Evolution of cyanelles deduced from constituents of cyenelle envelopes of a glaucocystophyte, Cyanophora paradoxa

从蓝藻藻（Cyanophora paradoxa）的蓝藻包膜成分推论蓝藻的进化

• 批准号: 11640655
• 负责人: KOIKE Hiroyuki
• 金额: $ 1.66万
• 依托单位: Himeji Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11640655/
• 关键词: Glaucocystophyte; cyanelle; envelope; chloroplast; evolution; cyanobacteria

Cyanophora paradoxa posseses a special organelle, a cyanelle, which performs oxygenic photosynthesis. Chloroplasts of eukaryotic photosynthetic organisms are hypothesized to be established by endosymbiosis by a progenitor of cyanobacteria. Investigation of plastid envelope of cyanelles of C.paradoxa will provide some crue to elucidate the evolutionary processes of plastids from endosymbiotic cyanobacteria, sice cyanelles stil preserve some characteristics common to cyanobacteria. In the present research project, we have isolated and characterized envelope membranes from C.paradoxa cyanelles and compared characteristics with those of cyanobacteria and plant chloroplasts.Isolated intact cyanelles were treated with lysozyme and raptured by French Pressure cell treatment. Envelope membranes were purified from the homogenate by sucrose gradient floatation centrifugation. Two yellow fractions were separated. One fraction has a buoyant density of 1.12 g/cm^3 and rich in zeaxanthin. This corresponded to inner envelope membranes. Another fraction with a buoyant density of <1.00 g/cm^3 was rich in β-carotene. This fraction however, did not show membranous structures by observation with electron microscopy. It was concluded that the fraction does not contain envelope membanes.A yellow fraction was found to be remained after detergent treatment of thylakoid membranes. This was rich in zeaxanthin with an estimated buoyant density of 1.18 g/cm^3, and thus estimated to be an outer envelope membranes.The outer envelope membranes have an affinity to that of outer envelope membranes in protein composition, while to that of cyanobacteria in buoyant density and insolubility to detergent. On ther other hand, the protein composition of inner envelope membranes was similar to that of plasma membranes of cyanobactria. The results indicate that the envelope membranes have chimeric nature between cyanobacteria and plants.

蓝绿藻具有一种特殊的细胞器--蓝色素细胞，进行光合作用。真核光合生物的叶绿体被假设是由蓝藻的祖先通过内共生建立的。对奇异金藻（C.paradoxa）胞囊质体被膜的研究将为阐明内共生蓝藻质体的进化过程提供线索，但胞囊仍保留了蓝藻的一些共同特征。在本研究项目中，我们分离和表征了C.paradoxa cyanelles的被膜，并与蓝藻和植物叶绿体的特征进行了比较。通过蔗糖梯度浮选离心从匀浆中纯化包膜。分离出两个黄色级分。其中一部分的浮力密度为1.12 g/cm^3，富含玉米黄质。这对应于内被膜。另一个浮密度<1.00 g/cm^3的组分富含β-胡萝卜素。然而，通过电子显微镜观察，该级分未显示膜结构。结果表明，该组分不含被膜，类囊体膜经去污剂处理后，仍有一个黄色的组分存在。这是一种富含玉米黄质的外被膜，其浮力密度为1.18 g/cm^3，在蛋白质组成上与外被膜相似，而在浮力密度和对去污剂的不溶性上与蓝藻相似。内被膜的蛋白质组成与蓝藻质膜的蛋白质组成相似。结果表明，蓝细菌和植物的被膜具有嵌合性。

项目成果

H.Koike et al.: "Identification of photosystem I components from a Glaucocystophyte, Cyanophora paradoxa, by N-terminal sequencing : the PsaD protein is homologous to that of higher plants"Photosyn.Res.. (in press). (2001)

H.Koike 等人：“通过 N 末端测序鉴定来自蓝藻、Cyanophora paradoxa 的光系统 I 成分：PsaD 蛋白与高等植物的蛋白同源”Photosyn.Res..（出版中）。

H.Koike: "Identification of photosystem I components from a Glaucocystophyte, Cyanophora paradoxa, by N-terminal seguencing"Photosyn.Res.. (印刷中). (2001)

H. Koike：“通过 N 末端测序鉴定来自青囊菌的光系统 I 成分”Photosyn.Res..（出版中）。