Shi Chao, Wang Shuo, Xia En-Hua, Jiang Jian-Jun, Zeng Fan-Chun, Gao Li-Zhi
Plant Germplasm and Genomics Center, Germplasm Bank of Wild Species in Southwest China, Kunming Institute of Botany, the Chinese Academy of Sciences, Kunming 650204, China.
University of the Chinese Academy of Sciences, Beijing 100039, China.
Sci Rep. 2016 Jul 26;6:30135. doi: 10.1038/srep30135.
Prokaryotes possess a simple genome transcription system that is different from that of eukaryotes. In chloroplasts (plastids), it is believed that the prokaryotic gene transcription features govern genome transcription. However, the polycistronic operon transcription model cannot account for all the chloroplast genome (plastome) transcription products at whole-genome level, especially regarding various RNA isoforms. By systematically analyzing transcriptomes of plastids of algae and higher plants, and cyanobacteria, we find that the entire plastome is transcribed in photosynthetic green plants, and that this pattern originated from prokaryotic cyanobacteria - ancestor of the chloroplast genomes that diverged about 1 billion years ago. We propose a multiple arrangement transcription model that multiple transcription initiations and terminations combine haphazardly to accomplish the genome transcription followed by subsequent RNA processing events, which explains the full chloroplast genome transcription phenomenon and numerous functional and/or aberrant pre-RNAs. Our findings indicate a complex prokaryotic genome regulation when processing primary transcripts.
原核生物拥有一个与真核生物不同的简单基因组转录系统。在叶绿体（质体）中，人们认为原核基因转录特征支配着基因组转录。然而，多顺反子操纵子转录模型无法在全基因组水平上解释所有叶绿体基因组（质体基因组）的转录产物，特别是关于各种RNA异构体。通过系统分析藻类、高等植物和蓝细菌的质体转录组，我们发现光合绿色植物的整个质体基因组都被转录，并且这种模式起源于原核蓝细菌——大约10亿年前分化的叶绿体基因组的祖先。我们提出了一种多重排列转录模型，即多个转录起始和终止随机组合以完成基因组转录，随后进行后续的RNA加工事件，这解释了完整的叶绿体基因组转录现象以及众多功能性和/或异常的前体RNA。我们的研究结果表明，在处理初级转录本时原核生物基因组存在复杂的调控。
