Brunk C F, Kahn R W, Sadler L A
Department of Biology, University of California, Los Angeles 90024-1606.
J Mol Evol. 1990 Mar;30(3):290-7. doi: 10.1007/BF02099999.
The species of the Tetrahymena pyriformis complex present a conundrum with regard to their highly conservative morphology and widely divergent molecular characteristics. We have investigated the phylogenetic relationships among these species using the nucleotide sequences from the histone H3II/H4II region of the genome. This region includes portions of the two histone coding sequences, as well as the intergenic region. The DNA sequences of these regions were amplified by the polymerase chain reaction (PCR) and the sequence of each was determined. Nucleotide substitutions and insertions/deletions within this set of sequences were compared to determine the phylogenetic relationships among the species of the complex. These data yield phylogenetic trees with identical topologies when different tree-building routines are used, indicating that the data are very robust. Glaucoma chattoni was used as an outgroup to root the trees for this analysis. The genome organization of G. chattoni and the divergence of its histone H3II/H4II region sequence relative to those of the complex clearly indicate that this species has diverged considerably from the complex. These results show that PCR amplification analysis is feasible over considerable evolutionary distances. However, DNA-DNA hybridization may be more useful than sequence analysis in resolving the relationships among the closely related species in the complex.
梨形四膜虫复合体的物种在其高度保守的形态和广泛不同的分子特征方面存在一个难题。我们使用基因组中组蛋白H3II/H4II区域的核苷酸序列研究了这些物种之间的系统发育关系。该区域包括两个组蛋白编码序列的部分以及基因间区域。这些区域的DNA序列通过聚合酶链反应（PCR）进行扩增，并确定每个序列。比较这组序列中的核苷酸替换和插入/缺失，以确定复合体中各物种之间的系统发育关系。当使用不同的建树程序时，这些数据产生具有相同拓扑结构的系统发育树，表明数据非常可靠。青光眼查顿虫被用作外类群来为该分析的树进行定根。青光眼查顿虫的基因组组织及其组蛋白H3II/H4II区域序列相对于复合体的序列差异清楚地表明，该物种与复合体有很大差异。这些结果表明，PCR扩增分析在相当大的进化距离上是可行的。然而，在解决复合体中密切相关物种之间的关系方面，DNA-DNA杂交可能比序列分析更有用。
