scholarly journals Hacking the thylakoid proton motive force for improved photosynthesis: modulating ion flux rates that control proton motive force partitioning into Δ ψ and ΔpH

2017 ◽  
Vol 372 (1730) ◽  
pp. 20160381 ◽  
Author(s):  
Geoffry A. Davis ◽  
A. William Rutherford ◽  
David M. Kramer
Keyword(s):  
Thylakoid Membrane ◽  
Proton Motive Force ◽  
Motive Force ◽  
Ion Fluxes ◽  
Dynamic Responses ◽  
Photochemical Quenching ◽  
Rapid Decline ◽  
Slow Kinetics ◽  
Dependent Form

There is considerable interest in improving plant productivity by altering the dynamic responses of photosynthesis in tune with natural conditions. This is exemplified by the ‘energy-dependent' form of non-photochemical quenching ( q E ), the formation and decay of which can be considerably slower than natural light fluctuations, limiting photochemical yield. In addition, we recently reported that rapidly fluctuating light can produce field recombination-induced photodamage (FRIP), where large spikes in electric field across the thylakoid membrane (Δ ψ ) induce photosystem II recombination reactions that produce damaging singlet oxygen ( 1 O 2 ). Both q E and FRIP are directly linked to the thylakoid proton motive force ( pmf ), and in particular, the slow kinetics of partitioning pmf into its ΔpH and Δ ψ components. Using a series of computational simulations, we explored the possibility of ‘hacking' pmf partitioning as a target for improving photosynthesis. Under a range of illumination conditions, increasing the rate of counter-ion fluxes across the thylakoid membrane should lead to more rapid dissipation of Δ ψ and formation of ΔpH. This would result in increased rates for the formation and decay of q E while resulting in a more rapid decline in the amplitudes of Δ ψ -spikes and decreasing 1 O 2 production. These results suggest that ion fluxes may be a viable target for plant breeding or engineering. However, these changes also induce transient, but substantial mismatches in the ATP : NADPH output ratio as well as in the osmotic balance between the lumen and stroma, either of which may explain why evolution has not already accelerated thylakoid ion fluxes. Overall, though the model is simplified, it recapitulates many of the responses seen in vivo , while spotlighting critical aspects of the complex interactions between pmf components and photosynthetic processes. By making the programme available, we hope to enable the community of photosynthesis researchers to further explore and test specific hypotheses. This article is part of the themed issue ‘Enhancing photosynthesis in crop plants: targets for improvement’.

In vivo regulation of proton motive force during photosynthetic induction

2018 ◽  
Vol 148 ◽  
pp. 109-116 ◽  
Author(s):  
Wei Huang ◽  
Xue Quan ◽  
Shi-Bao Zhang ◽  
Tao Liu
Keyword(s):  
Proton Motive Force ◽  
Motive Force ◽  
Photosynthetic Induction

scholarly journals In Vivo Synthesis of the Periplasmic Domain of TonB Inhibits Transport through the FecA and FhuA Iron Siderophore Transporters of Escherichia coli

2001 ◽  
Vol 183 (20) ◽  
pp. 5885-5895 ◽  
Author(s):  
S. Peter Howard ◽  
Christina Herrmann ◽  
Chad W. Stratilo ◽  
V. Braun
Keyword(s):  
Escherichia Coli ◽  
Cytoplasmic Membrane ◽  
Signal Sequence ◽  
Outer Membrane Proteins ◽  
Proton Motive Force ◽  
Motive Force ◽  
In Vivo Studies ◽  
Siderophore Transport

ABSTRACT The siderophore transport activities of the two outer membrane proteins FhuA and FecA of Escherichia coli require the proton motive force of the cytoplasmic membrane. The energy of the proton motive force is postulated to be transduced to the transport proteins by a protein complex that consists of the TonB, ExbB, and ExbD proteins. In the present study, TonB fragments lacking the cytoplasmic membrane anchor were exported to the periplasm by fusing them to the cleavable signal sequence of FecA. Overexpressed TonB(33-239), TonB(103-239), and TonB(122-239) fragments inhibited transport of ferrichrome by FhuA and of ferric citrate by FecA, transcriptional induction of the fecABCDE transport genes by FecA, infection by phage φ80, and killing of cells by colicin M via FhuA. Transport of ferrichrome by FhuAΔ5-160 was also inhibited by TonB(33-239), although FhuAΔ5-160 lacks the TonB box which is involved in TonB binding. The results show that TonB fragments as small as the last 118 amino acids of the protein interfere with the function of wild-type TonB, presumably by competing for binding sites at the transporters or by forming mixed dimers with TonB that are nonfunctional. In addition, the interactions that are inhibited by the TonB fragments must include more than the TonB box, since transport through corkless FhuA was also inhibited. Since the periplasmic TonB fragments cannot assume an energized conformation, these in vivo studies also agree with previous cross-linking and in vitro results, suggesting that neither recognition nor binding to loaded siderophore receptors is the energy-requiring step in the TonB-receptor interactions.

