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 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 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’.

scholarly journals A bestrophin-like protein modulates the proton motive force across the thylakoid membrane in Arabidopsis

2016 ◽  
Vol 58 (10) ◽  
pp. 848-858 ◽  
Author(s):  
Zhikun Duan ◽  
Fanna Kong ◽  
Lin Zhang ◽  
Wenjing Li ◽  
Jiao Zhang ◽  
...  
Keyword(s):  
Thylakoid Membrane ◽  
Proton Motive Force ◽  
Motive Force
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