Hatena arenicola gen. et sp nov., a katablepharid undergoing probable plastid acquisition
Hatena arenicola gen. et sp nov., a katablepharid undergoing probable plastid acquisition
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DOI：
10.1016/j.protis.2006.05.011
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发表时间：
2006-10-01
期刊：
影响因子：
2.5
通讯作者：
Inouye, Isao
中科院分区：
文献类型：
--
作者：
Okamoto, Noriko;Inouye, Isao
沙生哈藤属，描述了一种神秘的鞭毛虫。它显示超微结构的亲和力katablepharids，包括大和小的喷射体，细胞覆盖，和一个喂养装置。虽然18S核糖体DNA的分子遗传学支持其分类为katablepharids，细胞的特征是背腹压缩的细胞形状和爬行运动，这两个都是不寻常的在这个组。Hatena arenicola最显著的特征是它拥有一个共生体。这种共生与先前报道的持续共生的情况不同，因为共生体质体被选择性地扩大，而其他结构如线粒体、高尔基体、细胞骨架和内膜系统被降解;宿主和共生体已经发展出一种形态学关联，即，共生体的眼点始终位于沙生哈藤的细胞顶端，在细胞分裂过程中只有一个子细胞继承共生体，导致一个共生体的绿色细胞和一个无共生体的无色细胞。有趣的是，无色细胞有一个进食器官，对应于共生体承载细胞中的眼点位置，它们能够以猎物细胞为食。这表明宿主的形态取决于共生体的存在或不存在。这些观察结果表明，Hatena arenicola有一个独特的“半植物，半捕食者”的生活周期;一个细胞分裂成一个自养细胞拥有一个共生的Nephroselmis物种，和一个共生缺乏无色细胞，后来发展出一个新的喂养装置。Hatena arenicola作为质体收购的中间步骤的进化意义进行了讨论的背景下，正在进行的内共生的甲藻的其他例子。(c)2006年Elsevier GmbH。All rights reserved.
Hatena arenicola gen. et sp. nov., an enigmatic flagellate of the katablepharids, is described. It shows ultrastructural affinities to the katablepharids, including large and small ejectisomes, cell covering, and a feeding apparatus. Although molecular phylogenies of the 18S ribosomal DNA support its classification into the katablepharids, the cell is characterized by a dorsiventrally compressed cell shape and a crawling motion, both of which are unusual within this group. The most distinctive feature of Hatena arenicola is that it harbors a Nephroselmis symbiont. This symbiosis is distinct from previously reported cases of ongoing symbiosis in that the symbiont plastid is selectively enlarged, while other structures such as the mitochondria, Golgi body, cytoskeleton, and endomembrane system are degraded; the host and symbiont have developed a morphological association, i.e., the eyespot of the symbiont is always at the cell apex of Hatena arenicola; and only one daughter cell inherits the symbiont during cell division, resulting in a symbiont-bearing green cell and a symbiont-lacking colorless cell. Interestingly, the colorless cells have a feeding apparatus that corresponds to the location of the eyespot in symbiont-bearing cells, and they are able to feed on prey cells. This indicates that the morphology of the host depends on the presence or absence of the symbiont. These observations suggest that Hatena arenicola has a unique "half-plant, half-predator" life cycle; one cell divides into an autotrophic cell possessing a symbiotic Nephroselmis species, and a symbiont-lacking colorless cell, which later develops a feeding apparatus de novo. The evolutionary implications of Hatena arenicola as an intermediate step in plastid acquisition are discussed in the context of other examples of ongoing endosymbioses in dinoflagellates. (c) 2006 Elsevier GmbH. All rights reserved.