C. Vernotte, and C. Astier, FEBS Lett. 246, 207-210 (1989)] gives a ten-fold resistance of the acceptor side to ioxynil without any modification of the sensitivity of the donor side. Electron transfer between the primary and the secondary acceptor of photosystem II was identical in the mutant and the wild type. The mutant remains sensitive to atrazine and is even more sensitive to DCMU than the wild type.

scholarly journals The Acceptor Side of Photosystem II Is the Initial Target of Nitrite Stress in Synechocystis sp. Strain PCC 6803

2016 ◽  
Vol 83 (3) ◽  
Author(s):  
Xin Zhang ◽  
Fei Ma ◽  
Xi Zhu ◽  
Junying Zhu ◽  
Junfeng Rong ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Photosystem Ii ◽  
Donor Side ◽  
Electron Transfer Chain ◽  
Link Type ◽  
Acceptor Side ◽  
Psii Activity ◽  
Quinone Acceptor ◽  
Transfer Chain ◽  
Initial Target

ABSTRACT Nitrite, a common form of inorganic nitrogen (N), can be used as a nitrogen source through N assimilation. However, high levels of nitrite depress photosynthesis in various organisms. In this study, we investigated which components of the photosynthetic electron transfer chain are targeted by nitrite stress in Synechocystis sp. strain PCC 6803 cells. Measurements of whole-chain and photosystem II (PSII)-mediated electron transport activities revealed that high levels of nitrite primarily impair electron flow in PSII. Changes in PSII activity in response to nitrite stress occurred in two distinct phases. During the first phase, which occurred in the first 3 h of nitrite treatment, electron transfer from the primary quinone acceptor (QA) to the secondary quinone acceptor (QB) was retarded, as indicated by chlorophyll (Chl) a fluorescence induction, S-state distribution, and QA − reoxidation tests. In the second phase, which occurred after 6 h of nitrite exposure, the reaction center was inactivated and the donor side of photosystem II was inhibited, as revealed by changes in Chl fluorescence parameters and thermoluminescence and by immunoblot analysis. Our data suggest that nitrite stress is highly damaging to PSII and disrupts PSII activity by a stepwise mechanism in which the acceptor side is the initial target. IMPORTANCE In our previous studies, an alga-based technology was proposed to fix the large amounts of nitrite that are released from NOX-rich flue gases and proved to be a promising industrial strategy for flue gas NOX bioremediation (W. Chen et al., Environ Sci Technol 50:1620–1627, 2016, https://doi.org/10.1021/acs.est.5b04696 ; X. Zhang et al., Environ Sci Technol 48:10497–10504, 2014, https://doi.org/10.1021/es5013824 ). However, the toxic effects of high concentrations of nitrite on algal cells remain obscure. The analysis of growth rates, photochemistry, and protein profiles in our study provides important evidence that the inhibition by nitrite occurs in two phases: in the first phase, electron transfer between QA − and QB is retarded, whereas in the second, the donor side of PSII is affected. This is an excellent example of investigating the “early” inhibitory effects (i.e., within the first 6 h) on the PSII electron transfer chain in vivo. This paper provides novel insights into the mechanisms of nitrite inhibition of photosynthesis in an oxygenic phototrophic cyanobacterium.

Engineered ectopic expression of the psbA gene encoding the photosystem II D1 protein in Synechocystis sp. PCC6803

2007 ◽  
Vol 92 (3) ◽  
pp. 315-325 ◽  
Author(s):  
Madhavi Kommalapati ◽  
Hong Jin Hwang ◽  
Hong-Liang Wang ◽  
Robert L. Burnap
Keyword(s):  
Photosystem Ii ◽  
Ectopic Expression ◽  
D1 Protein ◽  
Psba Gene ◽  
Gene Encoding ◽  
Synechocystis Sp

scholarly journals Acceptor side effects on the electron transfer at cryogenic temperatures in intact photosystem II

2008 ◽  
Vol 1777 (9) ◽  
pp. 1109-1115 ◽  
Author(s):  
Han Bao ◽  
Chunxi Zhang ◽  
Keisuke Kawakami ◽  
Yanan Ren ◽  
Jian-Ren Shen ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Side Effects ◽  
Photosystem Ii ◽  
Cryogenic Temperatures ◽  
Acceptor Side

A New Ioxynil-Resistant Mutant in Synechocystis PCC 6714: Hypothesis on the Interaction of Ioxynil with the D1 Protein

1990 ◽  
Vol 45 (5) ◽  
pp. 436-440 ◽  
Author(s):  
S. Creuzet ◽  
G. Ajlani ◽  
C. Vernotte ◽  
C. Astier
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
D1 Protein ◽  
Resistant Mutant ◽  
Hydroxyl Group ◽  
Amino Acid Substitutions ◽  
Psba Gene ◽  
Molecular Models ◽  
Gene Encoding ◽  
Synechocystis Pcc 6714

