OJIP chlorophyll fluorescence induction profiles and plastoquinone binding affinity of the Photosystem II assembly intermediate PSII-I from Thermosynechococcus elongatus

Photosystem Ii ◽

Binding Affinity ◽

Conformational Changes ◽

Charge Recombination ◽

Fluorescence Induction ◽

Acceptor Side ◽

Assembly Intermediate

Binding of Psb28 to the photosystem II assembly intermediate PSII-I induces conformational changes to the PSII acceptor side that impact charge recombination and reduce the in situ production of singlet oxygen (Zabret et al. 2021, Nat. Plants 7, 524-538). A detailed fluorometric analysis of the PSII-I assembly intermediate compared with OEC-disrupted and Mn-depleted PSII complexes showed differences between their variable (OJIP) chlorophyll fluorescence induction profiles. These revealed a distinct destabilisation of the QA- state in the PSII-I assembly intermediate and inactivated PSII samples related to an increased rate of direct and safe charge recombination. Furthermore, inactivation or removal of the OEC increases the binding affinity for plastoquinone analogues like DCBQ to the different PSII complexes. These results might indicate a mechanism that further contributes to the protection of PSII during biogenesis or repair.

How to build a water-splitting machine: structural insights into photosystem II assembly

10.21203/rs.3.rs-88039/v1 ◽

2020 ◽

Author(s):

Jure Zabret ◽

Stefan Bohn ◽

Sandra Schuller ◽

Oliver Arnolds ◽

Madeline Möller ◽

...

Keyword(s):

Photosystem Ii ◽

Water Splitting ◽

Conformational Changes ◽

Binding Pocket ◽

Heme Iron ◽

Structural Motif ◽

Acceptor Side ◽

Non Heme Iron ◽

Assembly Intermediate ◽

Stepwise Assembly

Abstract Biogenesis of photosystem II (PSII), nature’s water splitting catalyst, is assisted by auxiliary proteins that form transient complexes with PSII components to facilitate stepwise assembly events. Using cryo-electron microscopy, we solved the structure of such a PSII assembly intermediate with 2.94 Å resolution. It contains three assembly factors (Psb27, Psb28, Psb34) and provides detailed insights into their molecular function. Binding of Psb28 induces large conformational changes at the PSII acceptor side, which distort the binding pocket of the mobile quinone (QB) and replace bicarbonate with glutamate as a ligand of the non-heme iron, a structural motif found in reaction centers of non-oxygenic photosynthetic bacteria. These results reveal novel mechanisms that protect PSII from damage during biogenesis until water splitting is activated. Our structure further demonstrates how the PSII active site is prepared for the incorporation of the Mn4CaO5 cluster, which performs the unique water splitting reaction.

Humidity-sensitive Degreening and Regreening of Leaves of Borya nitida Labill. As Followed by Changes in Chlorophyll Fluorescence

Functional Plant Biology ◽

10.1071/pp9820587 ◽

1982 ◽

Vol 9 (5) ◽

pp. 587 ◽

Cited By ~ 12

Author(s):

SE Hethzerington ◽

RM Smillie

Keyword(s):

Relative Humidity ◽

Photosystem Ii ◽

Photosystem I ◽

Fluorescence Induction ◽

Physiological Age ◽

Induction Kinetics ◽

Mediated Electron Transfer

Fast and slow chlorophyll fluorescence induction kinetics were used to follow changes in photosynthetic activity during humidity-sensitive degreening and regreening of leaves of Borya nidita Labill. During dry periods the leaves of this desiccation-tolerant plant lose chlorophyll, becoming yellow-brown and upon rehydration turn green again. This degreening process can be simulated in detached leaves by slow dehydration at 96% relative humidity. Under these conditions changes in chlorophyll fluorescence in vivo and the activities of photosystems I and II in chloroplasts isolated from dehydrated leaves indicated that degreening was accompanied initially by a stimulation of photosystem II activity and a gradual decrease in photosystem I-mediated electron transfer, while at advanced stages of degreening both photosystems were lost. Control leaves detached and kept at 100% relative humidity remained green and showed little change in chlorophyll fluorescence kinetics. During the rehydration and subsequent regreening of dry yellow leaves, photosystem I activity appeared to recover faster than photosystem II. The ability of the leaves to recover and regreen from the dried state, either on the plant or after detachment, depended upon the physiological age of the leaves at the time of dehydration.

How to build a water-splitting machine: structural insights into photosystem II assembly

10.1101/2020.09.14.294884 ◽

2020 ◽

Author(s):

Jure Zabret ◽

Stefan Bohn ◽

Sandra K. Schuller ◽

Oliver Arnolds ◽

Madeline Möller ◽

...

