The role of unsaturated fatty acids in membrane lipids in the tolerance of the photosynthetic machinery to salt stress was studied by comparing the desA-/desD- mutant of Synechocystis sp. PCC 6803, ...which contained monounsaturated fatty acids, with the wild-type strain, which contained a full complement of polyunsaturated fatty acids. In darkness, the loss of oxygen-evolving photosystem II activity in the presence of 0.5 M NaCl or 0.5 M LiCl was much more rapid in desA-/desD- cells than in wild-type cells. Oxygen-evolving activity that had been lost during incubation with 0.5 M NaCl in darkness returned when cells were transferred to conditions that allowed photosynthesis or respiration. Recovery was much greater in wild-type than in desA-/desD- cells, and it was prevented by lincomycin. Thus, the unsaturation of fatty acids is important in the tolerance of the photosynthetic machinery to salt stress. It appears also that the activity and synthesis of the Na+/H+ antiporter system might be suppressed under high-salt conditions and that this effect can be reversed, in part, by the unsaturation of fatty acids in membrane lipids.
Photosystem II in bio-photovoltaic devices VOLOSHIN, R.A.; SHUMILOVA, S.M.; ZADNEPROVSKAYA, E.V. ...
Photosynthetica,
3/2022, Letnik:
60, Številka:
SPECIAL ISSUE 2022
Journal Article
Recenzirano
Odprti dostop
Hybrid photoelectrodes containing biological pigment-protein complexes can be used for environmentally friendly solar energy conversion, herbicide detection, and other applications. The total number ...of scientific publications on hybrid bio-based devices has grown rapidly over the past decades. Particular attention is paid to the integration of the complexes of PSII into photoelectrochemical devices. A notable feature of these complexes from a practical point of view is their ability to obtain electrons from abundant water. The utilization or imitation of the PSII functionality seems promising for all of the following: generating photoelectricity, photo-producing hydrogen, and detecting herbicides. This review summarizes recent advances in the development of hybrid devices based on PSII. In a brief historical review, we also highlighted the use of quinone-type bacterial reaction centers in hybrid devices. These proteins are the first from which the photoelectricity signal was detected. The photocurrent in these first systems, developed in the 70s-80s, was about 1 nA cm-2. In the latest work, by Güzel et al. (2020), a stable current of about 888 μA cm-2 as achieved in a PSII-based solar cell. The present review is inspired by this impressive progress. The advantages, disadvantages, and future endeavors of PSII-inspired bio-photovoltaic devices are also presented.
The review considers the role of H2O2, 1O2, O 2 ·− , and the products of lipid peroxidation as signaling molecules in the processes of stress signal transduction in plants. The data concerning ...possible ROS participation in transduction of stress signals from chloroplasts to the nuclear genome, H2O2 involvement in transduction stress signals in cyanobacteria, and also the interactions between ROS and other signaling systems within the cell are presented. It is suggested that redox regulators, protein kinases/protein phosphatases, and transcription factors play a crucial role in the functioning of ROS-dependent signaling systems in the plant cell.
The effect of a typical polyaromatic hydrocarbon, naphthalene (Naph), on photosystem 2 (PS-2) photochemical activity in thylakoid membrane preparations and 20-day-old pea leaves was studied. Samples ...were incubated in water in the presence of Naph (0.078, 0.21, and 0.78 mM) for 0.5–24 h under white light illumination (15 μmol photons·m
−2
·s
−1
). The PS-2 activity was determined by studying fast and delayed chlorophyll (Chl)
a
fluorescence. Incubation of samples in water solutions at Naph concentrations of 0.21 and 0.78 mM led to a decrease in the maximum PS-2 quantum efficiency (F
v
/F
m
), noticeable changes in the polyphasic induction kinetics of fluorescence (OJIP), and a decrease in the amplitudes of the fast and slow components of delayed fluorescence of Chl
a
. The rate of release of electrolytes from leaves that were preliminarily incubated with Naph (0.21 mM) was also increased. Significant decrease in the fluorescence parameters in thylakoid membrane preparations was observed at Naph concentration of 0.03 mM and 12-min exposure of the samples. Chlorophyll (
a
and
b
) and carotenoid content (mg per gram wet mass) was insignificantly changed. The quantum yields of electron transfer from Q
A
to Q
B
(φ
ET2o
) and also to the PS-1 acceptors (φ
RE1o
) were reduced. These results are explained by the increase in the number of Q
B
-non-reducing centers of PS-2, which increased with increasing Naph concentration and exposure time of leaves in Naph solution. The suppression of PS-2 activity was partly abolished in the presence of the electron donor sodium ascorbate. Based on these results, it is suggested that Naph distorts cell membrane intactness and acts mainly on the PS-2 acceptor and to a lesser degree on the PS-2 donor side.
Heat stress is one of the major abiotic stresses and affects plant productivity in a negative manner. Photosynthetic processes are largely influenced by heat stress. In spinach (
Spinacia oleracea
...L.) leaves at 40°C the decrease in PSII activity was mainly due to the decreased efficiency to capture excitation energy, increased yield of regulatory energy dissipation mechanism Y(NPQ), and decreased quantum yield Y(II). According to the results below 45°C PSI is stable and protected while at a higher temperature stability of PSI was reduced and protection was not sufficient. Therefore, we conclude that cyclic electron flow plays an important role in protecting PSI from heat stress.
•The pea mutant Costata 2/133 exhibits decreased abundance of PSI complexes.•The pea mutant Costata 2/133 exhibits a limited capacity for state transitions.•Oligomerization of LHCII affects the ...susceptibility of PSI to high light stress.
