Abstract
Chloroplasts genes are transcribed by the plastid-encoded (PEP) and the nuclear-encoded (NEP) plastid RNA polymerase in higher plants. The core subunits of PEP are encoded by the plastid rpoA, rpoB, rpoC1 and rpoC2. However, rpoA gene is absent in the moss Physcomitrella patens plastid genome but the nuclear counterpart, PpRpoA, is present in the nuclear genome. This suggests that the P. patens PEP is distinct from the PEP of higher plants. In this study, we generated and characterized the PpRpoA knockout moss to examine whether either PEP or NEP, or both occur in transcription of plastid genes in P. patens. To address the question we performed the plastid DNA microarray analysis, run-on transcription assay, and in vitro plastid transcription assay. The data indicated that PEP and NEP occur in transcription of plastid genes in P. patens and both enzymes recognize the promoters in a different manner from higher plant enzymes.
