A megacomplex composed of both photosystem reaction centres in higher plants

Yokono, Makio; Takabayashi, Akira; Akimoto, Seiji; Tanaka, Ayumi

doi:10.1038/ncomms7675

Cited by 107 publications

(121 citation statements)

References 30 publications

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“…It has been proposed that, in the grana margin regions, which harbor LHCII and both photosystems, LHCII can migrate rapidly between them (Albertsson et al, 1990;Albertsson, 2001). This idea is supported by the recent discovery of mega complexes containing both photosystems in the grana margin regions (Yokono et al, 2015). Furthermore, phosphorylation of LHCII was found to increase not only the amount of PSI found in the grana margin region of thylakoid membranes (Tikkanen et al, 2008a), but also to modulate the pattern of PSI-PSII megacomplexes under changing light conditions .…”

supporting

confidence: 54%

Comparative Analysis of Light-Harvesting Antennae and State Transition in chlorina and cpSRP Mutants

Wang

Grimm

2016

Plant Physiol.

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State transitions in photosynthesis provide for the dynamic allocation of a mobile fraction of light-harvesting complex II (LHCII) to photosystem II (PSII) in state I and to photosystem I (PSI) in state II. In the state I-to-state II transition, LHCII is phosphorylated by STN7 and associates with PSI to favor absorption cross-section of PSI. Here, we used Arabidopsis (Arabidopsis thaliana) mutants with defects in chlorophyll (Chl) b biosynthesis or in the chloroplast signal recognition particle (cpSRP) machinery to study the flexible formation of PS-LHC supercomplexes. Intriguingly, we found that impaired Chl b biosynthesis in chlorina1-2 (ch1-2) led to preferentially stabilized LHCI rather than LHCII, while the contents of both LHCI and LHCII were equally depressed in the cpSRP43-deficient mutant (chaos). In view of recent findings on the modified state transitions in LHCI-deficient mutants (Benson et al., 2015), the ch1-2 and chaos mutants were used to assess the influence of varying LHCI/LHCII antenna size on state transitions. Under state II conditions, LHCII-PSI supercomplexes were not formed in both ch1-2 and chaos plants. LHCII phosphorylation was drastically reduced in ch1-2, and the inactivation of STN7 correlates with the lack of state transitions. In contrast, phosphorylated LHCII in chaos was observed to be exclusively associated with PSII complexes, indicating a lack of mobile LHCII in chaos. Thus, the comparative analysis of ch1-2 and chaos mutants provides new evidence for the flexible organization of LHCs and enhances our understanding of the reversible allocation of LHCII to the two photosystems.

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supporting

confidence: 54%

Comparative Analysis of Light-Harvesting Antennae and State Transition in chlorina and cpSRP Mutants

Wang

Grimm

2016

Plant Physiol.

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“…However, Lhcb1 is more phosphorylated in large PSII-rich supercomplexes solubilized with digitonin from stromal lamellae and grana margins, whereas its level of phosphorylation in PSII-LHCII supercomplexes extracted with b-DM from grana cores is comparatively low (Fig. 6; Yokono et al, 2015). These observations suggest that Lhcb phosphorylation may contribute to the movement of the PSII-LHCII supercomplexes from grana cores toward lessstacked domains of the thylakoid membrane, grana margins, and stromal lamellae.…”

Section: Antenna Phosphorylation In the Psii-lhcii Supercomplexesmentioning

confidence: 60%

“…A relatively high level of Lhcb1 and Lhcb2 phosphorylation was observed in the Sc4b band and in the Mc5b band. Both were described to contain PSI, PSII, and LHCII, but fluorescence lifetime analysis indicated that PSII may not be functionally connected to PSI in these bands (Järvi et al, 2011;Yokono et al, 2015).…”

