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Molecular genetic study on gene expression in chloroplasts.

叶绿体基因表达的分子遗传学研究。

基本信息

批准号：
62480001
负责人：
OZEKI Haruo
金额：
$ 4.22万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1988
项目状态：
已结题

项目摘要

Chloroplast genes are expressed within the prganelles via their own machinery for prttein biogenesis, although the machinery itself is composed not only of their own gene products but also of the nuclear gene products. We have determined the entire DNA sequence of liverwort chloroplast genome and deduced 127 distinct genes. About half of them are concerned with the basic mechanisms of gene expression in the chloroplasts, such as transcription and translation, and share many features with prokaryotic organisms. Chloroplast ribosomes are prokaryotic 70S, and genetic signals such as promotors, terminatews, SD-sequences etc. are also bacteria types. Thus the genetic system of chloroplasts is basically prokaryotic, supporting the hypothesis of endosymbiotic origin of bacteria. On the other hand, however, many chloroplast genes are interruped by introns(catalytic ones of hroup I or II), differring from bacteria, and thus require post-transcriptional RNA splicing for their gene expression. Analysis of chloroplast RNAs prepared from cultured liverwort cells showed that the primary RNA transcripts usually contained poly-cistronic messages which were then processed into smaller mRNAs prior to splicing. If a gene contained two introns, the splicing proceeded successively from the 5' to 3' direction. We also proposed a bimolecular interaction model for trans-splicing. In conclusion, we postulated matulation pathways for mRNAs in chloroplasts from the primary RNA transcripts via RNA processing and splicing cis and trans.

叶绿体基因通过它们自己的生物合成机制在原核内表达，尽管这种机制本身不仅由它们自己的基因产物组成，而且也由核基因产物组成。我们测定了苔类植物叶绿体基因组的全序列，推导出127个差异基因。其中约一半涉及叶绿体中基因表达的基本机制，如转录和翻译，并与原核生物有许多共同特征。叶绿体核糖体是原核生物的70S，启动子、终止子、SD序列等遗传信号也是细菌的类型。因此，叶绿体的遗传系统基本上是原核的，支持细菌内共生起源的假说。然而，另一方面，许多叶绿体基因被内含子（hroupI或II的催化内含子）中断，这与细菌不同，因此需要转录后RNA剪接来表达它们的基因。从培养的苔类植物细胞中制备的叶绿体RNA的分析表明，初级RNA转录物通常含有多顺反子信息，然后在剪接之前加工成较小的mRNA。如果一个基因含有两个内含子，剪接从5'到3'方向连续进行。我们还提出了一个反式剪接的双分子相互作用模型。总之，我们假设叶绿体中的mRNA通过RNA加工和顺式和反式剪接从初级RNA转录物中产生的matulation途径。