Department of Systematic Botany, Evolutionary Biology Centre, Norbyvägen 18D, University of Uppsala, SE-75420 Uppsala, Sweden.
Protist. 2010 Oct;161(4):539-48. doi: 10.1016/j.protis.2009.12.006. Epub 2010 Mar 19.
The dictyostelids possess a complex life cycle including aggregative and multicellular stages. They also include one of the most widely studied protistan model organisms, Dictyostelium discoideum. The current molecular phylogeny of dictyostelids is based largely on SSU (18S) rDNA sequences and shows a deep taxon consisting of four major groups, none of which correspond to the three traditional morphologically-defined genera. However, due to the generally slowly evolving nature of SSU rDNA, these data fail to resolve the majority of branches within the four groups. Given the highly morphologically mixed nature of the dictyostelid groups, it is important to resolve relationships within them. We have determined sequences for the internal transcribed spacers (ITS) of rDNA for nearly all species in the original dictyostelid global phylogeny. Phylogenetic analyses of these data, in combination with the previously determined SSU rDNA sequences, confidently resolve nearly all branches in the tree. This now fully resolved phylogeny confirms the utility of ITS for dictyostelid systematics and lays the ground work for further evolutionary study of the group.
盘基网柄菌目生物具有复杂的生命周期，包括聚集和多细胞阶段。其中还包括研究最多的原生动物模式生物之一——盘基网柄菌。目前，盘基网柄菌目的分子系统发育主要基于 SSU（18S）rDNA 序列，显示出一个由四个主要类群组成的深系群，没有一个类群与传统的形态定义的三个属相对应。然而，由于 SSU rDNA 通常进化缓慢，这些数据无法解决四个类群内的大多数分支。鉴于盘基网柄菌类群的高度形态混合性质，解决它们内部的关系非常重要。我们已经确定了原始盘基网柄菌全球系统发育中几乎所有物种的 rDNA 内转录间隔区（ITS）序列。对这些数据的系统发育分析，结合以前确定的 SSU rDNA 序列，自信地解决了树中的几乎所有分支。这个完全解决的系统发育图证实了 ITS 在盘基网柄菌类群系统学中的有用性，并为该群体的进一步进化研究奠定了基础。
