Humboldt-Universität zu Berlin, Lebenswissenschaftliche Fakultät, Institut für Biologie, AG Pflanzenphysiologie, 10115 Berlin, Germany.
Humboldt-Universität zu Berlin, Lebenswissenschaftliche Fakultät, Institut für Biologie, AG Pflanzenphysiologie, 10115 Berlin, Germany
Plant Physiol. 2018 Aug;177(4):1453-1472. doi: 10.1104/pp.18.00540. Epub 2018 Jun 21.
The members of the light-harvesting complex protein family, which include the one-helix proteins (OHPs), are characterized by one to four membrane-spanning helices. These proteins function in light absorption and energy dissipation, sensing light intensity, and triggering photomorphogenesis or the binding of chlorophyll and intermediates of chlorophyll biosynthesis. Arabidopsis () contains two OHPs, while four homologs (named high-light-induced proteins) exist in PCC6803. Various functions have been assigned to high-light-induced proteins, ranging from photoprotection and the assembly of photosystem I (PSI) and PSII to regulation of the early steps of chlorophyll biosynthesis, but little is known about the function of the two plant OHPs. Here, we show that the two Arabidopsis OHPs form heterodimers and that the stromal part of OHP2 interacts with the plastid-localized PSII assembly factor HIGH CHLOROPHYLL FLUORESCENCE244 (HCF244). Moreover, concurrent accumulation of the two OHPs and HCF244 is critical for the stability of all three proteins. In particular, the absence of OHP2 leads to the complete loss of OHP1 and HCF244. We used a virus-induced gene silencing approach to minimize the expression of or in adult Arabidopsis plants and revealed that OHP2 is essential for the accumulation of the PSII core subunits, while the other photosynthetic complexes and the major light-harvesting complex proteins remained unaffected. We examined the potential functions of the OHP1-OHP2-HCF244 complex in the assembly and/or repair of PSII and propose a role for this heterotrimeric complex in thylakoid membrane biogenesis.
光捕获复合物蛋白家族成员的特征是具有一到四个跨膜螺旋，包括单螺旋蛋白 (OHPs)。这些蛋白在光吸收和能量耗散、感知光强以及触发光形态发生或叶绿素和叶绿素生物合成中间产物的结合中发挥作用。拟南芥含有两个 OHPs，而 PCC6803 中存在四个同源物（称为高光诱导蛋白）。高光诱导蛋白具有各种功能，从光保护和 PSI 和 PSII 的组装到调节叶绿素生物合成的早期步骤，但对两种植物 OHPs 的功能知之甚少。在这里，我们表明两种拟南芥 OHPs 形成异源二聚体，并且 OHP2 的基质部分与质体定位的 PSII 组装因子 HIGH CHLOROPHYLL FLUORESCENCE244 (HCF244) 相互作用。此外，两种 OHPs 和 HCF244 的同时积累对于这三种蛋白质的稳定性至关重要。特别是，没有 OHP2 会导致 OHP1 和 HCF244 的完全丢失。我们使用病毒诱导的基因沉默方法最大限度地减少成年拟南芥植物中 或 的表达，并揭示 OHP2 对于 PSII 核心亚基的积累是必不可少的，而其他光合复合物和主要的光捕获复合物蛋白保持不变。我们研究了 OHP1-OHP2-HCF244 复合物在 PSII 组装和/或修复中的潜在功能，并提出该异源三聚体复合物在类囊体膜生物发生中的作用。
