Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, P.R. China; University of the Chinese Academy of Sciences, Beijing 100049, P.R. China.
Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, P.R. China; China National Botanical Garden, Beijing 100093, P.R. China; Academician Workstation of the Agricultural High-Tech Industrial Area of the Yellow River Delta, National Center of Technology Innovation for Comprehensive Utilization of Saline-Alkali Land, Dongying 257300, P.R. China.
Plant Commun. 2024 Nov 11;5(11):101041. doi: 10.1016/j.xplc.2024.101041. Epub 2024 Jul 18.
Diatoms, a group of prevalent marine algae, contribute significantly to global primary productivity. Their substantial biomass is linked to enhanced absorption of blue-green light underwater, facilitated by fucoxanthin chlorophyll (Chl) a/c-binding proteins (FCPs), which exhibit oligomeric diversity across diatom species. Using mild clear native PAGE analysis of solubilized thylakoid membranes, we displayed monomeric, dimeric, trimeric, tetrameric, and pentameric FCPs in diatoms. Mass spectrometry analysis revealed that each oligomeric FCP has a specific protein composition, and together they constitute a large Lhcf family of FCP antennas. In addition, we resolved the structures of the Thalassiosira pseudonana FCP (Tp-FCP) homotrimer and the Chaetoceros gracilis FCP (Cg-FCP) pentamer by cryoelectron microscopy at 2.73-Å and 2.65-Å resolution, respectively. The distinct pigment compositions and organizations of various oligomeric FCPs affect their blue-green light-harvesting, excitation energy transfer pathways. Compared with dimeric and trimeric FCPs, the Cg-FCP tetramer and Cg-FCP pentamer exhibit stronger absorption by Chl c, redshifted and broader Chl a fluorescence emission, and more robust circular dichroism signals originating from Chl a-carotenoid dimers. These spectroscopic characteristics indicate that Chl a molecules in the Cg-FCP tetramer and Cg-FCP pentamer are more heterogeneous than in both dimers and the Tp-FCP trimer. The structural and spectroscopic insights provided by this study contribute to a better understanding of the mechanisms that empower diatoms to adapt to fluctuating light environments.
硅藻，一种普遍存在的海洋藻类，对全球初级生产力有重要贡献。它们大量的生物量与水下对蓝绿光的增强吸收有关，这得益于叶黄素叶绿素 a/c 结合蛋白（FCPs），这些蛋白在硅藻物种中表现出寡聚多样性。通过对溶解的类囊体膜进行温和的清晰天然 PAGE 分析，我们在硅藻中展示了单体、二聚体、三聚体、四聚体和五聚体 FCP。质谱分析表明，每种寡聚 FCP 都有特定的蛋白质组成，它们共同构成了一个大型 Lhcf 家族的 FCP 天线。此外，我们通过低温电子显微镜解析了 Thalassiosira pseudonana FCP（Tp-FCP）三聚体和 Chaetoceros gracilis FCP（Cg-FCP）五聚体的结构，分辨率分别为 2.73-Å 和 2.65-Å。不同寡聚 FCP 的不同色素组成和组织影响了它们对蓝绿光的吸收、激发能量转移途径。与二聚体和三聚体 FCP 相比，Cg-FCP 四聚体和 Cg-FCP 五聚体对 Chl c 的吸收更强，Chl a 荧光发射红移且更宽，以及源自 Chl a-类胡萝卜素二聚体的更稳健的圆二色性信号。这些光谱特征表明，Cg-FCP 四聚体和 Cg-FCP 五聚体中的 Chl a 分子比二聚体和 Tp-FCP 三聚体中的更不均匀。本研究提供的结构和光谱见解有助于更好地理解使硅藻适应波动的光照环境的机制。