A Thylakoid-Located Two-Pore K+ Channel Controls Photosynthetic Light Utilization in Plants

Science ◽  
2013 ◽  
Vol 342 (6154) ◽  
pp. 114-118 ◽  
Author(s):  
Luca Carraretto ◽  
Elide Formentin ◽  
Enrico Teardo ◽  
Vanessa Checchetto ◽  
Martino Tomizioli ◽  
...  
Keyword(s):  
Thylakoid Membrane ◽  
Proton Motive Force ◽  
Motive Force ◽  
K Channel ◽  
Channel Activity ◽  
Membrane Organization ◽  
Physiological Functions ◽  
Environmental Stimuli ◽  
Light Utilization ◽  
Selective Channel

The size of the light-induced proton motive force (pmf) across the thylakoid membrane of chloroplasts is regulated in response to environmental stimuli. Here, we describe a component of the thylakoid membrane, the two-pore potassium (K+) channel TPK3, which modulates the composition of the pmf through ion counterbalancing. Recombinant TPK3 exhibited potassium-selective channel activity sensitive to Ca2+ and H+. In Arabidopsis plants, the channel is found in the thylakoid stromal lamellae. Arabidopsis plants silenced for the TPK3 gene display reduced growth and altered thylakoid membrane organization. This phenotype reflects an impaired capacity to generate a normal pmf, which results in reduced CO2 assimilation and deficient nonphotochemical dissipation of excess absorbed light. Thus, the TPK3 channel manages the pmf necessary to convert photochemical energy into physiological functions.

scholarly journals From isolated light-harvesting complexes to the thylakoid membrane: a single-molecule perspective

Nanophotonics ◽  
2018 ◽  
Vol 7 (1) ◽  
pp. 81-92 ◽  
Author(s):  
J. Michael Gruber ◽  
Pavel Malý ◽  
Tjaart P.J. Krüger ◽  
Rienk van Grondelle
Keyword(s):  
Single Molecule ◽  
Thylakoid Membrane ◽  
Light Harvesting ◽  
Protein Complexes ◽  
Conformational Dynamics ◽  
Physical Models ◽  
Photochemical Quenching ◽  
Light Harvesting Complexes ◽  
Fluorescence Measurements

AbstractThe conversion of solar radiation to chemical energy in plants and green algae takes place in the thylakoid membrane. This amphiphilic environment hosts a complex arrangement of light-harvesting pigment-protein complexes that absorb light and transfer the excitation energy to photochemically active reaction centers. This efficient light-harvesting capacity is moreover tightly regulated by a photoprotective mechanism called non-photochemical quenching to avoid the stress-induced destruction of the catalytic reaction center. In this review we provide an overview of single-molecule fluorescence measurements on plant light-harvesting complexes (LHCs) of varying sizes with the aim of bridging the gap between the smallest isolated complexes, which have been well-characterized, and the native photosystem. The smallest complexes contain only a small number (10–20) of interacting chlorophylls, while the native photosystem contains dozens of protein subunits and many hundreds of connected pigments. We discuss the functional significance of conformational dynamics, the lipid environment, and the structural arrangement of this fascinating nano-machinery. The described experimental results can be utilized to build mathematical-physical models in a bottom-up approach, which can then be tested on larger in vivo systems. The results also clearly showcase the general property of biological systems to utilize the same system properties for different purposes. In this case it is the regulated conformational flexibility that allows LHCs to switch between efficient light-harvesting and a photoprotective function.

scholarly journals Limitations to photosynthesis by proton motive force-induced photosystem II photodamage

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Geoffry A Davis ◽  
Atsuko Kanazawa ◽  
Mark Aurel Schöttler ◽  
Kaori Kohzuma ◽  
John E Froehlich ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Proton Motive Force ◽  
Motive Force ◽  
Limiting Factor ◽  
Wild Type ◽  
Recombination Rates ◽  
Atp Production ◽  
Photosynthetic Regulation ◽  
Light Capture

