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.

高光下过量激发能（NPQ）的热耗散是所有光合生物的一种重要的光保护机制，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调控中起关键作用。psb作为管腔pH值的传感器，通过控制PSII天线的构象变化，这是npq激活所必需的。在莱茵衣藻（Chlamydomonas reinhardtii）中，LHCSR蛋白作为ph传感器并触发NPQ激活。在这里，NPQ只有在细胞适应HL几个小时后才能激活，从而启动LHCSR蛋白的合成。psb在莱茵杆菌中的作用尚不清楚。在过去的资助期内，我们发现PsbS仅在HL暴露的前4-8小时内短暂表达，并在HL驯化约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激活并行发生。PsbS的下调导致NPQ容量和LHCSR积累的减少。在flhcsr蛋白缺失的情况下，PsbS不能补偿LHCSR激活inpq的作用，PsbS水平的增加不能增加npq容量。这表明PsbS对NPQ不是必需的，但可能是在hl驯化期间建立高NPQ能力所必需的。我们进一步积累了PsbS与npq无关的光保护功能的证据。计划中的工作旨在破译莱茵杆菌中psb的详细功能。为此，将解决以下核心问题：1)通过crisprcas9产生稳定的PSBS敲除系，并表征其NPQ能力和HL适应反应。到目前为止，我们只分析了psb的击穿线。2)确定PsbS和LHCSR蛋白的相互作用伙伴和化学计量学。3) PsbS降解过程特征及其对HL驯化的影响。4)不依赖于光保护机制的突变体psbs动态和HL驯化反应的表征。5)确定PsbS动态和HL对自然波动（高）光条件的适应。以往关于莱茵冷杉HL驯化的研究大多是在非自然永久光照下进行的，没有间歇性的暗期。包括暗期和波动光强的应用使我们有理由期待在自然栖息地方面获得令人兴奋的信息，特别是关于PsbS和LHCSR积累的动态。对不依赖npq的光保护机制缺陷突变体的研究将进一步提供psbs与莱因哈蒂青霉光保护网络整合的信息。