Genetic Mapping and Analysis of a Chloroplast Division Mutant cpd111 in Arabidopsis thaliana Localization of Two GFP-tagged Tobacco Plastid Division Protein NtFtsZs in Escherichia coli Expression and Localization of FtsZ from Spirulina platensis in Escherichia coli Cloning of FtsZ Gene Fragments from Acer negundo,Constructing of RNAi Vectors and Its Transient Expression in Tobacco Expression of Chlamydomonas reinhardtii chloroplast division gene CrFtsZ1 in E.coli Effects of Tobacco Plastid Division Genes NtFtsZ1 and NtFtsZ2 on the Division and Morphology of Chloroplasts