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Structure and dynamics of the thylakoid membrane









Kavli Royal Society Centre, Chicheley Hall, Newport Pagnell, Buckinghamshire, MK16 9JJ


Theo Murphy international scientific meeting organised by Professor James Barber FRS and Professor Peter Horton FRS

Event details

We have a remarkable understanding of the various thylakoid membrane protein complexes which constitute the photosynthetic electron transfer chain of plants. We now need to integrate this knowledge to describe the structure and function of the complete thylakoid membrane and understanding how it is regulated to optimise photosynthetic efficiency in response to changing environments.

Biographies of the organisers and speakers are available below. Audio recordings are freely available and the programme can be downloaded here. Papers have been been published in an issue of Philosophical Transactions of the Royal Society B.

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Schedule of talks

Session 1: Structure, mechanisms and organisation of protein complexes in thylakoids

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Dynamic lateral heterogeneity of plant thylakoid protein complexes

Dr Jan Anderson, University of Auckland, NZ


The concept that in photosynthesis two photosystems cooperate in series, immortalised in Hill and Bendall’s (1960) Z scheme, was still a black box defining neither structural nor the molecular organization of the photosystems within thylakoids. Digitonin  fragmentation of  isolated chloroplasts, followed by differential centrifugation, yielded a heavier granal fraction enriched in PSII which bound a third “enigmatic” cytochrome b-559, and a lighter PSI fraction, proving that indeed there were two photosystems.  The differentiation of the continuous thylakoid membrane network into grana and stroma thylakoids is a morphological reflection of the non-random distribution of PSII and PSI and ATP synthase, which became known as lateral heterogeneity. Long-term acclimation of sun versus shade plants modulates the composition and function and membrane appression of thylakoids. Significantly, highly dynamic rapid grana-stacking/ destacking, with reversible macro-organization of PSII/LHCII supercomplex arrays within grana optimise photosynthetic function in vivo over the entire range of irradiance; this still poses a grana conundrum.

Wah Soon Chow, Australian National University, Australia

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Electron cryo-tomography of membrane protein complexes in mitochondria and chloroplasts

Professor Werner Kühlbrandt, Max-Planck-Institute of Biophysics, Germany


Electron crystallography of two-dimensional (2D) crystals makes it possible to examine membrane proteins in the quasi-native environment of a lipid bilayer at high to moderately high resolution. Recently, we have used electron crystallography to investigate functionally important conformational changes in membrane transport proteins such as the sodium/proton antiporters NhaA and NhaP, or the structure of channelrhodopsin.

“Single particle” cryo-EM is well suited to study the structure of large macromolecular assemblies in the 3.2 to 20Å resolution range.  A recent example is our 19Å map of a mitochondrial respiratory chain supercomplex consisting of one copy of complex 1, two copies of complex III, and one of complex IV.  The fit of the x-ray structures to our map indicates short pathways for efficient electron shuttling between complex I and III by ubiquinol, and between complex III and IV by cytochrome c.

Electron cryo-tomography can visualize large protein complexes in their cellular context at 30-50Å resolution, bridging the gap between protein crystallography and light microscopy. Cryo-ET is particularly suitable for studying biological membranes and large membrane protein complexes in situ. Cryo-ET of chloroplast thylakoids revealed the ATP synthase in flat stromal membranes and grana end membranes. We also could localize photosystem-II dimers in stacked and unstacked grana membranes.  Together with the high-resolution structure of LHC-II, this enabled us to build a molecular model of membrane interaction in chloroplast grana. 

In mitochondria of 6 different species we studied (2 mammals, 3 fungi, 1 plant), we found long rows of ATP synthase dimers along the tightly curved cristae ridges, whereas it is always monomeric and confined to flat membrane regions in chloroplasts. The proton pumps of the mitochondrial respiratory chain seemed to be confined to the flat membrane regions on either side of the dimer rows. This highly conserved arrangement appears to be a fundamental feature of all mitochondria from healthy cells, and suggests a fundamental role of the mitochondrial cristae as proton traps for efficient ATP synthesis.  Interestingly, the inner membrane of mitochondria from the aging model organism Podospora anserina, a filamentous fungus with a fixed life span of ~20 days, undergoes a dramatic change as the cells age, and the dimer rows break up.


