Genetic characterization and life cycle of the diatom Fragilariopsis kerguelensis
Genetic characterization and life cycle of the diatom Fragilariopsis kerguelensis
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DOI：
10.1080/09670262.2013.849360
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发表时间：
2013-11-01
影响因子：
2.4
通讯作者：
Montresor, Marina
中科院分区：
文献类型：
--
作者：
Fuchs, Nike;Scalco, Eleonora;Montresor, Marina
南极硅藻Fragilariopsis kerguelensis在南大洋的地球化学循环中起着重要作用，其硅藻壳的遗骸形成了世界上最大的生物硅存款。我们评估了26株的遗传特性，从细胞收集在不同的网站在南大洋，使用三个分子标记，LSU和ITS rDNA和rbcL。供试菌株的LSU序列完全相同，ITS序列高度相似，rbcL序列仅存在一个碱基对的差异。这些结果，以及大量成功的交配实验表明，菌株属于单一的生物物种。本文研究了黑腹叶蝉的交配系统和生活史特征。kerguelensis。克隆株的细胞体积逐渐减小。配子形成只发生在相反的交配型菌株-细胞大小范围为7-36 μ m -混合在一起。两个双核配子形成在每个配子囊和配子接合产生一个合子，有四个核，被薄硅质鳞片包围。随后，四个核中的两个退化，受精卵膨胀形成由横向和纵向周层包围的子实体。荧光染料PDMPO染色首次提供了一个清晰的证明，纵向perizonium形成后，辅助孢子扩展完成。在成熟的子实体内产生的初始细胞的长度为78-101 μ m。许多作者已经表明，F. kerguelensis在具有不同初级生产系统的区域和季节收集的沉积物样品中存在差异，因此，该参数被提议作为古生产力的生物代用指标。更好地了解F的生命周期。kerguelensis应该有助于设计未来的调查，旨在测试自然环境中细胞大小分布与环境因素在调节群体细胞大小方面可能发挥的作用之间的联系。
The planktonic diatom Fragilariopsis kerguelensis plays an important role in the biogeochemical cycles of the Southern Ocean, where remains of its frustules form the largest deposit of biogenic silica anywhere in the world. We assessed the genetic identity of 26 strains, from cells collected at various sites in the Southern Ocean, using three molecular markers, LSU and ITS rDNA and rbcL. The LSU sequences were identical among the tested strains, ITS sequences were highly similar, and only one base pair difference was detected among the rbcL sequences. These results, together with a large number of successful mating experiments demonstrated that the strains belong to a single biological species. We investigated the mating system and life cycle traits of F. kerguelensis. Cell size diminished gradually in clonal strains. Gamete formation only occurred when strains of opposite mating type - within a cell size range of 7-36 mu m - were mixed together. Two binucleate gametes were formed in each gametangium and gamete conjugation produced a zygote that had four nuclei and was surrounded by thin siliceous scales. Two out of the four nuclei subsequently degenerated and the zygote expanded to form an auxospore surrounded by a transverse and a longitudinal perizonium. Staining with the fluorochrome PDMPO provided for the first time a clear demonstration that the longitudinal perizonium is formed after auxospore expansion is complete. Initial cells produced within the mature auxospores were 78-101 mu m in length. Various authors have shown that the average valve size of F. kerguelensis varies in sediment samples collected in regions and seasons with different primary production regimes and this parameter has thus been proposed as a biological proxy for palaeo-productivity. A better understanding of the life cycle of F. kerguelensis should help the design of future investigations aimed at testing the link between cell size distribution in the natural environment and the role that environmental factors might have in the regulation of population cell size.