Principles of plastid reductive evolution illuminated by nonphotosynthetic chrysophytes
Principles of plastid reductive evolution illuminated by nonphotosynthetic chrysophytes
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DOI：
10.1073/pnas.1819976116
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发表时间：
2019-04-02
影响因子：
11.1
通讯作者：
Kamikawa, Ryoma
中科院分区：
文献类型：
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作者：
Dorrell, Richard G.;Azuma, Tomonori;Kamikawa, Ryoma
生命分为生产者和消费者的划分因进化而变得模糊。例如，真核光养生物可能会失去光合作用的能力，尽管它们可能会保留执行其他基本细胞功能的退化体。金藻经历了特别大量的光合作用损失。在这里，我们展示了一种非光合作用的黄藻“SpumeIla”sp.的质体基因组序列。Nies-1846，并表明它保留了一组与顶复合体寄生虫几乎相同的叶绿体编码功能。我们对12个不同的光合型和非光合型黄藻谱系的转录分析表明，这些非光合体的功能显著趋同，并伴随着信息性的谱系特有的保留和丢失。在一种极端情况下，丛枝杆菌保留了许多与光合作用相关的蛋白质，尽管它似乎失去了还原的戊糖磷酸途径和大多数叶绿体氨基酸代谢途径。在另一个极端，副单胞菌缺乏与基因表达相关的叶绿体靶标蛋白和所有需要叶绿体编码伙伴的代谢途径，这表明该属中的叶绿体DNA完全丧失。耐人寻味的是，一些曾经在副金黄色葡萄球菌质体基因组的表达中起作用的核编码蛋白被保留了下来。这些蛋白很可能是针对金藻祖先的叶绿体和线粒体的双重靶标，并且是唯一针对副金藻线粒体的靶标。我们的比较分析提供了对非光合体功能减少过程的洞察。
The division of life into producers and consumers is blurred by evolution. For example, eukaryotic phototrophs can lose the capacity to photosynthesize, although they may retain vestigial plastids that perform other essential cellular functions. Chrysophyte algae have undergone a particularly large number of photosynthesis losses. Here, we present a plastid genome sequence from a nonphotosynthetic chrysophyte, "SpumeIla" sp. NIES-1846, and show that it has retained a nearly identical set of plastid-encoded functions as apicomplexan parasites. Our transcriptomic analysis of 12 different photosynthetic and nonphotosynthetic chrysophyte lineages reveals remarkable convergence in the functions of these non-photosynthetic plastids, along with informative lineage-specific retentions and losses. At one extreme, Cornospumella fuschlensis retains many photosynthesis-associated proteins, although it appears to have lost the reductive pentose phosphate pathway and most plastid amino acid metabolism pathways. At the other extreme, Paraphysomonas lacks plastid-targeted proteins associated with gene expression and all metabolic pathways that require plastidencoded partners, indicating a complete loss of plastid DNA in this genus. Intriguingly, some of the nucleus-encoded proteins that once functioned in the expression of the Paraphysomonas plastid genome have been retained. These proteins were likely to have been dual targeted to the plastid and mitochondria of the chrysophyte ancestor, and are uniquely targeted to the mitochondria in Paraphysomonas. Our comparative analyses provide insights into the process of functional reduction in nonphotosynthetic plastids.