Waller Ross F, Keeling Patrick J
Canadian Institute for Advanced Research, Botany Department, University of British Columbia, 3529-6270 University Boulevard, Vancouver, BC, Canada V6T 1Z4.
Gene. 2006 Nov 15;383:33-7. doi: 10.1016/j.gene.2006.07.003. Epub 2006 Jul 20.
The mitochondrial gene for COXII is typically encoded in the organelle genome, however in some members of two unrelated groups, Apicomplexa and Chlorophyceae, cox2 is split into two genes, and both are encoded in the nucleus. Rare genomic changes (RGCs) have acquired popularity as phylogenetic markers, and accordingly this rearrangement of cox2 has been used to infer a possible source of the apicomplexan plastid, the apicoplast, a topic that continues to attract much debate. Accurate interpretation of RGCs, however, is critically dependent on appropriate sampling of the character state of interest amongst relevant taxa. Dinoflagellates form the sister taxon to Apicomplexa, and therefore the state of their cox2 is essential to the interpretation of this apparent RGC. Here we present the first complete cox2 data from dinoflagellates, that suggests despite the remarkable similarity of cox2 seen in Alveolates and Chlorophyceae, this gene reorganization arose independently in these two groups, not through lateral transfer as previously suggested.
细胞色素氧化酶亚基II（COXII）的线粒体基因通常编码于细胞器基因组中，然而在两个不相关类群（顶复门和绿藻纲）的一些成员中，cox2被分割成两个基因，且二者均编码于细胞核中。罕见基因组变化（RGCs）作为系统发育标记已受到广泛关注，因此cox2的这种重排已被用于推断顶复门生物质体（顶质体）的可能来源，这一话题仍备受争议。然而，对RGCs的准确解读严重依赖于在相关分类群中对感兴趣的性状状态进行适当抽样。甲藻是顶复门的姐妹分类群，因此其cox2的状态对于解读这一明显的RGC至关重要。在此，我们展示了来自甲藻的首个完整的cox2数据，这表明尽管在囊泡虫类和绿藻纲中cox2有显著相似性，但该基因重排在这两个类群中是独立发生的，并非如先前所认为的通过横向转移产生。
