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

为了分析精子包在殖民科Volvocaceae和Goniaceae中进化的系统发育位置，基于形态学资料的分支分析推断了这两个科之间的系统发育关系。该分析的严格共识树表明，精子包在类似山石藻的异母藻中进化产生了一个单系群，包括异母/卵母藻属的尤多里纳属、Platydorina属、Pleodorina属和Volvox属。此外，基于rbcL基因序列数据的系统发育分析表明，具有较高的自引导值，存在一个由几乎所有异配型/异配型线虫组成的单系类群，其中秀丽线虫是最原始的物种。因此，这表明与秀丽隐杆线虫精子包相关的基因在异体/卵异体群体中是最原始的。因此，比较真丝藻的这些基因与山石氏菌的同源基因，可能有助于研究与精子包有关的基因的进化。作为从Yamagishiella-like藻类中研究与精子包相关的eudolina基因进化的第一步，基于差异筛选方法分离秀丽隐杆线虫中与精子包相关的基因似乎是必不可少的。因此，建立了在秀丽隐杆线虫培养物中大量诱导精子包的方法。大约20%的培养细胞被诱导发育成精子包，使用培养箱（25 C）和含有Pleodorina交配培养基的大烧瓶（Nozaki et al., phyologia 28: 252-267,1989）连续充气。比较分析从诱导精子包和营养细胞中提取的mRNA将解决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.