Abstract
In general, the core subunits of a bacterial-type plastid RNA polymerase (PEP) are encoded by the plastid rpoA, rpoB, rpoC1 and rpoC2. However, an rpoA gene is absent from the moss Physcomitrella patens plastid genome but the nuclear counterparts, PpRpoA1 and PpRpoA2, are present in the nuclear genome. In the present study, we investigated differential expression of PpRpoA1 and PpRpoA2 in the protonemata grown under different light and dark conditions. The expression of PpRpoA2 was regulated in a light-dependent manner while PpRpoA1 was expressed at constant levels under different light/dark conditions. Disruption of PpRpoA1 gene resulted in the increase of PpRpoA2 transcript level. In addition, the transcript levels of several plastid genes significantly altered in the dark-adapted PpRpoA1 disruptant. We are currently investigating whether such a significant alteration of the transcript levels is caused by changes of transcription activity or mRNA stability.
