Abstract
Chloroplasts have their own DNA and gene expression systems that are derived from endosymbiosis of ancestral cyanobacteria. However, during long history of evolution, chloroplasts lost their autonomy and most of regulatory system became under control of the nucleus. In this work, we used the primitive, unicellular red alga Cyanidioschyzon merolae, which shows ancestral characteristics on many aspects including chloroplast genome and transcription systems. Therefore, gene expression in C. merolae chloroplasts can be regulated more autonomously than that in higher plants.
We previously found that the chloroplast two-component system, which is composed of the unique histidine kinase (HIK) and one of chloroplast-encoded response regulators (Ycf27), is involved in this regulation. In this work, we further analyzed function of HIK. Expression level of HIK was constant in various light conditions, suggesting that activity of HIK could be regulated post-translationally. Including other data as well as structural characteristics of HIK, the system for light-responsive transcription regulation in C. merolae chloroplasts will be discussed.
