Bellafiore Stéphane, Barneche Frédy, Peltier Gilles, Rochaix Jean-David
Department of Molecular Biology, University of Geneva, 30, Quai Ernest Ansermet, 1211 Geneva, Switzerland.
Nature. 2005 Feb 24;433(7028):892-5. doi: 10.1038/nature03286.
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). 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 kinase; 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 Arabidopsis. 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.
光合生物能够通过状态转换来适应不断变化的光照条件，这一过程涉及光激发能量在光系统II（PSII）和光系统I（PSI）之间的重新分配。通过主要天线复合物（LHCII）在PSII和PSI之间的可逆结合，实现了这两个光系统光吸收能力的平衡（参考文献3）。相对于PSI，PSII的过度刺激会导致质体醌库的还原以及一种激酶的激活；LHCII的磷酸化；以及LHCII从PSII向PSI的转移（状态2）。PSI的过度刺激导致质体醌库的氧化会使这一过程逆转（状态1）。莱茵衣藻类囊体相关的丝氨酸-苏氨酸激酶Stt7是状态转换所必需的，在拟南芥中有一个名为STN7的同源物。我们在此表明，STN7的缺失会阻断状态转换和LHCII磷酸化。在stn7突变体植物中，质体醌库的还原程度更高，并且在不断变化的光照条件下生长受到损害，这表明STN7以及可能的状态转换在响应环境变化中具有重要作用。
