Mitochondrial genome organization, expression and evolution in the dinoflagellate Crypthecodinium cohnii.
Mitochondrial genome organization, expression and evolution in the dinoflagellate Crypthecodinium cohnii.
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甲藻 Crypthecodinium cohnii 中的线粒体基因组组织、表达和进化。
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发表时间：
2001
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通讯作者：
J. E. Norman
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作者：
J. E. Norman
为了更好地理解线粒体基因组是如何进化的，我研究了非光合鞭毛藻隐藻（Crypthecodinium cohnii）线粒体基因的结构、组织、表达和进化关系。在鞭毛动物的两个最近的亲戚中，顶复合体（一组细胞内寄生虫）和纤毛虫，线粒体DNA （mtDNA）已经被表征。因此，本文要解决的具体问题是：cohnii的线粒体基因组与顶复合体还是纤毛虫更相似？为了回答这个问题，我们从cox1和cob基因的mtDNA中测定了cox1和cob基因的DNA序列以及侧翼序列。cox1基因在cohnii的mtDNA中存在于四个不同但相关的背景中，其中心重复单元被两个可能的上游（侧翼结构域1或2）和下游（侧翼结构域3或4）区域之一所包围。cox1编码序列的大部分位于中心重复序列内，然而，开放阅读框的c端部分延伸到两侧的结构域3和4，从而形成两个不同的cox1 orf。序列分析表明，其中一个cox1 orf的c端可以折叠成高度稳定的RNA结构，可能使其形成稳定的mRNA。在cob中也可以看到类似的模式，除了含有cob的元素表现出五个不同的c端侧翼区域，产生三个不同的orf。cohnii线粒体基因的排列似乎是不同含基因序列上下文在中心重复序列内同源重组的结果。这种重组重复是植物（被子植物）mtDNA的一个特征，但它们以前没有在原生生物的线粒体基因组中被描述过。
To better understand how mitochondrial genomes evolve, I investigated the structure, organization, expression and evolutionary affiliations of mitochondrial genes in the non-photosynthetic dinoflagellate Crypthecodinium cohnii. In each of the two closest relatives of the dinoflagellates, apicomplexans (a group of intracellular parasites) and ciliates, mitochondrial DNA (mtDNA) has been characterized. Therefore, the specific question that this thesis addresses is: Is the mitochondrial genome of C. cohnii more similar to that of the apicomplexans or the ciliates? To answer this question, the DNA sequences of cox1 and cob genes as well as flanking sequences were determined from C. cohnii mtDNA. The cox1 gene exists in four distinct but related contexts in C. cohnii mtDNA, with a central repeat unit flanked by one of two possible upstream (flanking domain 1 or 2) and downstream (flanking domain 3 or 4) regions. The majority of the cox1 coding sequence is located within the central repeat: however, the C-terminal portion of the open reading frame extends into flanking domains 3 and 4, thereby creating two distinct cox1 ORFs. Sequence analysis showed that the C-terminal end of one of the cox1 ORFs can fold into a highly stable RNA structure, presumably allowing it to form a stable mRNA. A similar pattern is seen with cob, with the exception that cob-containing elements exhibit five different C-terminal flanking regions, generating three distinct ORFs. The arrangement of mitochondrial genes in C. cohnii appears to be the result of homologous recombination within the central repeat between different gene-containing sequence contexts. Such recombining repeats are a characteristic feature of plant (angiosperm) mtDNA, but they have not previously been described in the mitochondrial genomes of protists.