Keyword(s):

Photosystem Ii ◽

Water Splitting ◽

Conformational Changes ◽

Binding Pocket ◽

Heme Iron ◽

Structural Motif ◽

Acceptor Side ◽

Assembly Factors ◽

Assembly Intermediate ◽

Stepwise Assembly

AbstractBiogenesis of photosystem II (PSII), nature’s water splitting catalyst, is assisted by auxiliary proteins that form transient complexes with PSII components to facilitate stepwise assembly events. Using cryo-electron microscopy, we solved the structure of such a PSII assembly intermediate with 2.94 Å resolution. It contains three assembly factors (Psb27, Psb28, Psb34) and provides detailed insights into their molecular function. Binding of Psb28 induces large conformational changes at the PSII acceptor side, which distort the binding pocket of the mobile quinone (QB) and replace bicarbonate with glutamate as a ligand of the non-heme iron, a structural motif found in reaction centers of non-oxygenic photosynthetic bacteria. These results reveal novel mechanisms that protect PSII from damage during biogenesis until water splitting is activated. Our structure further demonstrates how the PSII active site is prepared for the incorporation of the Mn4CaO5 cluster, which performs the unique water splitting reaction.One Sentence HighlightThe high-resolution Cryo-EM structure of the photosystem II assembly intermediate PSII-I reveals how nature’s water splitting catalyst is assembled, protected and prepared for photoactivation by help of the three assembly factors Psb27, Psb28 and Psb34.

The Inhibition of Photosynthetic Electron Transport by DBMIB and its Restoration by p-Phenylenediamines; Studied by Means of Prompt and Delayed Chlorophyll Fluorescence of Green Algae

Zeitschrift für Naturforschung C ◽

10.1515/znc-1974-11-1213 ◽

1974 ◽

Vol 29 (11-12) ◽

pp. 725-732 ◽

Cited By ~ 13

Author(s):

Robert Bauer ◽

Mathijs J. G. Wijnands

Keyword(s):

Electron Transport ◽

Photosystem Ii ◽

Photosynthetic Electron Transport ◽

Primary Electron ◽

Delayed Fluorescence ◽

Fluorescence Induction ◽

Exchange Reactions ◽

Redox Systems

Abstract The effect of the plastohydroquinone antagonist dibromothym oquinone (DBMIB) on photosynthetic electron transport reactions was studied in the presence and absence of p-phenylene-diamines by means of measurements of prompt and delayed chlorophyll fluorescence induction of the green alga Scenedesm us obliquus. Prompt and delayed chlorophyll fluorescence induction phenomena are valid indicators for the native presence of and cooperation between the two photosynthetic light reactions. Their kinetics reflect the balancing of electron exchange reactions in the chain of coupled redox-systems between the two photosystems upon sudden illumination. From distinct alterations of the short-term (sec) light induced changes in the yield of prom pt and delayed chlorophyll fluorescence it is concluded that DBMIB inhibits the photosynthetic electron transport in the chain of redox-systems between the two light reactions. There is evidence to show that upon illumination of DBMIB treated cells only the reduction of primary electron acceptor pools of photosystem II (i. e. Q and PQ) is still possible. After their reduction the further electron transport through photosystem II is blocked. The addition of p-phenylenediamines to DBM IB-treated cells abolishes the typical DBMIB-affected prom pt and delayed fluorescence inhibition curves and the normal induction curves re appear qualitatively in all their important features. From these measurements it is suggested that the redox properties of p-phenylenediamines allow an electron transport bypass of the DBMIB inhibition site which results in a fully restored photosynthetic electron transport from water to NADP.

Combined chlorophyll fluorescence techniques to study environmental impact on the mountain moss Polytrichum commune

Czech Polar Reports ◽

10.5817/cpr2021-1-12 ◽

2021 ◽

Vol 11 (1) ◽

pp. 161-173

Author(s):

Gabriella Nora Maria Giudici

Keyword(s):

Conformational Changes ◽

Heat Dissipation ◽

Fluorescence Induction ◽

High Light ◽

Photochemical Quenching ◽

Light Harvesting Complexes ◽

Polytrichum Commune ◽

Non Photochemical Quenching

Two chlorophyll fluorescence (ChlF) methods were used to study the effects of high light (photoinhibition) and dehydration, common stressors of the alpine environment, on primary photosynthetic processes in the moss Polytrichum commune from the Czech Republic, the Jeseníky Mountains. Photoinhibition (PI) was studied in fully hydrated thalli of P. commune and during the period of spontaneous desiccation. Time courses of Kautsky kinetics (KK) of ChlF and derived parameters: maximum quantum yield (FV/FM), effective quantum yeld (ΦPSII), and non-photochemical quenching parameters, were measured before and after the samples were treated with high light (1500 µmol m-2 s-1 PAR) for 60 min. Dehydration effects were tested in two sets of experiments with a Pulse-Amplitude-Modulation fluorometry (PAM) and Fast Chlorophyll Fluorescence induction curve (OJIP) techniques. In PAM tests, the desiccating samples were exposed to saturating light pulses every 10 min. in order to obtain ΦPSII and non-photochemical quenching (NPQ). In the second dehydration experiment, OJIP transients of ChlF were repeatedly recorded, OJIP-derived ChlF parameters were plotted against relative water content (RWC) monitored during desiccation. Combined ChF techniques provided insights into the mechanisms activated during P. commune desiccation, such as dissipation of excess absorbed energy through heat dissipation, and conformational changes or destructions of the light harvesting complexes. Combination of stressors resulted in amplified interference with the photosynthetic machinery, even when the added stressor (dehydration) was applied in low dose.

