Functional Analysis Of The Chloroplast Division Protein FtsZ In Chlamydomonas Reinhardtii

Chloroplast as the only place of photosynthesis is the important organelles of plant cells. It is now accepted that chloroplast originated in the endosymbiotic event of the prokaryotes and primitive eukaryotes. Therefore the chloroplasts with the primitive photosynthetic bacteria have the same or similar division mechanism, which from the original primitive prokaryotes evolved into the power supply station of higher plants also has experienced a long process. In the process of evolution, FtsZ have been shifting from the chloroplast genome to nuclear genome,while the mechanism of the original MIN system to ensure that the correct positioning of FtsZ ring is still remaining. In addition, different from the bacterial cells,which only have one FtsZ gene, the plant’s FtsZ genes have evolved into two families——FtsZl and FtsZ2. Comparing their primary structure found that the conserved sequence of c-terminal of FtsZ2protein contained with bacteria are very similar, But it has not been found in the FtsZl protein.Many experiments also illustrates the FtsZ2and FtsZl proteins,lacking the c-terminal conservative sequence have different functions in the process of chloroplast divisions.Recently, Another study discovered the existence of new FtsZ family in the moss.We analyzed the introns of several species, including single-celled green algae——Chlamydomonas reinhardtii and found that the transfer of FtsZ was indeed following endosymbiotic event and happed before the differentiation of red algae and green algae or synchronized with their initial differentiation. After endosymbiotic event, a copy of FtsZ2evolved into the FtsZl,which is also consistent with the predecessors’research.At the same time, on the basis of laboratory’s previous experiments, we also constructed the RNAi and overexpression vectors in chlamydomonas. In the CrFtsZ2mutant, we observed abnormal division of chloroplasts-the half spherical chloroplast and cell growth slowed down, compared with wild type in the medium without carbon source. While in the CrFtsZl mutant, appeared the globular chloroplast, occupying most of the cell space and cells in culture medium without carbon source are not normal growth even appeared the phenomenon of cell death. So we speculate that in terms of influenceing chloroplast division, FtsZl,compared with FtsZ2gene,plays a more important role or it was endowed with the other function.The two genes maybe affect the growth of cells by influencing the photosynthesis. But those are just speculations and still need to be further proved.