Abstract
Chloroplasts have their own genome and gene expression machineries derived from endosymbiosis of ancestral cyanobacteria. During subsequent evolution, chloroplasts lost their autonomy and most of regulatory function became under control of the nucleus. In this work, we used the primitive, unicellular red alga Cyanidioschyzon merolae. This alga shows ancestral characteristics on many aspects including chloroplast genome or transcription regulation. Therefore, some chloroplast functions in C. merolae can be partly regulated more autonomously than those in higher plants.
Here we performed run-on transcription assay using isolated chloroplasts to understand light-dependent transcription regulation in C.merolae chloroplasts. Transcription of every chloroplast gene was induced by light treatment of dark-adapted cells. On the other hand, transcription activity of ycf27 and psbD was specifically activated when isolated chloroplasts were shifted to the light after prepared from dark-grown cells. This result suggests that transcription of particular chloroplast genes is regulated by chloroplast-specific mechanisms independent of the nucleus.
