Molecular architecture and discontinuous evolution of plastid genomic machinery

点击翻译按钮获取中文摘要

The following lines of evidence support our hypothesis on the discontinuous evolution of plastid genomic machinery.1. T7-type RNA polymerase (RPOT) is localized to only mitochondria. In angiosperms, the RPOT gene was duplicated to produce plastid-localyzed isozyme.2. PEND protein is a DNA-binding protein principally localized to developing plastids. In wounded tissues, this protein is also localized in the nucleus. This protein is only present in angiosperms, and therefore supposed to be newly added transcription factor in angiosperms.3. Sulfite reductase (SiR) is a major DNA-binding protein in the nucleoids of pea chloroplasts. The cDNA encoding SiR was isolated from pea. In the moss Physcomitrella patens, SiR was also a major component of plastid nucleoids. In red algal plastids and cyanobacteria, SiR was detected in the nucleoids, but was not the major component. This suggests that the major DNA-binding protein of nucleoid has been replaced during the evolution of plastids.4. Protein phosphorylation is involved in the regulation of transcription in plastid nucleoids.5. Computer-assisted analysis revealed a large number of plastid proteins that are supposed to originate from cyanobacterial endosymbionts.