Data_Sheet_3_Comparative Plastid Genomics of Green-Colored Dinoflagellates Unveils Parallel Genome Compaction and RNA Editing.PDF

Dinoflagellates possess plastids that are diverse in both pigmentation and evolutionary background. One of the plastid types found in dinoflagellates is pigmented with chlorophylls a and b (Chl a + b) and originated from the endosymbionts belonging to a small group of green algae, Pedinophyceae. The Chl a + b-containing plastids have been found in three distantly related dinoflagellates Lepidodinium spp., strain MGD, and strain TGD, and were proposed to be derived from separate partnerships between a dinoflagellate (host) and a pedinophycean green alga (endosymbiont). Prior to this study, a plastid genome sequence was only available for L. chlorophorum, which was reported to bear the features that were not found in that of the pedinophycean green alga Pedinomonas minor, a putative close relative of the endosymbiont that gave rise to the current Chl a + b-containing plastid. In this study, we sequenced the plastid genomes of strains MGD and TGD to compare with those of L. chlorophorum as well as pedinophycean green algae. The mapping of the RNA-seq reads on the corresponding plastid genome identified RNA editing on plastid gene transcripts in the three dinoflagellates. Further, the comparative plastid genomics revealed that the plastid genomes of the three dinoflagellates achieved several features, which are not found in or much less obvious than the pedinophycean plastid genomes determined to date, in parallel.甲藻拥有的质体在色素组成与演化背景上均呈现出多样性。甲藻中存在一类携带叶绿素a和b（Chl a + b）的质体，其起源于隶属于小型绿藻类群扁藻纲（Pedinophyceae）的内共生体。目前已在三类亲缘关系较远的甲藻——鳞孔藻属（Lepidodinium）物种、菌株MGD与菌株TGD中发现此类含Chl a + b的质体，且研究推测它们均源自甲藻（宿主）与扁藻纲绿藻（内共生体）之间独立形成的共生关系。在本研究开展前，仅绿孢鳞孔藻（L. chlorophorum）的质体基因组序列已被公开报道；据文献记载，该质体基因组具备小佩迪诺藻（Pedinomonas minor，一种被认为是该共生事件起源内共生体的推定近缘类群）的质体基因组所不具有的特征。本研究对菌株MGD与TGD的质体基因组进行了测序，以期与绿孢鳞孔藻以及扁藻纲绿藻的质体基因组开展比较分析。通过将RNA测序读段比对至对应质体基因组，我们在这三类甲藻的质体基因转录本中检测到了RNA编辑现象。进一步的比较质体基因组学分析显示，三类甲藻的质体基因组独立演化出了多项迄今已测序扁藻纲质体基因组中未出现、或仅以极微弱形式存在的特征。