Molecular phylogenetic study on genes related to sperm packets in the Volvocaceae (Chlorophyta)

为了分析团藻科（Volvocaceae）和戈尼亚科（Goniaceae）精子包的进化系统位置，基于形态学数据的分支系统学分析，推断了这两个科内部的系统发育关系。严格的共识树的分析表明，精子包在Yamagishiella等的同花受精卵进化产生一个单系群，包括异花受精/卵受精属Eudorina，Platydorina，Pleodorina和团藻。此外，系统发育分析的基础上的rbcL基因序列数据表明，具有较高的自举值，存在一个单系群组成的几乎所有成员的异配/卵配volvocacean物种，其中Eudorina elegans被解决为最原始的物种。因此，这表明，与精子包的秀丽隐杆线虫的基因是最原始的异配/卵配集团。因此，比较Eudorina与Yamagishiella同源基因的差异，研究精子包相关基因的进化可能是有益的。作为研究Eudorina精子包相关基因从Yamagishiella类线虫基因进化的第一步，基于差异筛选方法分离E.elegans精子包相关基因显得至关重要。因此，建立了在大体积的秀丽隐杆线虫培养物中诱导精子包的方法。通过使用培养箱（25 ℃）和含有Pleodorina交配培养基的大烧瓶（Nozaki等人，Phycologia 28：252- 267，1989）连续充气。比较分析诱导后的精子包和营养细胞中的mRNA，可以揭示精子包相关基因的系统发育特征。

In order to analyze the phylogenetic position of evolution of sperm packets in the colonial families Volvocaceae and Goniaceae, phylogenetic relationships within these families were inferred based on the cladistic analysis of the morphological data. The strict consensus tree of this analysis indicated that sperm packets evolved in a Yamagishiella-like isogamous alga to give rise to a monophyletic group comprising the anisogamous/oogamous genera Eudorina, Platydorina, Pleodorina and Volvox. Furthermore, phylogenetic analysis based on the rbcL gene sequence data suggested, with high bootstrap values, the presence of a monophyletic group composed of almost all the members of the anisogamous/oogamous volvocacean species, in which Eudorina elegans was resolved as the most primitive species. It is, therefore, suggested that the genes related to the sperm packets of E.elegans is most primitive within the anisogamous/oogamous group. Thus is may be fruitful to compare such genes of Eudorina and homologous genes of Yamagishiella in order to study the evolution of genes related to sperm packets.As the first step to study the evolution of Eudorina genes related to sperm packets from genes in a Yamagishiella-like alga, isolation of genes related to sperm packets in E.elegans based on differential screening methods seemed to be essential. Therefore, methods to induce sperm packets in a large volume of E.elegans culture were established. Approximately 20% of cultured cells were induced to develop into sperm packets by using an incubator (25ﾟC) and a large flask containing Pleodorina mating medium (Nozaki et al., Phycologia 28 : 252-267,1989) continuously aerated. Comparative analyzes of mRNA extracted from the induced sperm packets and vegetative cells will resolve the phylogenetic characteristics of the genes related to sperm packets.