Goswami P, Paulino C, Hizlan D, Vonck J, Yildiz Ö, Kühlbrandt W  (2010) Structure of the archaeal Na+/H+ antiporter NhaP1 and functional role of transmembrane helix 1. EMBO J. 30, 439-449.

Strauss M, Hofhaus G, Schröder R R, Kühlbrandt W (2008) Dimer ribbons of ATP synthase shape the inner mitochondrial membrane. EMBO J 27, 1154-1160.

Single-particle analysis:
Gipson P, Mills D, Wouts R, Grininger M, Vonck J, Kühlbrandt W (2010): 
Direct structural insight into the substrate-shuttling mechanism of yeast fatty acid synthase by electron cryomicroscopy. 
Proc Natl Acad Sci USA107, 9164-9169

Electron crystallography:
Kühlbrandt W, Wang DN, Fujiyoshi Y (1994): 
Atomic model of plant light-harvesting complex by electron crystallography. Nature367, 614-621.      

Appel M, Hizlan D, Vinothkumar KR, Ziegler C and Kühlbrandt W (2009): 
Conformations of NhaA, the Na+/H+ exchanger from Escherichia coli, in the pH-activated and ion-translocating states.
J Mol Biol388, 659-672.

Electron cryo-tomography:
Strauss M, Hofhaus G, Schröder RR, Kühlbrandt W (2008):
Dimer ribbons of ATP synthase shape the inner mitochondrial membrane.
EMBO J27, 1154-1160.

Daum B, Nicastro D, Austin II J, McIntosh JR, Kühlbrandt W (2010): 
Arrangement of photosystem-II and ATP synthase in chloroplast membranes of spinach and pea. 
Plant Cell22, 1299-1312.

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How ATP synthase works

Professor Sir John Walker FRS, The Medical Research Council, UK


The ATP synthase found in chloroplasts has many features in common with the ATP synthases found in eubacteria and mitochondria. Their overall architectures are similar, and they all consist of two rotary motors linked by a stator and a flexible rotor. When rotation of the membrane bound rotor is driven by proton motive force, the direction of rotation ensures that ATP is made from ADP and phosphate in the globular catalytic domain. When ATP serves as the source of energy and is hydrolysed in the catalytic domain, the rotor turns in the opposite sense and protons are pumped outwards through the membrane domain, and away from the catalytic domain. The lecture will describe the common features of their catalytic mechanisms. However, the ATP synthase from chloroplasts, eubacteria and mitochondria differ in several key features, in their mechanisms of regulation and most fundamentally in the energy cost that is paid to make an ATP molecule. The most efficient ATP synthase is found in the mitochondria from multicellular animals. The ATP synthases in unicellular organisms, and chloroplasts, pay various higher costs that seem to reflect the supply of available energy.

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Lipid functions in cytochrome bc complexes; an odd event in evolution

Professor William Cramer, Purdue University, USA


Lipid binding sites and properties were compared in the hetero-oligomeric cytochrome b6f and bc1 complexes that function in photosynthetic and respiratory membrane energy transduction.  Seven lipid binding sites in the cyanobacterial b6f complex overlap three natural sites in the Chlamydomonasreinhardtii algal complex and four sites in the yeast mitochondrial bc1 complex.  Inferences of lipid binding sites and functions are supported by sequence, interatomic distance, and B-factor information on interacting lipid groups and coordinating amino acid residues. Lipid functions in the b6f complex include the consequence of substitution of the eighth (‘H’) trans-membrane helix present in the mitochondrial cytochrome b subunit by a lipid and chlorin ring in b6f. The question of the function of this lipid substitution is of interest. The quinol oxidation site is on the p- (lumenal) side of the ‘H’ helix or the substituted lipid. Oxidation of PQH2 is coupled to the n (stromal)-side activation of an LHC kinase.  It is suggested that the presence of the lipid may enable the trans-membrane signaling that activates the kinase. (Support from NIH GM-038323). 

S S Hasan, Purdue University, USA
E Yamashita, Osaka University, Japan

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Photosystem II structure and function: successes and challenges.

