Chloroplast targeting, distribution and transcriptional fluctuation of AtMinD1, a eubacteria-type factor critical for chloroplast division

In Arabidopsis thaliana, a mature mesophyll cell contains approximately 100 chloroplasts. Although 12 are mutants (accumulation and replication of chl oroplasts) and two chloroplast division genes homologous to eubacterial fts Z have been isolated from A, thaliana, the molecular mechanism underlying t he chloroplast division is still unclear, We characterized AtMinD1, a eubac terial minD homolog, for chloroplast division in A. thaliana, AtMinD1-green fluorescent protein targeted to the chloroplasts and possibly associated w ith the envelope membranes in vivo. During the seed germination, the AtMinD 1 transcripts were accumulated twice, just after release from cold treatmen t and at the beginning of rapid greening, in similar fashion to AtFtsZs. Fu rthermore the transcript level in a severest chloroplast division mutant, a rc6, was 3-5-fold higher than that in wild-type.