Eukaryotic Components Remodeled Chloroplast Nucleoid Organization during the Green Plant Evolution.
Eukaryotic Components Remodeled Chloroplast Nucleoid Organization during the Green Plant Evolution.
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DOI：
10.1093/gbe/evv233
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发表时间：
2015-11-25
影响因子：
3.3
通讯作者：
Nishimura Y
中科院分区：
文献类型：
--
作者：
Kobayashi Y;Takusagawa M;Harada N;Fukao Y;Yamaoka S;Kohchi T;Hori K;Ohta H;Shikanai T;Nishimura Y
叶绿体(Cp)DNA被认为起源于祖先的内共生体基因组，并被压缩形成核蛋白复合体，cp类核。Cp类核蛋白的结构广泛存在于从单细胞藻类到开花植物的各种植物中，被认为是cpDNA复制、修复/重组、转录和遗传等过程的多功能平台。尽管cp具有基本功能，但开花植物类cp的蛋白质组成被认为与细菌和藻类的蛋白质组成不同，但进化过程仍然难以捉摸。在这项研究中，我们旨在通过分析代表真核光养生物进化的三个阶段的关键生物：绿藻衣藻、轮藻Klebsormidium flaccidum和最基本的陆地植物地钱草，来揭示类CP核组织的进化史。为了阐明莱茵隐翅虫的核心类核蛋白，我们利用高纯度的类核蛋白组分进行了LC-MS/MS分析，并鉴定了一个新的含有SAP结构域的蛋白，该蛋白来源于真核细胞。在此基础上，利用基因组数据库检索了莱茵哈迪氏梭菌、黄花梭菌和多态梭菌中cp类核蛋白的同源基因，并通过细胞生物学/生化分析对其胞内定位和DNA结合活性进行了研究。在这些结果的基础上，我们提出了一个模型，即最初与染色质组织相关的真核因子对类核组织的反复修饰可能是绿色植物进化早期以来类核组织多样化的驱动力。
Chloroplast (cp) DNA is thought to originate from the ancestral endosymbiont genome and is compacted to form nucleoprotein complexes, cp nucleoids. The structure of cp nucleoids is ubiquitously observed in diverse plants from unicellular algae to flowering plants and is believed to be a multifunctional platform for various processes, including cpDNA replication, repair/recombination, transcription, and inheritance. Despite its fundamental functions, the protein composition for cp nucleoids in flowering plants was suggested to be divergent from those of bacteria and algae, but the evolutionary process remains elusive. In this research, we aimed to reveal the evolutionary history of cp nucleoid organization by analyzing the key organisms representing the three evolutionary stages of eukaryotic phototrophs: the chlorophyte alga Chlamydomonas reinhardtii, the charophyte alga Klebsormidium flaccidum, and the most basal land plant Marchantia polymorpha. To clarify the core cp nucleoid proteins in C. reinhardtii, we performed an LC-MS/MS analysis using highly purified cp nucleoid fractions and identified a novel SAP domain-containing protein with a eukaryotic origin as a constitutive core component. Then, homologous genes for cp nucleoid proteins were searched for in C. reinhardtii, K. flaccidum, and M. polymorpha using the genome databases, and their intracellular localizations and DNA binding activities were investigated by cell biological/biochemical analyses. Based on these results, we propose a model that recurrent modification of cp nucleoid organization by eukaryotic factors originally related to chromatin organization might have been the driving force for the diversification of cp nucleoids since the early stage of green plant evolution.