Life history and molecular phylogenetic relationships of Asterocladon interjectum sp. nov. (Phaeophyceae)
Life history and molecular phylogenetic relationships of Asterocladon interjectum sp. nov. (Phaeophyceae)
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DOI：
10.1080/09670260500128285
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发表时间：
2005-05
影响因子：
2.4
通讯作者：
S. Uwai;Chikako Nagasato;T. Motomura;K. Kogame
中科院分区：
文献类型：
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作者：
S. Uwai;Chikako Nagasato;T. Motomura;K. Kogame
从日本太平洋沿岸分离到一种小型的匍匐丝状褐天牛，对其生活史、形态、超微结构和分子系统学进行了研究。该分离物具有同形、双相的生活史和异配生殖。配子发生受温度调节，仅在≤14°C的温度下发生。在较高的温度下，配子体通过无性生殖的方式繁殖。多室和单室zoidangia的所有swarmer缺乏眼点。孢子体和配子体都有寡柄丝状轴，侧毛具基鞘，没有直立的叶状体。三到八个长圆形的叶绿体，每个都有一个突出的蛋白核，聚集形成一个星状的叶绿体构型。所有这些形态特征都表明该种植物属于星枝藻属。然而，多室配子囊产生于中间或末端位置，而带状虫缺乏眼斑，这与以前唯一的属Asterocladon lobatum不同。基于RUBISCO大亚基（rbcL）和SSU核核糖体RNA基因部分序列的分子系统发育分析表明，Asterocladon interjectum sp. nov. interjectum，A. lobatum和Asteronema rhodochortonoides一起形成了一个单系分支，姐妹的Ectocarpales广义。由于分子系统发育分析表明星丝藻属是并系的，而星枝藻属是单系的。和Asteronema rhodochortonoides的支持下，缺乏细胞质内陷的蛋白核，Asteronema rhodochortonoides转移到Asterocladon和一个修订的属界定Asterocladon。
A small prostrate filamentous brown alga, isolated from the warm temperate Pacific coast of Japan, was cultured to investigate its life history, morphology, ultrastructure and molecular phylogenetic position. The isolate had an isomorphic, diphasic life history with anisogamous sexual reproduction. Gametogenesis was regulated by temperature and occurred only at temperatures ≤14°C. At higher temperatures, gametophytes reproduced by means of asexual zoids. All swarmers from plurilocular and unilocular zoidangia lacked an eyespot. Both sporophytes and gametophytes had oligostichous filamentous axes, lateral hairs with a basal sheath and no erect thalli. Three to eight oblong chloroplasts, each with a protruding pyrenoid, aggregated to form a stellate chloroplast configuration. All these morphological features suggested that this alga belongs to the genus Asterocladon. Plurilocular gametangia produced in an intercalary or terminal position and zoids lacking eyespots, are, however, unlike those of Asterocladon lobatum, formerly the only member of the genus. Therefore, we described the alga as a new taxon, Asterocladon interjectum sp. nov. Molecular phylogenetic analyses based on the large RUBISCO subunit (rbcL) and partial SSU nuclear ribosomal RNA gene sequences showed that A. interjectum, A. lobatum and Asteronema rhodochortonoides together formed a monophyletic clade, sister to the Ectocarpales sensu lato. Because the molecular phylogenetic analyses showed Asteronema to be paraphyletic, but monophyly of Asterocladon spp. and Asteronema rhodochortonoides was supported by the absence of cytoplasmic invaginations in pyrenoids, Asteronema rhodochortonoides was transferred to Asterocladon and an emended generic circumscription of Asterocladon was included.