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.

在高光（HL）下，过量激发能量（NPQ）的热量耗散是在全球体生物体中活跃的重要光保护机制，其目的是通过活性氧对光氧化剂量最小化。在陆地植物中，Photosystem II（PSII）蛋白PSB在NPQ调节中起关键作用。PSB充当Lumen pH的传感器，并且通过PSII天线中的ControlSconformationals变化，这是fornPQ激活所需的。在绿色的藻类衣原体中，LHCSR蛋白充当pH传感器并触发NPQ激活。在这里，只有在细胞的HL适应数小时后，才有可能激活NPQ激活，从而启动LHCSR蛋白的合成。 PSB在C. renhardtii中的作用尚不清楚。在过去的资金期间，我们表明，PSB仅在HL暴露的前4-8h期间瞬时表达，并且在HLACCLIMATION约24小时后迅速降解。 PSB定位于类囊体膜，并与PSII相互作用。 PSB的积累与LHCSR积累和NPQ激活并行发生。 PSB的下调导致NPQ容量和LHCSR积累的降低。在没有LHCSR蛋白的情况下，PSB无法补偿LHCSR INNPQ激活的作用，并且PSBS水平升高无法增加NPQCACCAPACTIAS。这表明PSB对于NPQ并不是必不可少的，但对于在适应期间建立高NPQ容量可能是必需的。我们进一步积累了PSB的NPQIntipentedphotativeprotation功能的证据。计划的工作目标是破译C.Reinhardtii中PSB的详细功能。为此，将解决以下中心问题：1）通过CRISPRCAS9和对其NPQ容量和HL AdclimationResponse的表征来产生稳定的PSB敲除线。到目前为止，我们仅分析了PSBS敲门线。 2）确定PSB和OF LHCSR蛋白的相互作用伙伴和化学计量法。 3）PSBS DEGRADATIONPROCESS的表征及其对HL适应的影响。 4）在QE独立的光保护机制中，ThePSBS动力学和HL适应反应的表征。 5）确定PSBS动力学和HL适应于更自然波动（高）光条件的抗气。以前的大多数关于Reinhardtii中HL适应的研究已经与在间歇性的黑暗时期内生长在非天然永久性照明下生长的细胞进行了。包括黑暗时期和波动的光强度的应用使人们有理由期望自然栖息地的令人兴奋的信息，尤其是关于PSB和LHCSR积累的动力学。具有NPQ非依赖性光预脱纤维学缺陷的术语的表征将进一步提供有关PSBS的整合到Reinhardtii的光保护网络中的信息。