Professor James Barber FRS, Imperial College London, UK


It was the work of Jan Anderson, together with Keith Boardman (1) that showed it was possible to physically separate Photosystem I (PSI) from Photosysten II (PSII)  and later it was Jan Anderson (2) who realised the importance of this work in terms of the fluid-mosaic model as applied to the thylakoid membrane. Since then there has been a steady progress in the development of biochemical procedures to isolate both PSII and PSI for physical, biochemical, molecular biological and structural studies, culminating in their crystallization and structural determination at atomic resolution. There are crystal structures for PSII and PSI isolated from cyanobacteria (3,4,5,6) and for PSI   from higher plants (7). In the case of higher plants, the biochemical procedures developed have built on the recognition that PSII and PSI are lateral separated between granal and stromal regions as proposed by Jan Anderson and Bertil Andersson (8)

The structure of the cyanobacterial PSII has now been resolved to 1.9A (5). It is a dimer having a molecular mass of 700 kDa and the crystal structures have provided  organisational details of  the 19/20 subunits (16/17 intrinsic and 3 extrinsic) which make up each monomer and revealed information about the position and protein environments of  the cofactors involved in the absorption of light, charge separation and water splitting. This level of detail has yet to be elucidated for higher plant PSII especially important because there are a number of significant differences between  PSII of cyanobacteria and that of higher plants including differences in core subunits composition (both intrinsic and extrinsic) and light harvesting systems (Chla/Chlb binding proteins in plants and phycobilisomes in cyanobacteria). Progress towards this end will be presented.

1.         Boardman, N K & Anderson, J M.  1964 Isolation from spinach chloroplasts of particles containing different proportions of chlorophyll a and chlorophyll b and their possible role in the light reactions of photosynthesis. Nature 203, 166-167.
2.         Anderson, J M.  1975 The molecular organization of chloroplast thylakoids. Biochim  Biophys  Acta 416, 191-235.
3.         Ferreira, K N, Iverson, T M, Maghlaoui, K, Barber J &  Iwata, S. 2004 Architecture of the photosynthetic oxygen evolving center. Science 303, 1831–1838. 
4.         Loll, B, Kern, J, Saenger, W, Zouni, A & Biesiadka, J. 2005 Towards complete cofactor arrangement in the 3.0 Å resolution structure of photosystem II. Nature 438, 1040–1044. 
5          Umena, Y, Kawakami, K, Shen, J R & Kamiya, N. 2011 Crystal structure of oxygen-evolving photosystem II at a resolution of 1.9 Å. Nature 473, 55–60.
6.         Jordan, P, Fromme, P, Witt, H T, Klukas, O, Saenger, W & Krauß, N. 2001 Three-dimensional structure of cyanobacterial photosystem I at 2.5 Å resolution. Nature 411, 909–917.
7.         Amunts, A, Drory, O & Nelson, N. 2007 The structure of a plant photosystem I supercomplex at 3.4 Å resolution. Nature 447, 58–63.
8.         Andersson, B & Anderson, J M. 1980 Lateral heterogeneity in the distribution of chlorophyll protein complexes of the thylakoid membranes of spinach chloroplasts. Biochim Biophys Acta 593, 427–440.

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Structure, function, evolution and utilization of photosystem I

Professor Nathan Nelson, Tel Aviv University, Israel


Abstract not yet available.

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Structure of the dimeric RC-LH1 complex from Rhodobaca bororiensis studied by electron microscopy

Professor Egbert Boekema, Groningen University, The Netherlands


Electron microscopy and single particle averaging are important tools to investigate structures of large membrane proteins. For instance, supercomplexes of plant thylakoid membranes and inner mitochondrial membranes are a popular topic. In this contribution, we performed an investigation on isolated RC-LH1 complexes of Rhodobaca with the aim of establishing the peripheral antenna conformation, and in particular the structural role of PufX. Rhodobaca is an alkaliphilic purple nonsulfur bacterium found in African Rift valley soda lakes [Milford 2000]. Projection maps of dimeric complexes were obtained at 13 Å resolution and show the positions of the α-helices of 2x14 LH1 units subunits. They are organized in two half-rings of 2 x 13 units. In addition, there are two units in the interface of the two halves of the dimer. Between the interface and the two half rings are two openings on each side. Next to the openings there are additional densities present, considered to be occupied by in total 4 PufX molecules. The model differs from previously proposed configurations for other purple bacteria, in which the LH1 ribbon is continuous, but with two openings at the end and in which the dimeric RC-LH1 complex contains only two PufX molecules.