Chlorophyll fluorescence induction: an indicator of photosynthetic activity in marine algae undergoing desiccation

Canadian Journal of Botany ◽

10.1139/b78-334 ◽

1978 ◽

Vol 56 (21) ◽

pp. 2787-2794 ◽

Cited By ~ 59

Author(s):

James Wiltens ◽

Ulrich Schreiber ◽

William Vidaver

Keyword(s):

Electron Transport ◽

Photosystem Ii ◽

Water Content ◽

High Tide ◽

Net Photosynthesis ◽

Fluorescence Induction ◽

Physiological Basis ◽

Value Analysis

Algae of higher intertidal regions tend to be tolerant of extended periods of desiccation, while many lower tidal or subtidal species do not withstand even mild water loss. (Tidal regions can be characterized as high (regularly immersed at high tide and exposed at low tide), low (emergence only during minus tides (lower than mean low tide)), or subtidal (never exposed at low tide and extending to the maximum depth at which net photosynthesis can occur).) The ecological necessity for tolerance in frequently emerged species is obvious, but the physiological basis of it is not well understood. Changes of photosynthetic partial reactions upon desiccation and rehydration of tolerant and sensitive algae were studied by measurements of chlorophyll fluorescence induction kinetics (Kautsky effect). With progressive decrease in water content the gradual disappearance of the characteristic fluorescence transients was observed in both tolerant and sensitive species. The water content ranges where typical changes occurred were species dependent. Rehydration in tolerant plants resulted in rapid recovery from severe desiccation; there was no such recovery in sensitive plants when water content was decreased below a critical value. Analysis of the fluorescence changes upon desiccation and rehydration suggests: (1) electron transport between photosystem II and photosystem I, as well as H2O splitting are the partial reactions sensitive to desiccation; (2) in the resistant Porphyra sanjuanensis, intersystem electron transport is blocked at around 25% water content; (3) further desiccation leads to loss of water-splitting activity and eventually to the complete loss of variable fluorescence photosystem II reaction centers; and (4) on rehydration intersystem electron transport begins almost immediately while recovery of H2O splitting requires several minutes.

Kinetics of photosystem II electron transport: a mathematical analysis based on chlorophyll fluorescence induction

Photosynthesis Research ◽

10.1007/s11120-017-0439-y ◽

2017 ◽

Vol 136 (1) ◽

pp. 63-82 ◽

Cited By ~ 6

Author(s):

Agu Laisk ◽

Vello Oja

Keyword(s):

Electron Transport ◽

Photosystem Ii ◽

Mathematical Analysis ◽

Fluorescence Induction ◽

Kinetics Of

Respiration Interacts With Photosynthesis Through the Acceptor Side of Photosystem I, Reflected in the Dark-to-Light Induction Kinetics of Chlorophyll Fluorescence in the Cyanobacterium Synechocystis sp. PCC 6803

Frontiers in Plant Science ◽

10.3389/fpls.2021.717968 ◽

2021 ◽

Vol 12 ◽

Author(s):

Takako Ogawa ◽

Kenta Suzuki ◽

Kintake Sonoike

Keyword(s):

Electron Transport ◽

Photosystem I ◽

Fluorescence Induction ◽

Light Induction ◽

Acceptor Side ◽

Induction Kinetics ◽

Electron Transport Chains ◽

Kinetics Of

In cyanobacteria, the photosynthetic prokaryotes, direct interaction between photosynthesis and respiration exists at plastoquinone (PQ) pool, which is shared by the two electron transport chains. Another possible point of intersection of the two electron transport chains is NADPH, which is the major electron donor to the respiratory chain as well as the final product of the photosynthetic chain. Here, we showed that the redox state of NADPH in the dark affected chlorophyll fluorescence induction in the cyanobacterium Synechocystis sp. PCC 6803 in a quantitative manner. Accumulation of the reduced NADPH in the dark due to the defect in type 1 NAD(P)H dehydrogenase complex in the respiratory chain resulted in the faster rise to the peak in the dark-to-light induction of chlorophyll fluorescence, while depletion of NADPH due to the defect in pentose phosphate pathway resulted in the delayed appearance of the initial peak in the induction kinetics. There was a strong correlation between the dark level of NADPH determined by its fluorescence and the peak position of the induction kinetics of chlorophyll fluorescence. These results indicate that photosynthesis interacts with respiration through NADPH, which enable us to monitor the redox condition of the acceptor side of photosystem I by simple measurements of chlorophyll fluorescence induction in cyanobacteria.