Budding of the Alveolate Alga Vitrella brassicaformis Resembles Sexual and Asexual Processes in Apicomplexan Parasites
Budding of the Alveolate Alga Vitrella brassicaformis Resembles Sexual and Asexual Processes in Apicomplexan Parasites
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DOI：
10.1016/j.protis.2016.12.001
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发表时间：
2017-02-01
期刊：
影响因子：
2.5
通讯作者：
Obornik, Miroslav
中科院分区：
文献类型：
--
作者：
Fussy, Zoltan;Masarova, Petra;Obornik, Miroslav
易于培养和基因组数据的可用性促进了对顶复合体的自由生活光养亲缘关系的深入研究，即铬虫（Chromera velia）和Vitrella brassicaformis。Chromera和Vitrella在生理、形态、系统发育位置和基因组特征上存在显著差异，但Vitrella并没有得到足够的关注。这里我们描述两种类型的动物孢子虫。一种包含游动孢子，被大致结构的物质包围，胞浆内轴索预计在孢子释放后发育成成熟的鞭毛，类似于疟原虫的小配子；在第二种类型中，细胞同时从孢子囊中心萌发，被光滑物质包围，鞭毛在细胞外发育。这个出芽的过程与弓形虫的小孢子形成过程类似。我们认为这些过程中的一个（或两个）产生配子样鞭毛虫后代。基于活体染色，游动孢子融合确实发生在芸苔状芽孢杆菌的培养。我们没有在任何生命阶段发现类似假锥体的根尖结构。因此，V brassicaformis可能代表缺乏根尖复合体的祖先状态，或者是次生地失去了根尖复合体。我们认为，顶复合体和“色素体”的共同祖先表现出一个复杂的生命周期，在色素体和色素体中，这一生命周期因其所处的环境而减少。(C)2016 Elsevier GmbH版权所有。
Ease of cultivation and availability of genomic data promoted intensive research of free-living phototrophic relatives of apicomplexans, i.e. Chromera velia and Vitrella brassicaformis. Chromera and Vitrella differ significantly in their physiology, morphology, phylogenetic position and genomic features, but Vitrella has not gained as much attention. Here we describe two types of Vitrella zoosporangia. One contains zoospores surrounded by roughly structured matter, with an intracytoplasmic axoneme predicted to develop into a mature flagellum upon spore release, similarly to Plasmodium microgametes; in the second type, cells concurrently bud off the center of the sporangium, surrounded by smooth matter, and flagella develop extracellularly. This process of budding is reminiscent of microsporogenesis as seen in Toxoplasma. We suggest one (or both) of these processes generates gamete-like flagellate progeny. Based on live staining, fusion of zoospores does occur in cultures of V. brassicaformis. We failed to find an apical structure similar to the pseudoconoid in any life stage. V brassicaformis may therefore either represent an ancestral state lacking an apical complex or has lost the apical complex secondarily. We propose that the common ancestor of Apicomplexa and "chrompodellids" exhibited a complex life cycle, which was reduced in chromerids and colpodellids as dictated by their environment. (C)2016 Elsevier GmbH. All rights reserved.