Section: Phosphorylation Of Antenna Isoforms In Different Supercomplexesmentioning

confidence: 99%

Phosphorylation of the Lhcb2 isoform of Light Harvesting Complex II is central to state transitions

et al. 2015

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ORCID IDs: 0000-0003-0587-7621 (P.L.); 0000-0002-6155-9153 (D.D.).Light-harvesting complex II (LHCII) is a crucial component of the photosynthetic machinery, with central roles in light capture and acclimation to changing light. The association of an LHCII trimer with PSI in the PSI-LHCII supercomplex is strictly dependent on LHCII phosphorylation mediated by the kinase STATE TRANSITION7, and is directly related to the light acclimation process called state transitions. In Arabidopsis (Arabidopsis thaliana), the LHCII trimers contain isoforms that belong to three classes: Lhcb1, Lhcb2, and Lhcb3. Only Lhcb1 and Lhcb2 can be phosphorylated in the N-terminal region. Here, we present an improved Phos-tag-based method to determine the absolute extent of phosphorylation of Lhcb1 and Lhcb2. Both classes show very similar phosphorylation kinetics during state transition. Nevertheless, only Lhcb2 is extensively phosphorylated (.98%) in PSI-LHCII, whereas phosphorylated Lhcb1 is largely excluded from this supercomplex. Both isoforms are phosphorylated to different extents in other photosystem supercomplexes and in different domains of the thylakoid membranes. The data imply that, despite their high sequence similarity, differential phosphorylation of Lhcb1 and Lhcb2 plays contrasting roles in light acclimation of photosynthesis.

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“…Moreover, the traditionalstate transition model is based on lateral segregation of PSII-LHCII and PSI-LHCI to different thylakoid domains. It, however, seems likely that PSII and PSI are energetically connected through a shared light-harvesting system composed of LHCII trimers (Grieco et al, 2015), and there is efficient excitation energy transfer between the two photosystems (Yokono et al, 2015). Nevertheless, it is clear that LHCII phosphorylation is a prerequisite to form an isolatable PSI-LHCII complex called the state transition complex (Pesaresi et al, 2009;Järvi et al, 2011).…”

mentioning

confidence: 98%

Plants Actively Avoid State Transitions upon Changes in Light Intensity: Role of Light-Harvesting Complex II Protein Dephosphorylation in High Light

et al. 2015

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ORCID IDs: 0000-0002-6309-5532 (N.R.M.); 0000-0002-2753-9597 (M.T.).Photosystem II (PSII) core and light-harvesting complex II (LHCII) proteins in plant chloroplasts undergo reversible phosphorylation upon changes in light intensity (being under control of redox-regulated STN7 and STN8 kinases and TAP38/PPH1 and PSII core phosphatases). Shift of plants from growth light to high light results in an increase of PSII core phosphorylation, whereas LHCII phosphorylation concomitantly decreases. Exactly the opposite takes place when plants are shifted to lower light intensity. Despite distinct changes occurring in thylakoid protein phosphorylation upon light intensity changes, the excitation balance between PSII and photosystem I remains unchanged. This differs drastically from the canonical-state transition model induced by artificial states 1 and 2 lights that concomitantly either dephosphorylate or phosphorylate, respectively, both the PSII core and LHCII phosphoproteins. Analysis of the kinase and phosphatase mutants revealed that TAP38/PPH1 phosphatase is crucial in preventing state transition upon increase in light intensity. Indeed, tap38/pph1 mutant revealed strong concomitant phosphorylation of both the PSII core and LHCII proteins upon transfer to high light, thus resembling the wild type under state 2 light. Coordinated function of thylakoid protein kinases and phosphatases is shown to secure balanced excitation energy for both photosystems by preventing state transitions upon changes in light intensity. Moreover, PROTON GRADIENT REGULATION5 (PGR5) is required for proper regulation of thylakoid protein kinases and phosphatases, and the pgr5 mutant mimics phenotypes of tap38/pph1. This shows that there is a close cooperation between the redox-and proton gradient-dependent regulatory mechanisms for proper function of the photosynthetic machinery.

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A megacomplex composed of both photosystem reaction centres in higher plants

Cited by 107 publications

References 30 publications

Comparative Analysis of Light-Harvesting Antennae and State Transition in chlorina and cpSRP Mutants

Comparative Analysis of Light-Harvesting Antennae and State Transition in chlorina and cpSRP Mutants

Phosphorylation of the Lhcb2 isoform of Light Harvesting Complex II is central to state transitions

Plants Actively Avoid State Transitions upon Changes in Light Intensity: Role of Light-Harvesting Complex II Protein Dephosphorylation in High Light

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