A LHCB9-dependent photosystem I megacomplex induced under low light in Physcomitrella patens
A LHCB9-dependent photosystem I megacomplex induced under low light in Physcomitrella patens
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DOI：
10.1038/s41477-018-0270-2
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发表时间：
2018-11-01
期刊：
影响因子：
18
通讯作者：
Bassi, Roberto
中科院分区：
文献类型：
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作者：
Pinnola, Alberta;Alboresi, Alessandro;Bassi, Roberto
苔藓小立碗藓 (Physcomitrella patens) 的光系统 I 具有特殊的性质，包括进行非光化学荧光猝灭的能力。我们研究了野生型苔藓和具有 Ihcb9（光捕获复合体）敲除基因型的苔藓中光系统 I 在不同光照和碳供应条件下的组织，该基因型缺乏具有红移吸收形式的天线蛋白。当野生型苔藓在糖和弱光下生长时，会积累 LHCB9 蛋白和大量的光系统 I 超复合物，其中除了典型的四个 LHCI 亚基外，还包括一个 LHCII 三聚体和四个额外的 LHC 单体。无论生长条件如何，Ihcb9 敲除都会产生具有四个 LHCI 亚基的类被子植物光系统 I 超复合物。在亚致死浓度的电子传递抑制剂存在下的生长会导致质体醌库的氧化或还原，从而分别阻止或促进LHCB9的积累和光系统I巨型复合物的形成。我们认为，LHCB9 是调节光系统 I 触角大小以及避免质体醌过度还原的能力的关键亚基：这种情况在苔藓典型的遮荫和富含阳光斑点的环境中具有潜在危险，其质体醌池因光系统 II 和糖底物的氧化而减少。
Photosystem I of the moss Physcomitrella patens has special properties, including the capacity to undergo non-photochemical fluorescence quenching. We studied the organization of photosystem I under different light and carbon supply conditions in wild-type moss and in moss with the Ihcb9 (light-harvesting complex) knockout genotype, which lacks an antenna protein endowed with red-shifted absorption forms. Wild-type moss, when grown on sugars and in low light, accumulated LHCB9 proteins and a large form of the photosystem I supercomplex, which, besides the canonical four LHCI subunits, included a LHCII trimer and four additional LHC monomers. The Ihcb9 knockout produced an angiosperm-like photosystem I supercomplex with four LHCI subunits irrespective of the growth conditions. Growth in the presence of sublethal concentrations of electron transport inhibitors that caused oxidation or reduction of the plastoquinone pool prevented or promoted, respectively, the accumulation of LHCB9 and the formation of the photosystem I megacomplex. We suggest that LHCB9 is a key subunit regulating the antenna size of photosystem I and the ability to avoid the over-reduction of plastoquinone: this condition is potentially dangerous in the shaded and sunfleck-rich environment typical of mosses, whose plastoquinone pool is reduced by both photosystem II and the oxidation of sugar substrates.