The unicellular, free-living, nonphotosynthetic chlorophycean alga Polytomella parva, closely related to Chlamydomonas reinhardtii and Volvox carteri, contains colorless, starch-storing plastids. The P. parva plastids lack all light-dependent processes but maintain crucial metabolic pathways. The colorless alga also lacks a plastid genome, meaning no transcription or translation should occur inside the organelle. Here, using an algal fraction enriched in plastids as well as publicly available transcriptome data, we provide a morphological and proteomic characterization of the P. parva plastid, ultimately identifying several plastid proteins, both by mass spectrometry and bioinformatic analyses. Data are available via ProteomeXchange with identifier PXD022051. Altogether these results led us to propose a plastid proteome for P. parva, i.e., a set of proteins that participate in carbohydrate metabolism; in the synthesis and degradation of starch, amino acids and lipids; in the biosynthesis of terpenoids and tetrapyrroles; in solute transport and protein translocation; and in redox homeostasis. This is the first detailed plastid proteome from a unicellular, free-living colorless alga.

该单细胞，自由生活，非光合藻类绿藻Polytomella麦穗鱼，密切相关的衣藻和团藻carteri，包含无色，淀粉质存储。该P.麦穗鱼质缺乏所有依赖于光的过程，但维持关键的代谢途径。无色藻类也缺乏质体基因组，这意味着细胞器内部不应发生转录或翻译。在这里，使用富含质体的藻类馏分以及可公开获得的转录组数据，我们提供了P. parva的形态学和蛋白质组学表征质体，通过质谱和生物信息学分析最终鉴定出几种质体蛋白。数据可通过ProteomeXchange获得，其标识符为PXD022051。总而言之，这些结果使我们提出了一种用于P. parva的质体蛋白质组，即一组参与碳水化合物代谢的蛋白质。淀粉，氨基酸和脂质的合成和降解；在萜类和四吡咯的生物合成中；溶质运输和蛋白质易位；和氧化还原稳态。这是来自单细胞，自由生活的无色藻类的第一个详细的质体蛋白质组。