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State transitions and light adaptation require chloroplast thylakoid protein kinase STN7


Photosynthetic organisms are able to adjust to changing light conditions through state transitions, a process that involves the redistribution of light excitation energy between photosystem II (PSII) and photosystem I (PSI)1,2. Balancing of the light absorption capacity of these two photosystems is achieved through the reversible association of the major antenna complex (LHCII) between PSII and PSI (ref. 3). Excess stimulation of PSII relative to PSI leads to the reduction of the plastoquinone pool and the activation of a kinase4,5; the phosphorylation of LHCII; and the displacement of LHCII from PSII to PSI (state 2). Oxidation of the plastoquinone pool by excess stimulation of PSI reverses this process (state 1). The Chlamydomonas thylakoid-associated Ser-Thr kinase Stt7, which is required for state transitions, has an orthologue named STN7 in Arabidopsis6. Here we show that loss of STN7 blocks state transitions and LHCII phosphorylation. In stn7 mutant plants the plastoquinone pool is more reduced and growth is impaired under changing light conditions, indicating that STN7, and probably state transitions, have an important role in response to environmental changes.

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Figure 1: The STN7 protein kinase of Arabidopsis is required for state transitions.
Figure 2: Phosphorylation of LHCII is diminished in stn7 under state 2 conditions.
Figure 3: Measurements of photosynthetic parameters for stn7 detached leaves.
Figure 4: Growth of the stn7 mutant is impaired under changing light conditions.

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We thank N. Roggli for drawings; C. Niyogi and M. Havaux for the npq4 mutant; C. Fankhauser for transformation vectors and help with Arabidopsis; C. Bréhélin and F. Kessler (Plant Survival NCCR) for help with the protoplast transformation experiments; B. Genty and M. Goldschmidt-Clermont for discussions; M. Péan, A. Beyly and the GRAP team (CEA Cadarache) for support in growing plants under controlled conditions; and B. Delessert for assistance in the phytotron. F.B. was supported by a long-term EMBO fellowship. This work was supported by a grant from the Swiss National Foundation.

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Correspondence to Jean-David Rochaix.

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Supplementary information

Supplementary Figure 1

Locations of T-DNA insertions in STN7 (At1g68830) and STN8 (At5g01020) and RT-PCR of STN7 and STN8 transcripts in the wild-type (Col-0), stn7, stn8 and in the rescued stn7-1R, stn7-4R, stn8-13 and stn8-69 lines. (PDF 134 kb)

Supplementary Figure 2

The STN7 kinase is localized in chloroplast membranes. (PDF 577 kb)

Supplementary Figure 3

Immunoblot analysis of proteins of the photosynthetic apparatus. (PDF 137 kb)

Supplementary Data

This file contains additional Methods, references and legends for Supplementary Figures 1-3. (DOC 66 kb)

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Bellafiore, S., Barneche, F., Peltier, G. et al. State transitions and light adaptation require chloroplast thylakoid protein kinase STN7. Nature 433, 892–895 (2005).

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