A new Synechocystis 6714 mutant, loxIIA, resistant to the phenol-type herbicide ioxynil was isolated and characterized. The mutation found in the psbA gene (encoding the D1 photosystem II protein) is at the same codon 266 as for the first ioxynil-resistant mutant IoxIA previously selected [G. Ajlani. I. Meyer, C. Vernotte. and C. Astier, FEBS Lett. 246, 207-210 (1989)]. In IoxIIA, the change of Asn 266 to Asp gives a 3 × resistance, whereas in IoxIA, the change of the same amino acid to Thr gives a 10 × resistance. The effect of these different amino acid substitutions on the ioxynil resistance phenotype has allowed us to construct molecular models and calculate the hydrogen-bonding energies between the hydroxyl group of ioxynil and the respective amino acids at position 266.

scholarly journals An amino residue that guides the correct photoassembly the water-oxidation complex but not required for high affinity Mn2+ binding

2021 ◽  
Author(s):  
Anton P Avramov ◽  
Minquan Zhang ◽  
Robert L Burnap
Keyword(s):  
Photosystem Ii ◽  
Quantum Efficiency ◽  
Water Oxidation ◽  
Large Fraction ◽  
Wild Type ◽  
Donor Side ◽  
High Affinity ◽  
Initial Binding ◽  
Established Role

The assembly of the Mn4O5Ca cluster of the photosystem II (PSII) starts from the initial binding and photooxidation of the first Mn2+ at a high affinity site (HAS). Recent cryo-EM apo-PSII structures reveal an altered geometry of amino ligands in this region and suggest the involvement of D1-Glu189 ligand in the formation of the HAS. We now find that Gln and Lys substitution mutants photoactivate with reduced quantum efficiency compared to the wild-type. However, the affinity of Mn2+ at the HAS in D1-E189K was very similar to the wild-type (~2.2 μM). Thus, we conclude that D1-E189 does not form the HAS (~2.9 μM) and that the reduced quantum efficiency of photoactivation in D1-E189K cannot be ascribed to the initial photooxidation of Mn2+ at the HAS. Besides reduced quantum efficiency, the D1-E189K mutant exhibits a large fraction of centers that fail to recover activity during photoactivation starting early in the assembly phase, becoming recalcitrant to further assembly. Fluorescence relaxation kinetics indicate on the presence of an alternative route for the charge recombination in Mn-depleted samples in all studied mutants and exclude damage to the photochemical reaction center as the cause for the recalcitrant centers failing to assemble and show that dark incubation of cells reverses some of the inactivation. This reversibility would explain the ability of these mutants to accumulate a significant fraction of active PSII during extended periods of cell growth. The failed recovery in the fraction of inactive centers appears to a reversible mis-assembly involving the accumulation of photooxidized, but non-catalytic high valence Mn at the donor side of photosystem II, and that a reductive mechanism exists for restoration of assembly capacity at sites incurring mis-assembly. Given the established role of Ca2+ in preventing misassembled Mn, we conclude that D1-E189K mutant impairs the ligation of Ca2+ at its effector site in all PSII centers that consequently leads to the mis-assembly resulting in accumulation of non-catalytic Mn at the donor side of PSII. Our data indicate that D1-E189 is not functionally involved in Mn2+ oxidation\binding at the HAS but rather involved in Ca2+ ligation and steps following the initial Mn2+ photooxidation.

scholarly journals Properties of Photosystem II lacking the PsbJ subunit

2021 ◽  
Author(s):  
alain boussac ◽  
julien sellés ◽  
marion hamon ◽  
miwa sugiura
Keyword(s):  
Electron Transfer ◽  
Photosystem Ii ◽  
Energy Gap ◽  
Donor Side ◽  
Low Light ◽  
Time Resolved ◽  
Uv Visible ◽  
Assembly Intermediate ◽  
Α Helix ◽  
Oxygen Evolving

Photosystem II (PSII), the oxygen-evolving enzyme, consists of 17 trans-membrane and 3 extrinsic membrane proteins. Other subunits bind to PSII during assembly, like Psb27, Psb28, Tsl0063. The presence of Psb27 has been proposed (Zabret et al. 2021; Huang et al. 2021; Xiao et al. 2021) to prevent the binding of PsbJ, a single transmembrane α-helix close to the quinone QB binding site. Consequently, a PSII rid of Psb27, Psb28 and Tsl0034 prior to the binding of PsbJ would logically correspond to an assembly intermediate. The present work describes experiments aiming at further characterizing such a ΔPsbJ-PSII, purified from the thermophilic Thermosynechococcus elongatus, by means of MALDI-TOF spectroscopy, Thermoluminescence, EPR spectroscopy and UV-visible time-resolved spectroscopy. In the purified ΔPsbJ-PSII, an active Mn4CaO5 cluster is present in 60-70 % of the centers. In these centers, although the forward electron transfer seems not affected, the Em of the QB/QB- couple increases by ≈120 mV thus disfavoring the electron coming back on QA. The increase of the energy gap between QA/QA- and QB/QB- could contribute in a protection against the charge recombination between the donor side and QB-, identified at the origin of photoinhibition under low light (Keren et al. 1997), and possibly during the slow photoactivation process.

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