Role of the PsbS protein in Chlamydomonas reinhardtii

PsbS 蛋白在莱茵衣藻中的作用

• 批准号: 288499712
• 负责人: Professor Dr. Peter Jahns
• 金额: --
• 依托单位: Institut für Biochemie der Pflanzen
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/288499712?language=en
• 关键词: Role; PsbS; protein; Chlamydomonas; reinhardtii

Heat dissipation of excess excitation energy (NPQ) under high light(HL) is an important photoprotective mechanism active in allphotosynthetic organisms, which aims at the minimization of photooxidativedamage by reactive oxygen species. In land plants, thephotosystem II (PSII) protein PsbS plays a key role in NPQ regulation.PsbS acts as sensor of the lumen pH and by that controlsconformational changes in the PSII antenna, which are required forNPQ activation. In the green alga Chlamydomonas reinhardtii,LHCSR proteins act as pH-sensor and trigger NPQ activation. Here,NPQ activation is only possible after several hours of HL acclimationof the cells, which initiates the synthesis of LHCSR proteins. The roleof PsbS in C. reinhardtii is still unclear. During the past funding periodwe showed that PsbS is only transiently expressed during the first 4-8h of HL exposure and is rapidly degraded after about 24h of HLacclimation. PsbS localizes to thylakoid membranes and interacts withPSII. PsbS accumulation occurs in parallel with LHCSR accumulationand NPQ activation. Down-regulation of PsbS leads to reduction ofboth NPQ capacity and LHCSR accumulation. In the absence ofLHCSR protein, PsbS cannot compensate for the role of LHCSR inNPQ activation, and increased PsbS levels fail to increase the NPQcapacity. This indicates that PsbS is not essential for NPQ, butpossibly required for the establishment of a high NPQ capacity duringHL acclimation. We further accumulated evidence for a NPQindependentphotoprotective function of PsbS. The planned workaims at the goal to decipher the detailed function of PsbS in C.reinhardtii. To this end, the following central issues will be addressed:1) Generation of stable PSBS knockout lines by means of CRISPRCas9and characterization of their NPQ capacity and HL acclimationresponse. So far, we have analyzed only PsbS knock-down lines. 2)Determination of interaction partners and stoichiometry of PsbS andof LHCSR proteins. 3) Characterization of the PsbS degradationprocess and its impact on HL acclimation. 4) Characterization of thePsbS dynamics and of the HL acclimation response in mutantsaffected in qE-independent photoprotective mechanisms. 5)Determination of the PsbS dynamics and of HL acclimation inresponse to more natural fluctuating (high) light conditions. Most ofthe former studies on HL acclimation in C. reinhardtii have beenconducted with cells grown under non-natural permanent illuminationwithout intermittent dark periods. Inclusion of dark periods andapplication of fluctuating light intensities give reason to expect exciting information in terms of natural habitats, particularly regarding thedynamic of PsbS and LHCSR accumulation. The characterization ofmutants with defects in NPQ-independent photoprotectivemechanisms will further provide information about the integration ofPsbS into the photoprotective network of C. reinhardtii.

高光（HL）下过量激发能（NPQ）的散热是所有光合生物中活跃的重要光保护机制，其目的是最大限度地减少活性氧的光氧化损伤。在陆地植物中，光系统 II (PSII) 蛋白 PsbS 在 NPQ 调节中起着关键作用。PsbS 充当管腔 pH 值的传感器，并通过控制 PSII 天线的构象变化，这是 NPQ 激活所必需的。在绿藻莱茵衣藻中，LHCSR 蛋白充当 pH 传感器并触发 NPQ 激活。在这里，NPQ 激活只有在细胞 HL 适应几个小时后才有可能，从而启动 LHCSR 蛋白的合成。 PsbS 在莱茵衣藻中的作用仍不清楚。在过去的资助期间，我们表明 PsbS 仅在 HL 暴露的前 4-8 小时内短暂表达，并在 HL 适应约 24 小时后迅速降解。 PsbS 定位于类囊体膜并与 PSII 相互作用。 PsbS 积累与 LHCSR 积累和 NPQ 激活同时发生。 PsbS 的下调导致 NPQ 容量和 LHCSR 积累减少。在缺乏LHCSR蛋白的情况下，PsbS不能补偿LHCSR在NPQ激活中的作用，并且增加PsbS水平不能增加NPQ能力。这表明 PsbS 对于 NPQ 不是必需的，但可能是在 HL 驯化过程中建立高 NPQ 能力所必需的。我们进一步积累了 PsbS 不依赖于 NPQ 的光保护功能的证据。计划工作的目标是破译莱茵哈特氏菌中 PsbS 的详细功能。为此，将解决以下核心问题：1）通过CRISPRCas9生成稳定的PSBS敲除系，并表征其NPQ能力和HL驯化响应。到目前为止，我们仅分析了 PsbS 敲低品系。 2)确定PsbS和LHCSR蛋白的相互作用伙伴和化学计量。 3) PsbS 降解过程的表征及其对 HL 驯化的影响。 4) 受 qE 独立光保护机制影响的突变体中 PsbS 动力学和 HL 适应反应的表征。 5) 确定 PsbS 动力学和 HL 适应以响应更自然的波动（高）光照条件。以前大多数关于莱茵衣藻 HL 驯化的研究都是在没有间歇性黑暗期的非自然永久照明下生长的细胞进行的。黑暗时期的纳入和波动光强度的应用使我们有理由期待自然栖息地方面令人兴奋的信息，特别是关于 PsbS 和 LHCSR 积累的动态。具有 NPQ 独立光保护机制缺陷的突变体的表征将进一步提供有关 PsbS 整合到莱茵衣藻光保护网络中的信息。