Comparative analysis of in vivo chlorophyll fluorescence imaging revealed that photosystem II (PSII) photochemical efficiency (Fv/Fm) of leaves of the Costata 2/133 pea mutant with altered pigment composition and decreased level of oligomerization of the light harvesting chlorophyll a/b-protein complexes (LHCII) of PSII (Dobrikova et al., 2000; Ivanov et al., 2005) did not differ from that of WT. In contrast, photosystem I (PSI) activity of the Costata 2/133 mutant measured by the far-red (FR) light inducible P700 (P700+) signal exhibited 39% lower steady state level of P700+, a 2.2-fold higher intersystem electron pool size (e−/P700) and higher rate of P700+ re-reduction, which indicate an increased capacity for PSI cyclic electron transfer (CET) in the Costata 2/133 mutant than WT. The mutant also exhibited a limited capacity for state transitions. The lower level of oxidizable P700 (P700+) is consistent with a lower amount of PSI related chlorophyll protein complexes and lower abundance of the PsaA/PsaB heterodimer, PsaD and Lhca1 polypeptides in Costata 2/133 mutant. Exposure of WT and the Costata 2/133 mutant to high light stress resulted in a comparable photoinhibition of PSII measured in vivo, although the decrease of Fv/Fm was modestly higher in the mutant plants. However, under the same photoinhibitory conditions PSI photochemistry (P700+) measured as ΔA820−860 was inhibited to a greater extent (50%) in the Costata 2/133 mutant than in the WT (22%). This was accompanied by a 50% faster re-reduction rate of P700+ in the dark indicating a higher capacity for CET around PSI in high light treated mutant leaves. The role of chloroplast thylakoid organization on the stability of the PSI complex and its susceptibility to high light stress is discussed.
► We reported combined effects of red light (RL) and UV-A on photosynthetic apparatus (PA). ► Red light enhances resistance of photosynthetic apparatus to UV-A. ► Red light increases the content of ...UV-absorbing pigments and peroxidase activity. ► Preillumination with red light decreases the level of H2O2 induced with UV-A.
Seedlings of 10-day-old lettuce (Lactuca sativa L., cultivar Berlin) were preilluminated by low intensity red light (λmax=660nm, 10min, 5μmol quanta m−2s−1) and far-red light (λmax=730nm, 10min, 5μmol quanta m−2s−1) to study the effect of pre-treatment on photosynthesis, photochemical activity of photosystem II (PSII), the contents of photosynthetic and UV-A-absorbing pigments (UAPs) and H2O2, as well as total and ascorbate peroxidase activities in cotyledonary leaves of seedlings exposed to UV-A. UV radiation reduced the photosynthetic rate (Pn), the activity of PSII, and the contents of Chl a and b, carotenoids and UAPs in the leaves, but increased the content of H2O2 and the total peroxidase activity. Preillumination with red light removed these effects of UV. In turn, the illumination with red light, then far-red light removed the effect of the red light. Illumination with red light alone increased the content of UAPs, as well as peroxidase activity. It is suggested that higher resistance of the lettuce photosynthetic apparatus to UV-A radiation is associated with involvement of the active form of phytochrome B, thereby increasing peroxidase activities as well as UAPs and saving preservation of photosynthetic pigment contents due to pre-illumination with red light.
► Acetazolamide inhibits CA-activity and the PS II photosynthetic electron transfer. ► Acetazolamide-induced suppression is totally reversed by the addition of bicarbonate.► Similar effect was also ...revealed upon the addition of PS II electron donors.
The effects of suppression of the carbonic anhydrase (CA) activity by a CA-inhibitor, acetazolamide (AA), on the photosynthetic activities of photosystem II (PS II) particles from higher plants were investigated. AA along with CA-activity inhibits the PS II photosynthetic electron transfer and the AA-induced suppression is totally reversed by the addition of bicarbonate (3–5
mM). Similar effect of recovery in the PS II photosynthetic activity was also revealed upon the addition of known artificial electron donors (potassium ferrocyanide and TMPD). Significance and possible functions of CA for the PS II donor side are discussed.
Light stress and salt stress are major environmental factors that limit the efficiency of photosynthesis. However, we have found that the effects of light and salt stress on photosystem II (PSII) in ...the cyanobacterium Synechocystis sp. PCC 6803 are completely different. Strong light induced photodamage to PSII, whereas salt stress inhibited the repair of the photodamaged PSII and did not accelerate damage to PSII directly. The combination of light and salt stress appeared to inactivate PSII very rapidly as a consequence of their synergistic effects. Radioactive labeling of cells revealed that salt stress inhibited the synthesis of proteins de novo and, in particular, the synthesis of the D1 protein. Northern- and western-blotting analyses demonstrated that salt stress inhibited the transcription and the translation of psbA genes, which encode D1 protein. DNA microarray analysis indicated that the light-induced expression of various genes was suppressed by salt stress. Thus, our results suggest that salt stress inhibits the repair of PSII via suppression of the activities of the transcriptional and translational machinery.
Cyanobacteria, algae, and plants are the manufacturers that release O
2
via water oxidation during photosynthesis. Since fossil resources are running out, researchers are now actively trying to use ...the natural catalytic center of water oxidation found in the photosystem II (PS II) reaction center of oxygenic photosynthetic organisms to synthesize a biomimetic supercatalyst for water oxidation. Success in this area of research will transcend the current bottleneck for the development of energy-conversion schemes based on sunlight. In this review, we go over the structure and function of the water-oxidizing complex (WOC) found in Nature by focusing on the recent advances made by the international research community dedicated to achieve the goal of artificial water splitting based on the WOC of PS II.
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