Abstract
It is widely believed that chloroplast was generated by endosymbiosis of an ancient photosynthetic bacterium with an ancient eukaryotic cell.arc3 mutant of Arabidopsis thaliana is a chloroplast division mutant. ARC3 gene is a fusion gene of prokaryotic, FtsZ, and eukaryotic, phosphatidylinositol-4-phosphate 5-kinase (PIP5K), genes. ARC3 protein is exclusively located in chloroplast division ring as well as A. thaliana FtsZ. ARC3 protein was phosphorylated, similar to A. thaliana PIP5K, by A. thaliana protein in vitro and in vivo, and the phosphorylation rate using endogenous protein fraction from dark grown plant was higher than that from light grown plant, suggesting that light-dependent regulation of ARC3 via phosphorylation of PIP5K domain occurs in chloroplast division. Our results indicate that ARC3 is a functional prokaryotic and eukaryotic fusion protein, and suggest that ARC3 is a junction point in signal transduction through which the eukaryotic nucleus regulates prokaryotic chloroplast division.
