The remarkable chloroplast genome of dinoflagellates
The remarkable chloroplast genome of dinoflagellates
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DOI：
10.1093/jxb/erm292
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发表时间：
2008-03-01
影响因子：
6.9
通讯作者：
Barbrook, Adrian C.
中科院分区：
文献类型：
--
作者：
Howe, Christopher J.;Nisbet, R. Ellen R.;Barbrook, Adrian C.
甲藻是经济和生态上重要的真核藻类。它们的叶绿体基因组的组织似乎与植物和其他藻类的叶绿体基因组的组织截然不同。随着基因大规模转移到细胞核，甲藻中的基因含量急剧减少。其余的大部分基因编码光系统 I 和 II 的亚基、细胞色素 b(6)f 复合物和 ATP 合酶，以及 rRNA 和一些 tRNA。传统叶绿体基因组的所有基因都物理连接在一个分子上，而甲藻叶绿体基因则位于小质粒上，称为“小环”。每个小环至多有几个基因和一个可区分的“核心”区域。基因相对于核心区域始终处于相同的方向。还存在非编码小环，包括明显通过重排从其他小环衍生而来的异常形式的小环。讨论了小环位于叶绿体中以及除了小环之外不存在常规叶绿体基因组的证据。小环的转录可能在接近核心的地方开始，产生对应于几乎整个小环的转录本。然后转录物被切割成与单个基因相对应的分子。转录后修饰包括编辑和添加 PolyU 尾。讨论了为什么这些特殊基因保留在甲藻叶绿体中，以及叶绿体向线粒体提供 fMet-tRNA 的可能性。
Dinoflagellates are an economically and ecologically important eukaryotic algal group. The organization of their chloroplast genome appears to be radically different from that in plants and other algae. The gene content has been dramatically reduced in dinoflagellates, with the large-scale transfer of genes to the nucleus. Most of the remaining genes encode subunits of Photosystems I and II, the cytochrome b(6)f complex, and ATP synthase, as well as rRNAs and a few tRNAs. Whereas conventional chloroplast genomes have all their genes physically linked on one molecule, dinoflagellate chloroplast genes are located on small plasmids, termed 'minicircles'. Each minicircle has at most a few genes, and a distinguishable 'core' region. Genes are always in the same orientation with respect to the core region. There are also non-coding minicircles, including aberrant forms of minicircles apparently derived from other minicircles by rearrangement. The evidence that the minicircles are located in the chloroplast and that there is no conventional chloroplast genome in addition to the minicircles is discussed. Transcription of minicircles is probably initiated close to the core, generating transcripts corresponding to an almost entire minicircle. The transcripts are then cleaved to molecules corresponding to individual genes. Post-transcriptional modifications include editing and addition of a polyU tail. It is discussed why these particular genes have been retained in the dinoflagellate chloroplast, together with the possibility that the chloroplast supplies fMet-tRNA to the mitochondrion.