Milford, A D, Achenbach, L A, Jung, D O and Madigan, M T (2000) Rhodobaca bogoriensis gen nov and sp nov, an alkaliphilic purple nonsulfur bacterium from African Rift Valley soda lakes. Arch Microbiol 174, 18-27

Dmitry A Semchonok, University of Groningen, The Netherlands
Colette Jungas, CEA, DSV, IBEB, Laboratoire de Biologie Cellulaire and CNRS, UMR Biologie Végétale et Microbiologie Environnementales/Université Aix-Marseille,  France

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Session 2: Dynamics of thylakoids: regulation, assembly and response to the environment

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How is Photosystem I protected against photodamage?

Professor Eva-Mari Aro, University of Turku, Finland


In sharp contrast to constant photodamage to PSII, the PSI centers are very efficiently protected against light damage, and in rare cases of damage to PSI, the subsequent recovery occurs very slowly. However, it was recently demonstrated that high light illumination can be very dangerous also to PSI. This occurs when the amount of electrons fed to the electron transfer chain (ETC) by PSII exceeds the capacity of electron acceptors on the reducing side of PSI. Plants have a capacity to regulate the relative reducing efficiencies of PSII and PSI by several different means. These include (i) the control of relative excitation of PSII and PSI, (ii) the regulation of the speed of electron transfer via the Cyt b6f complex, and (iii) the tuning of the amount of active PSII reaction centers. We have recently shown, by using the pgr5 mutant, that in the absence of the proton gradient dependent control of Cyt b6f, the PSI centers are very sensitive to photoinhibition. Likewise, we have shown that an accumulation in the stn7 mutant of excess electrons in intersystem ETC under low light, due to an excitation unbalance of the photosystems, is very harmful to PSI upon subsequent exposure of leaves to high light. These findings have prompted us to develop new hypotheses and theories concerning the photosensitivity of the photosynthetic apparatus and the mechanisms developed during evolution to protect the photosynthetic apparatus against photodamage.  We consider highly probable that decreasing the PSII activity upon photoinhibition is a mechanism that has developed to protect PSI against photodamage upon prolonged high light stress or under fluctuating light conditions. We will discuss about the relationships between PSII turnover, thermal dissipation of excitation energy, regulation of excitation energy distribution between PSII and PSI and the regulation of electron transfer in order to broaden the current picture on photoprotection of photosynthesis.

Marjaana Suorsa, Sari Sirpiö, Michele Grieco, Markus Nurmi and Mikko Tikkanen, University of Turku, Finland

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Optimisation of light harvesting and photoprotection – molecular mechanisms and physiological consequences

Professor Peter Horton FRS, Sheffield University, UK


The distinctive lateral organisation of the protein complexes in the thylakoid membrane discovered by Jan Anderson and colleagues is dependent of the balance of various attractive and repulsive forces.  Modulation of these forces allows critical physiological regulation of photosynthesis to provide efficiency light harvesting in limiting light but dissipate excess potentially damaging radiation in saturating light.  The light harvesting complexes (LHCII) are central to this regulation, which is achieved by phosphorylation of stromal residues, protonation on the lumen surface and de-epoxidation of bound violaxanthin.  The functional flexibility of LHCII derives from a remarkable pigment composition and configuration which not only allow efficient absorption of light and efficient energy transfer either to PSII or PSI core complexes, but through subtle configurational changes can also exhibit highly efficient dissipative reactions involving chlorophyll-xanthophyll and/or chlorophyll-chlorophyll interactions.  These changes in function are determined at a macroscopic level by alterations in protein-protein interactions in the thylakoid membrane. The capacity and dynamics of this regulation are tuned to different physiological scenarios by the exact protein and pigment content of the light harvesting system. In this presentation the molecular mechanisms involved will be reviewed, and the optimisation of the light harvesting system in different environmental conditions described.

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Role of protein kinases and phosphatases involved in the acclimation of the photosynthetic apparatus

Professor Jean-David Rochaix, University of Geneva, Switzerland


Photosynthetic organisms are subjected to frequent changes in light quality and quantity and need to respond accordingly. These acclimatory processes are mediated to a large extent through thylakoid protein phosphorylation. Recently two major thylakoid protein kinases have been identified and characterized. The Stt7/STN7/ kinase is mainly involved in the phosphorylation of the LHCII antenna proteins and required for state transitions. It is firmly associated with the cytochrome b6f complex and its activity is regulated by the redox state of the plastoquinone pool. The other kinase, Stl1/STN8 is responsible for the phosphorylation of the PSII core proteins. Using a reverse genetics approach we have recently identified two chloroplast protein phosphatases, PPH1/TAP38 and PBCP which counteract the activity of STN7 and STN8, respectively. Both belong to the PP2C-type phosphatase family and are conserved in land plants and algae. PBCP influences the same processes as the STN8 kinase, thylakoid membrane folding and turnover of the PSII core protein D1. The picture which emerges from these studies is that of a complex regulatory network of chloroplast protein kinases and phosphatases which is involved in light acclimation, in maintenance of the plastoquinone redox poise under fluctuating light, in the control of thylakoid protein turnover and in the adjustment to metabolic needs.

