scholarly journals The algal PETC-Pro171-Leu suppresses electron transfer in the cytochrome b6f under acidic lumenal condition

2021 ◽  
Author(s):  
Shin-Ichiro Ozawa ◽  
Felix E. Buchert ◽  
Ruby Reuys ◽  
Michael Hippler ◽  
Yuichiro Takahashi
Keyword(s):  
Electron Flow ◽  
Vascular Plant ◽  
Potential Gradient ◽  
Light Conditions ◽  
Low Oxygen ◽  
Cytochrome B6f ◽  
Protection Mechanism ◽  
Sulfur Protein ◽  
Photosynthetic Control ◽  
Rieske Iron Sulfur Protein

Linear photosynthetic electron flow (LEF) produces NADPH and generates a proton electrochemical potential gradient across the thylakoid membrane used to synthesize ATP, both of which are required for CO2 fixation. As cellular demand for ATP and NADPH are variable, cyclic electron flow (CEF) between PSI and cytochrome b6f complex (b6f) produces extra ATP. The b6f regulates LEF and CEF via photosynthetic control, which is a pH-dependent b6f slowdown of plastoquinol oxidation at the lumenal site. This protection mechanism is triggered at more alkaline lumen pH in the pgr1 mutant of the vascular plant Arabidopsis thaliana, carrying Pro194Leu in the b6f Rieske Iron-sulfur protein. In this work, we introduced pgr1 mutation in the green alga Chlamydomonas reinhardtii (PETC-P171L). Consistent with pgr1 phenotype, PETC-P171L displayed a limited photosynthesis along with slower photoautotrophic growth under high light conditions. Our data under low oxygen revealed that the ΔpH component in algae was already sufficient to trigger the effect in PETC-P171L in sub-saturating light conditions where the mutant b6f was more restricted to oxidize the PQ pool and revealed a diminished electron flow.

Rieske iron-sulfur protein of cytochrome-b6f is involved in plant recovery after drought stress

2018 ◽  
Vol 156 ◽  
pp. 228-239 ◽  
Author(s):  
Tomasz Hura ◽  
Katarzyna Hura ◽  
Agnieszka Ostrowska ◽  
Joanna Gadzinowska ◽  
Maciej T. Grzesiak ◽  
...  
Keyword(s):  
Drought Stress ◽  
Cytochrome B6f ◽  
Plant Recovery ◽  
Iron Sulfur ◽  
Sulfur Protein ◽  
Iron Sulfur Protein ◽  
Rieske Iron Sulfur Protein

Non-Invasive Monitoring of the Light-Induced Cyclic Photosynthetic Electron Flow during Cold Hardening in Wheat Leaves

2006 ◽  
Vol 61 (9-10) ◽  
pp. 734-740 ◽  
Author(s):  
Simona Apostol ◽  
Gabriella Szalai ◽  
László Sujbert ◽  
Losanka P. Popova ◽  
Tibor Janda
Keyword(s):  
Winter Wheat ◽  
Electron Flow ◽  
Wheat Variety ◽  
Fluorescence Induction ◽  
Chlorophyll Fluorescence Induction ◽  
Light Conditions ◽  
Non Invasive ◽  
Photosynthetic Electron Flow ◽  
Temperature Hardening ◽  
Wheat Leaves

AbstractThe effect of irradiance during low temperature hardening was studied in a winter wheat variety. Ten-day-old winter wheat plants were cold-hardened at 5 °C for 11 days under light (250 μmol m-2 s-1) or dark (20 μmol m-2 s-1) conditions. The effectiveness of hardening was significantly lower in the dark, in spite of a slight decrease in the Fv/Fm chlorophyll fluorescence induction parameter, indicating the occurrence of photoinhibition during the hardening period in the light. Hardening in the light caused a downshift in the far-red induced AG (afterglow) thermoluminescence band. The faster dark re-reduction of P700+, monitored by 820-nm absorbance, could also be observed in these plants. These results suggest that the induction of cyclic photosynthetic electron flow may also contribute to the advantage of frost hardening under light conditions in wheat plants.