The thylakoid proton motive force (pmf) generated during photosynthesis is the essential driving force for ATP production; it is also a central regulator of light capture and electron transfer. We investigated the effects of elevated pmf on photosynthesis in a library of Arabidopsis thaliana mutants with altered rates of thylakoid lumen proton efflux, leading to a range of steady-state pmf extents. We observed the expected pmf-dependent alterations in photosynthetic regulation, but also strong effects on the rate of photosystem II (PSII) photodamage. Detailed analyses indicate this effect is related to an elevated electric field (Δψ) component of the pmf, rather than lumen acidification, which in vivo increased PSII charge recombination rates, producing singlet oxygen and subsequent photodamage. The effects are seen even in wild type plants, especially under fluctuating illumination, suggesting that Δψ-induced photodamage represents a previously unrecognized limiting factor for plant productivity under dynamic environmental conditions seen in the field.

scholarly journals Dynamics of the localization of the plastid terminal oxidase inside the chloroplast

2020 ◽  
Vol 71 (9) ◽  
pp. 2661-2669 ◽  
Author(s):  
Susanne Bolte ◽  
Elodie Marcon ◽  
Mélanie Jaunario ◽  
Lucas Moyet ◽  
Maité Paternostre ◽  
...  
Keyword(s):  
Thylakoid Membrane ◽  
Fluorescent Protein ◽  
Proton Motive Force ◽  
Motive Force ◽  
Terminal Oxidase ◽  
Valve Function ◽  
Partial Dissociation ◽  
Green Fluorescent ◽  
Plastid Terminal Oxidase

Abstract The plastid terminal oxidase (PTOX) is a plastohydroquinone:oxygen oxidoreductase that shares structural similarities with alternative oxidases (AOXs). Multiple roles have been attributed to PTOX, such as involvement in carotene desaturation, a safety valve function, participation in the processes of chlororespiration, and setting the redox poise for cyclic electron transport. PTOX activity has been previously shown to depend on its localization at the thylakoid membrane. Here we investigate the dynamics of PTOX localization dependent on the proton motive force. Infiltrating illuminated leaves with uncouplers led to a partial dissociation of PTOX from the thylakoid membrane. In vitro reconstitution experiments showed that the attachment of purified recombinant maltose-binding protein (MBP)–OsPTOX to liposomes and isolated thylakoid membranes was strongest at slightly alkaline pH values in the presence of lower millimolar concentrations of KCl or MgCl2. In Arabidopsis thaliana overexpressing green fluorescent protein (GFP)–PTOX, confocal microscopy images showed that PTOX formed distinct spots in chloroplasts of dark-adapted or uncoupler-treated leaves, while the protein was more equally distributed in a network-like structure in the light. We propose a dynamic PTOX association with the thylakoid membrane depending on the presence of a proton motive force.

scholarly journals Chaperone mediated coupling of subunit availability to activation of flagellar Type III Secretion

2020 ◽  
Author(s):  
Owain J. Bryant ◽  
Betty Y-W. Chung ◽  
Gillian M. Fraser
Keyword(s):  
Cell Membrane ◽  
Electric Potential ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Proton Motive Force ◽  
Secretion System ◽  
Motive Force ◽  
Type Iii

AbstractBacterial flagellar subunits are exported across the cell membrane by the flagellar Type III Secretion System (fT3SS), powered by the proton motive force (pmf) and a specialized ATPase that enables the flagellar export gate to utilise the pmf electric potential (ΔΨ). Export gate activation is mediated by the ATPase stalk, FliJ, but how this process is regulated to prevent wasteful dissipation of pmf in the absence of subunit cargo is not known. Here, we show that FliJ activation of the export gate is regulated by flagellar export chaperones. FliJ binds unladen chaperones and, using novel chaperone variants specifically defective for FliJ binding, we show that disruption of this interaction attenuates motility and cognate subunit export. We demonstrate in vitro that chaperones and the FlhA export gate component compete for binding to FliJ, and show in vivo that unladen chaperones, which would be present in the cell when subunit levels are low, sequester FliJ to prevent activation of the export gate and attenuate subunit export. Our data indicate a mechanism whereby chaperones couple availability of subunit cargo to pmf-driven export by the fT3SS.

In vivo regulation of thylakoid proton motive force in immature leaves

2018 ◽  
Vol 138 (2) ◽  
pp. 207-218 ◽  
Author(s):  
Wei Huang ◽  
Marjaana Suorsa ◽  
Shi-Bao Zhang
Keyword(s):  
Proton Motive Force ◽  
Motive Force
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