Sylvain Lemeille, Alexey Shapiguzov, Iga Samol, Geoffrey Fucile, Adrian Willig and  Michel Goldschmidt-Clermont, University of Geneva, Switzerland

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Subunit organisation of the thylakoid protease involved in D1 degradation during Photosystem II repair

Professor Peter J Nixon, Imperial College London, UK


Despite the existence of multiple photoprotective mechanisms in vivo, visible light will ultimately cause fatal and irreversible damage to the Photosystem II (PSII) complex (so-called chronic photoinhibition).  Damaged PSII can, however, be repaired through the operation of a ‘PSII repair cycle’, which involves partial disassembly of the damaged PSII complex and the selective replacement of the damaged subunit (predominantly the D1 subunit) by a newly synthesised copy and reassembly. A key area of current research is to understand how damaged D1 is recognised and removed from the thylakoid membrane. Our recent experimental data support a model in which D1 is degraded in the cyanobacterium Synechocystis sp. PCC 6803 by a hetero-oligomeric complex composed of two different types of FtsH subunit (FtsH2 and FtsH3), with degradation proceeding from the N-terminus of D1 in a highly processive reaction [1]. We postulate that a similar mechanism of D1 degradation also operates in chloroplasts. Deg proteases are not required for D1 degradation in Synechocystis 6803 but members of this protease family appear to play a supplementary role in D1 degradation in chloroplasts.

[1] Komenda, J, Sobotka, R and Nixon, P J (2012) Assembling and maintaining the Photosystem II complex in chloroplasts and cyanobacteria. Curr Opin Plant Biol

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Session 3: Responses to environmental changes

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Acclimation of leaves to low light produces large grana: the origin of the predominant attractive force at work

Professor Wah Soon Chow, The Australian National University, Australia


Photosynthetic membrane sacs (thylakoids) of plants form granal stacks interconnected by non-stacked thylakoids, thereby being able to fine-tune photosynthesis.  Growth in low light leads to the formation of large grana, which sometimes contain as many as 160 thylakoids.  The net surface charge of thylakoid membranes is negative, even in low-light-grown plants, so an attractive force is required to overcome the electrostatic repulsion.  The theoretical van der Waals attraction is, however, at least 20-fold too small to play the role.  We determined the enthalpy change, in the spontaneous stacking of previously unstacked thylakoids on addition of Mg2+, to be zero or marginally positive (endothermic).  The Gibbs free energy change for the spontaneous process is necessarily negative; therefore, an increase in entropy is the only way to achieve such a negative Gibbs free energy change.  We conclude that the dominant attractive force in thylakoid stacking is entropy-driven.  Some mechanisms for increasing entropy upon stacking of thylakoid membranes, particularly in low-light plants, are discussed.

Husen Jia, John R Liggins, The Australian National University, Australia

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Cellular redox homeostasis and regulation of gene expression

Professor Christine Foyer, University of Leeds, UK


Cellular redox homeostasis is a hub for signal integration. Interactions between redox metabolism and the ABSCISIC ACID (ABA)-INSENSITIVE-4 (ABI4) transcription factor were characterised in the Arabidopsis thaliana VITAMIN C DEFECTIVE 1 (vtc1)and VITAMIN C DEFECTIVE 2 (vtc2) mutants, which are defective in ascorbic acid synthesis and show a slow growth phenotype together with enhanced ABA levels relative to the wild type (Col0). The 75% decrease in the leaf ascorbate pool in the vtc2 mutants was not sufficient to adversely affect GA metabolism. The transcriptome signatures of the abi4, vtc1 and vtc2 mutants showed significant overlap, with a large number of transcription factors or signaling components similarly repressed or induced. Moreover, lincomycin-dependent changes in LIGHT HARVESTING CHLOROPHYLL A/B BINDING PROTEIN 1.1 (LHCB1.1) expression were comparable in these mutants, suggesting overlapping participation in chloroplast to nucleus signaling. The slow growth phenotype of vtc2 was absent in the abi4 vtc2 double mutant, as was the sugar insensitive phenotype of the abi4 mutant. Octadecanoid derivative-responsive AP2/ERF-domain transcription factor 47 (ORA47) and AP3 (an ABI5-binding factor) transcripts were enhanced in vtc2 but repressed in abi4 vtc2, suggesting that ABI4 and ascorbate modulate growth and defence gene expression through jasmonate signalling.

