The Cytochrome b6f Complex Is Not Involved in Cyanobacterial State Transitions
The Cytochrome b6f Complex Is Not Involved in Cyanobacterial State Transitions
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细胞色素 b(6)f 复合物不参与蓝藻状态转变
DOI：
10.1105/tpc.18.00916
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发表时间：
2019-04-01
期刊：
影响因子：
11.6
通讯作者：
Kirilovsky, Diana
中科院分区：
文献类型：
--
作者：
Calzadilla, Pablo, I;Zhan, Jiao;Kirilovsky, Diana
光合生物必须感知和响应波动的环境条件，以便进行有效的光合作用，并避免形成危险的活性氧。由于被吸收光的强度和光谱特性的变化，到达每个光系统的激发能会发生永久性的变化。蓝藻，像植物和藻类一样，已经发展出一种机制，称为“状态转换”，平衡光系统活动。在这里，我们以长聚球菌PCC 7942和聚囊球菌PCC 6803为模式生物，表征了细胞色素b(6)f复合物和磷酸化反应在蓝藻状态转变中的作用。首先，在状态II中观察到大的光系统II （PSII）荧光猝灭，这一结果似乎与从PSII到PSI的能量转移（溢出）无关。这种膜相关的过程被甜菜碱、硫酸和高浓度的磷酸盐所抑制。然后，使用不同的化学物质影响质体醌池氧化还原状态和细胞色素b(6)f活性，我们证明该复合物不参与S. elongatus或Synechocystis PCC6803的状态转变。最后，通过构建和表征21个蛋白激酶和磷酸酶突变体并使用化学抑制剂，我们证明磷酸化反应对蓝藻状态转变不是必需的。因此，蓝藻和植物（绿藻）状态转换的信号转导是完全不同的。
Photosynthetic organisms must sense and respond to fluctuating environmental conditions in order to perform efficient photosynthesis and to avoid the formation of dangerous reactive oxygen species. The excitation energy arriving at each photosystem permanently changes due to variations in the intensity and spectral properties of the absorbed light. Cyanobacteria, like plants and algae, have developed a mechanism, named "state transitions," that balances photosystem activities. Here, we characterize the role of the cytochrome b(6)f complex and phosphorylation reactions in cyanobacterial state transitions using Synechococcus elongatus PCC 7942 and Synechocystis PCC 6803 as model organisms. First, large photosystem II (PSII) fluorescence quenching was observed in State II, a result that does not appear to be related to energy transfer from PSII to PSI (spillover). This membrane-associated process was inhibited by betaine, Suc, and high concentrations of phosphate. Then, using different chemicals affecting the plastoquinone pool redox state and cytochrome b(6)f activity, we demonstrate that this complex is not involved in state transitions in S. elongatus or Synechocystis PCC6803. Finally, by constructing and characterizing 21 protein kinase and phosphatase mutants and using chemical inhibitors, we demonstrate that phosphorylation reactions are not essential for cyanobacterial state transitions. Thus, signal transduction is completely different in cyanobacterial and plant (green alga) state transitions.