Van der Auwera G, De Wachter R
Department of Biochemistry, University of Antwerp (UIA), Belgium.
J Eukaryot Microbiol. 1998 Sep-Oct;45(5):521-7. doi: 10.1111/j.1550-7408.1998.tb05111.x.
The aim of this study was to compare the usefulness of complete small and large subunit rRNA, and a combination of both molecules, for reconstructing stramenopile evolution. To this end, phylogenies from species of which both sequences are known were constructed with the neighbor-joining, maximum parsimony, and maximum likelihood methods. Also the use of structural features of the rRNAs was evaluated. The large subunit rRNA from the diatom Skeletonema pseudocostatum was sequenced in order to have a more complete taxon sampling, and a group I intron was identified. Our results indicated that heterokont algae are monophyletic, with diatoms diverging first. However, as the analysis was restricted to a particular data set containing merely six taxa, the outcome has limited value for elucidating stramenopile relationships. On the other hand, this approach permits comparison of the performance of both rRNA molecules without interference from other factors, such as a different species selection for each molecule. For the taxa used, the large subunit rRNA clearly contained more phylogenetic information than the small subunit rRNA. Although this result can definitely not be generalized and depends on the phylogeny to be studied, in some cases determining complete large subunit rRNA sequences certainly seems worthwhile.
本研究的目的是比较完整的小亚基和大亚基rRNA以及这两种分子的组合在重建不等鞭毛类进化方面的有用性。为此，使用邻接法、最大简约法和最大似然法构建了已知这两种序列的物种的系统发育树。同时还评估了rRNA结构特征的用途。为了有更完整的分类群样本，对硅藻假微型海链藻的大亚基rRNA进行了测序，并鉴定出一个I类内含子。我们的结果表明，不等鞭毛藻类是单系的，硅藻最先分化出来。然而，由于分析仅限于一个仅包含六个分类群的特定数据集，该结果对于阐明不等鞭毛类关系的价值有限。另一方面，这种方法允许在不受其他因素干扰的情况下比较两种rRNA分子的性能，例如为每个分子选择不同的物种。对于所使用的分类群，大亚基rRNA显然比小亚基rRNA包含更多的系统发育信息。尽管这一结果肯定不能一概而论，且取决于要研究的系统发育，但在某些情况下，确定完整的大亚基rRNA序列似乎确实是值得的。
