Split Photosystem Protein, Linear-Mapping Topology, and Growth of Structural Complexity in the Plastid Genome of Chromera velia
Split Photosystem Protein, Linear-Mapping Topology, and Growth of Structural Complexity in the Plastid Genome of Chromera velia
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DOI：
10.1093/molbev/mst144
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发表时间：
2013-11-01
影响因子：
10.7
通讯作者：
Keeling, Patrick J.
中科院分区：
文献类型：
--
作者：
Janouskovec, Jan;Sobotka, Roman;Keeling, Patrick J.
典型的光合叶绿体基因组由一个单一的循环作图染色体组成，该染色体编码一个高度保守的蛋白质核心，参与光合作用和ATP的产生。在这里，我们证明了顶端复合体的光合作用近亲Chromera Velia的叶绿体基因组在几个独特的方面偏离了这一观点。核心光合作用蛋白psaA和AtpB被分成两个片段，我们发现这两个片段是独立转录、寡核苷酸尾部、翻译和组装成功能性光系统I和ATP合成酶复合体的。全基因组转录图谱支持许多其他高度修饰的蛋白质的表达，包括几个含有数百个氨基酸长度的延伸。典型的基因簇和操纵子已经被碎片化并重新洗牌成新的假定转录单位。大量的基因组对末端阅读，再加上脉冲场凝胶电泳和聚合酶链式反应，一致地表明绒毛藻的基因组是线性作图的，这是所有质体中的一个独特状态。大量的基因组内复制可能是由重组所介导的，可以解释蛋白质的分裂、延伸和基因组线性化，并且可能是许多特征背后的关键驱动力，这些特征违背了叶绿体基因组结构和功能的传统方式。
The canonical photosynthetic plastid genomes consist of a single circular-mapping chromosome that encodes a highly conserved protein core, involved in photosynthesis and ATP generation. Here, we demonstrate that the plastid genome of the photosynthetic relative of apicomplexans, Chromera velia, departs from this view in several unique ways. Core photosynthesis proteins PsaA and AtpB have been broken into two fragments, which we show are independently transcribed, oligoU-tailed, translated, and assembled into functional photosystem I and ATP synthase complexes. Genome-wide transcription profiles support expression of many other highly modified proteins, including several that contain extensions amounting to hundreds of amino acids in length. Canonical gene clusters and operons have been fragmented and reshuffled into novel putative transcriptional units. Massive genomic coverage by paired-end reads, coupled with pulsed-field gel electrophoresis and polymerase chain reaction, consistently indicate that the C. velia plastid genome is linear-mapping, a unique state among all plastids. Abundant intragenomic duplication probably mediated by recombination can explain protein splits, extensions, and genome linearization and is perhaps the key driving force behind the many features that defy the conventional ways of plastid genome architecture and function.