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INVESTIGATION ON THE STRUCTURE AND FUNCTION OF PYRENOIDS IN THE CHLOROPLAST OF LOWER PLANTS

低等植物叶绿体中芘类化合物的结构和功能研究

基本信息

批准号：
07304082
负责人：
HORI Terumitsu
金额：
$ 2.62万
依托单位：
UNIVERSITY OF TSUKUBA
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07304082/
关键词：
PYRENOID CHLOROPLAST ALGAE RUBISCO NUCLEOID DNA

项目摘要

Morphological research group : Recent studies indicate that the pyrenoid is an accumulation site of Rubisco in the chloroplast of lower plants. However, Hori demonstrated the localiation of chloroplast DNA in the pyrenoid core of some green algae. We have investigated the behavior of chloroplast DNA and pyrenoids throughout the life cycle of the unicellular green alga, Trebouxia. When the chloroplast divides, the pyrenoid with chloroplast DNA also divides. The chloroplast DNAs are always associated with the pyrenoids during the life cycle of Trebouxia (Miyamura). Ishikawa found the asscoclation of DNAs with lens-shaepd pyrenoids, which are scattered throughout the chloroplast matrix of the diatom, Nitschia sigmoidea. She also found the localization of Rubisco in the pyrenoid core of N.sigmoidea Recently, Suess et al (1995) reported that Rubisco molecules are not highly concentrated in the pyrenoid core of the unicellular green alga, Chlamydomonas reinhardtii. Their results are inconsis … More tent with recent studies in which most of Rubisco molecules are localized in the pyrenoid core. Thus, Nozaki re-examined the distribution of Rubisco in the cells of C.reinhardtii, and found the localization of most of Rubisco molecules in the pyrenoid core using cryo-fixation and immunogold electron microscopy. In Euglena, small subunit of Rubisco is found to be localized in the compartment alized osmiophilic body (COS) in the cytoplasm. This results suggests that the COS is either the cytoplasmic site of chloroplast protein synthesis or an intermediate compartment in the transport of chloroplast proteins from the ER to the chloroplast (Osafune). Hara re-evaluated the ultrastructure of the pyrenoid as the taxonomic character of unicellullar red algae in Porphyridiales using electron microscopy and molecular phylogenetic techniques. This study suggests that Porphyridiales is not a monophyletic group, although the algae belonging to this group is similar in appearance.Physiological research group : Rubisco is the major component of the pyrenoid, and in some algae DNA is also present, as described above. However, it is possible that other minor components are present in the pyrenoid core. Therefore, Okada developed the new biochemical techniques in order to identify the minor components of the pyrenoid. The minor components of the pyrenoid will be identified using this technique in near future. When the extracellular CO_2 concentration is lowered from 5% to ordinary air level in the cells of C.reinhardtii, the pyrenoid has become 1.4-1.6 times larger in volume, and the protein concentration has also increased (Tsuzuki). However, the amount of transcripts of small subunit of Rubisco genes decreases under lower CO_2 concentration. These results suggests that when the pyrenoid develops under lower CO_2 concentration, the Rubisco is accumulated in the pyrenoid instead of the synthesis of new molecules. It is known that the pyrenoid core is traversed by thylakoid membranes in most of algae. Nakayama showed that photosystem II is present in the thylakoid membranes in the pyrenoid. Less

形态学研究小组：近年来的研究表明，类pyrenoid是低等植物叶绿体中Rubisco的积累位点。然而，Hori证明了叶绿体DNA在一些绿藻的类蛋白核中的定位。我们研究了单细胞绿藻Trebouxia的整个生命周期中叶绿体DNA和类pyrenoids的行为。当叶绿体分裂时，含有叶绿体DNA的类核蛋白也分裂。在Trebouxia （Miyamura）的生命周期中，叶绿体dna总是与类pyrenoids相关。石川发现了dna与透镜状核蛋白的关联，这些核蛋白分散在硅藻（Nitschia sigmoidea）的叶绿体基质中。最近，Suess等（1995）报道，Rubisco分子在单细胞绿藻莱茵衣藻（Chlamydomonas reinhardtii）的类pyrenoid核中不高度集中。他们的结果与最近的研究结果不一致，大部分Rubisco分子定位在类pyrenoid核心。因此，Nozaki重新研究了Rubisco在c.r ainhardtii细胞中的分布，并利用冷冻固定和免疫金电镜发现大部分Rubisco分子定位在类pyrenoid核心。在绿藻中，Rubisco的小亚基被发现定位于细胞质中的室化嗜锇小体（COS）。这一结果表明，COS要么是叶绿体蛋白合成的细胞质位点，要么是叶绿体蛋白从内质网转运到叶绿体的中间室（Osafune）。Hara利用电子显微镜和分子系统发育技术对单细胞红藻中的类pyrenoid的超微结构进行了重新评价。这项研究表明，卟啉藻不是一个单系的群体，尽管属于这个群体的藻类在外观上是相似的。生理研究组：Rubisco是类pyrenoid的主要成分，并且在一些藻类DNA中也存在，如上所述。然而，有可能在类pyrenox岩心中存在其他次要成分。因此，冈田开发了新的生化技术，以鉴定类pyrenoid的次要成分。在不久的将来，将利用这种技术鉴定类pyrenox的次要成分。当胞外CO_2浓度从5%降至正常空气水平时，莱茵梭菌细胞内的类pyrenox体积增大1.4 ~ 1.6倍，蛋白质浓度也增加（Tsuzuki）。而低CO_2浓度下，Rubisco小亚基基因的转录量减少。这些结果表明，在较低CO_2浓度条件下，类pyrenoid发育时，Rubisco在类pyrenoid中积累，而不是合成新的分子。众所周知，在大多数藻类中，类囊体膜穿过类核核。Nakayama指出，光系统II存在于类肾小球的类囊体膜中。少