ARC3, Chloroplast Division Factor, Is A Prokaryotic And Eukaryotic Fusion Protein

Abstract

It is widely believed that chloroplast was generated by endosymbiosis of ancient photosynthetic bacterium into ancient eukaryotic cell. arc3 (Accumulation and Replication of Chloroplast) mutant of Arabidopsis thaliana has a few abnormally large chloroplasts in cell. Fine mapping analyses showed ARC3 gene is a fusion gene of prokaryotic, FtsZ, and eukaryotic, phosphatidylinositol-4-phosphate 5-kinase (PIP5K), genes. The fusion protein of the full-length ARC3 and GFP (Green fluorescent protein) was located exclusively in chloroplast. The PIP5K activity of ARC3 protein was not detected. The ARC3 protein, however is phosphorylated by A. thaliana protein in vitro. These results show that ARC3 is a functional prokaryotic and eukaryotic fusion protein, and is a linkage point in the signal transduction by which eukaryotic nucleus regulates prokaryotic chloroplast division.