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From ecophysiology to phenomics: some implications of photoprotection and shade-sun acclimation in-situ for dynamics of thylakoids in-vitro

Professor Charles Barry Osmond FRS, The Australian National University and University of Wollongong, Australia


Ever since the pioneering studies of shade-sun acclimation in-vivo (Björkman & Holmgren 1963), the discovery of huge grana in the shade plant Alocasia (Goodchild et al 1972) and analyses of electron transport in thylakoid membranes of isolated pea chloroplasts in response to light intensities during growth (Leong & Anderson 1984), physiological studies in diverse plants have presented reality checks for contemporary understanding of the dynamics of these membrane systems. This paper presents new physiological data from in-vivo chlorophyll fluorescence analyses on the time frames of the slow coordinated photosynthetic development of sink leaves, and on slow renovation of photosynthetic properties of old leaves during sun to shade and shade to sun acclimation in the canopies of woody plants. It also focuses on pigment dynamics in relation to photoprotection in avocado, especially those encouraging further attention to the role of lutein epoxide and lutein in light harvesting and photoprotection in shade leaves. In so doing it grapples with issues in-vivo that seem relevant to our increasingly sophisticated understanding of ΔpH-dependent, xanthophyll pigment stabilized non-photochemical quenching (NPQ) in the antennae of PSII in thylakoid membranes in-vitro. 

Britta Förster, The Australian National University, Australia
Shizue Matsubara, IBG-2: Pflanzenwissenschaften, Forschungszentrum Jülich, Germany
Melinda Waterman, University of Wollongong, Australia
Brian E S Gunning, The Australian National University, Australia
Barry J Pogson, The Australian National University, Australia

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The regulatory factors for the biogenesis of thylakoid membrane protein complexes: diverse or conservative?

Professor Lixin Zhang, Institute of Botany, Chinese Academy of Sciences, China


The major multiprotein photosynthetic complexes, located in thylakoid membranes, are responsible for the capture of light and its conversion to chemical energy in oxygenic photosynthesis organisms. Although the structure and function of these protein complexes for oxygenic photosynthesis have been extensively explored, the molecular mechanisms underlying the biogenesis and assembly of thylakoid protein complexes still remain elusive. In this review, we summarized the present knowledge regarding the regulatory components identified to be involved in the biogenesis of thylakoid protein complexes in photosynthetic organisms. The functions and their conservative mechanisms in thylakoid membrane protein complex biogenesis are discussed. Based on a wealth of information greatly benefited from the studies through genetic, transcriptomic and proteomic approaches, we attempt to integrate the well-established functions of those regulatory factors into the evolution of the structure and components of thylakoid protein complexes.

Wei Chi, Chinese Academy of Sciences, China

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The role of GOLDEN2-LIKE transcription factors in thylakoid assembly

Professor Jane Langdale, University of Oxford, UK


GOLDEN2-LIKE transcription factors are required for normal chloroplast development in land plant species that encompass the range from bryophytes to angiosperms. The most obvious morphological defect in loss of function glk mutant plants is a failure to assemble thylakoids appropriately. In the flowering plant Arabidopsis thaliana, GLK proteins synchronously upregulate genes relating to light harvesting and chlorophyll biosynthesis, via direct interaction with promoter sequences. We have thus proposed that GLK activity optimizes photosynthesis by co-ordinating responses to variable environmental conditions. The direct connection between GLK activity and thylakoid assembly has yet to be established but intriguing differences between GLK function in C3 and C4 photosynthesising plants have led us to propose an evolutionary trajectory for GLK function.

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Structure and dynamics of the thylakoid membrane Kavli Royal Society Centre, Chicheley Hall Newport Pagnell Buckinghamshire MK16 9JJ