Spectroscopic methods in photosynthesis: photosystem stoichiometry and chlorophyll antenna size

1989 ◽  
Vol 323 (1216) ◽  
pp. 397-409 ◽  
Keyword(s):  
Plant Species ◽  
Light Harvesting ◽  
Electron Flow ◽  
Vascular Plant ◽  
Thylakoid Membranes ◽  
Reaction Centre ◽  
Antenna Size ◽  
Fluorescence Measurements ◽  
Photosystem Stoichiometry ◽  
Absorption Of Light

Light-induced absorbance change and fluorescence measurements were employed in the quantitation of photosystem stoichiometry and in the measurement of the chlorophyll (Chl) antenna size in thylakoid membranes. Results with thylakoid membranes from diverse photosynthetic tissues indicated a PSII/PSI reaction-centre stoichiometry that deviates from unity. Cyanobacteria and red algae have a PSII/PSI ratio in the range of 0.3 to 0.7. Chloroplasts from spinach and other vascular-plant species grown under direct sunlight have PSII/PSI = 1.8±0.3. Chlorophyll b -deficient and Chi b -lacking mutants have PSII/PSI > 2. The observation that PSII/PSI ratios are not unity and show a large variation among different photosynthetic membranes appears to be contrary to the conventional assumption derived from the Z-scheme. However, the photosystem stoichiometry is not the only factor that needs to be taken into account to explain the coordination of the two photosystems in the process of linear electron transport. The light-harvesting capacity of each photosystem must also be considered. In cyanobacterial thylakoids (from Synechococcus 6301, PSII/PSI = 0.5±0.2), the phycobilisome-PSII complexes collectively harvest as much light as the PSI complexes. In vascular plant chloroplasts, the light-harvesting capacity of a PSI I complex (250 molecules, Chi a/Chi b = 1.7) is lower than that of a PSI complex (230 Chl, Chl a /Chl b = 8.0) because Chi b has a lower extinction coefficient than Chi a . A differential attenuation of light intensity through the grana further reduces the light absorbed by PSII. Hence, a PSII/PSI ratio greater than one in vascular-plant chloroplasts compensates for the lower absorption of light by individual PSII complexes and ensures that, on average, PSII will harvest about as much light as PSI. In conclusion, distinct light-harvesting strategies among diverse plant species complement widely different photosystem stoichiometries to ensure a balanced absorption of light and a balanced electron flow between the two photoreactions, thereby satisfying the requirement set forth upon the formulation of the Z-scheme by Hill & Bendall ( Nature, Lond. 186, 136-137 (1960)) and by Duysens, Amesz & Kamp ( Nature, Lond . 190, 510-511 (1961)).

scholarly journals Ground vegetation diversity and geobotanical analysis in dune pine forests in southwest Estonia

2018 ◽  
Vol 69 (1) ◽  
pp. 63-74 ◽  
Author(s):  
Mari Tilk ◽  
Katri Ots ◽  
Tea Tullus ◽  
Malle Mandre
Keyword(s):  
Electrical Conductivity ◽  
Species Richness ◽  
Species Composition ◽  
Water Content ◽  
Soil Ph ◽  
Vascular Plant ◽  
Lichen Species ◽  
Ground Vegetation ◽  
Light Conditions ◽  
Vegetation Species

Abstract To investigate the ecosystems on dunes, five typical dunes were selected in the coastal area of the Baltic Sea in southwest Estonia. To study ground vegetation species richness, species composition and horizontal structure, 251 quadrats of 1 m2 in size were established and descriptions of vascular plants, bryophytes and lichen species were provided. Topographical factors, soil horizons, soil pH and electrical conductivity, soil nutrients, soil moisture conditions and light conditions were determined. In total, 42 vascular plant, 43 bryophyte and 48 lichen species were recorded on five dunes. Vascular plant species richness and composition on forested dunes was dependent on the absolute dune height, zone and aspect of the slope, soil nitrogen, potassium and phosphorus content, soil pH and moisture, the cover of the bryophyte-lichen layer and light conditions. Regarding bryophyte and lichen layer species composition, important factors were the aspect of the dune, vascular plant species cover, light conditions, the thickness of the moderately decomposed organic soil horizon, soil pH, electrical conductivity and volumetric water content. Lichen species richness was highest on the slopes of the dunes, while bryophyte species richness was higher at the bottoms and decreased towards the tops of the dunes. Ground vegetation species richness and species’ horizontal and vertical structure on forested dunes were highly dependent on topography-induced differences, aspect, height and zone of the dunes. The most important factors controlling the complex of ground vegetation were light conditions, soil water content, thickness of the moderately decomposed litter layer and soil potassium and calcium content.

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