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首页> 外文期刊>Phycological Research >Multiple losses of photosynthesis in Nitzschia (Bacillariophyceae)
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Multiple losses of photosynthesis in Nitzschia (Bacillariophyceae)

机译：尼茨菌（芽孢杆菌科）光合作用的多次丧失

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摘要

In order to obtain insights into the evolution of colorless (apochlorotic) diatoms, we investigated newly established apochlorotic strains of Nitzschia spp. using light and electron microscopy and molecular phylogenetic analyses. Fluorescence microscopic observations demonstrated that the apochlorotic diatoms lack chlorophylls. Transmission electron microscopy of two apochlorotic strains also demonstrated that their plastids lacked thylakoids; instead, having four-membrane-bound organelles without thylakoids, similar to nonphotosynthetic plastid remnants. From the apochlorotic strains, we also found plastid small subunit rRNA genes that were unusually long branched in phylogenetic analyses, as observed in other nonphotosynthetic plastids. Molecular phylogenetic analysis of the nucleus-encoded large subunit rRNA genes showed eight distinct lineages for apochlorotic diatoms. The eight apochlorotic lineages were not monophyletic, suggesting that the loss of photosynthesis took place multiple times independently within Nitzschia. Several diatoms, including Nitzschia spp., are mixotrophic, which is an expected mode of nutrition that would help explain the evolutionary switch from a photosynthetic lifestyle to a heterotrophic lifestyle.
机译：为了获得对无色（脱氯）硅藻的进化的见解，我们调查了新建立的Nitzschia spp的脱氯菌株。使用光电子显微镜和分子系统发育分析。荧光显微镜观察表明脱辅基硅藻缺乏叶绿素。两种脱辅氯霉素菌株的透射电子显微镜也表明它们的质体缺乏类囊体。相反，它具有四膜结合的细胞器而没有类囊体，类似于非光合质体残余物。从脱氯霉素菌株中，我们还发现了质体小亚基rRNA基因，在系统发育分析中异常长的分支，如在其他非光合质体中观察到的。分子编码的大亚基rRNA基因的分子系统发育分析显示了脱绿硅藻的八个不同谱系。八种脱磷世系不是单系的，这表明光合作用的丧失在尼采内独立发生了多次。混合营养（Nitzschia spp。）等几种硅藻是营养混合型，这是一种预期的营养模式，将有助于解释从光合生活方式向异养生活方式的进化转变。

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