Acts as a topological specificity factor during plastid division and specify plastid constriction sites (such as the Z-ring) in a MCD1-dependent manner (PubMed:29967285, PubMed:23936263). Especially involved in epidermal plastids division in a FTSZ1-dependent manner (PubMed:26500667). Required for the proper formation of FtsZ rings at the division site in nongreen plastids (e.g. etioplasts) (PubMed:23936263). May contribute to gravitropism in stems and hypocotyls. Stimulates MIND1 ATPase activity. In cooperation with MIND1, prevents FtsZ ring formation anywhere outside of the mid-plastids. Homodimer. Interacts with MIND1. These interactions are required for proper intraplastidic localization. Binds to ARC3. Dynamic protein that is restricted to a single spot at one end of chloroplasts or as two spots in close proximity normally towards one end of the chloroplast. Seems attached to membranes. Expressed in green tissues, especially at the shoot apex. Also present in leaves, stems, buds, and flowers, especially in sepals, siliques (tip and base), and anthers (mostly in pollen grains). Only one or two large plastids (all type of plastid) in each plastid containing cells (PubMed:23936263). Impaired gravitropism of inflorescence stems and hypocotyls, but not of roots. Wide variation in size and shape of epidermal plastids, occasionally displaying grape-like morphology, associated with a disturbed localization of FTSZ1 ring (PubMed:26500667). Severe inhibition of plastid division, producing motile disorganized dots and short filaments of FtsZ (PubMed:29967285). Reduced number of enlarged etioplasts in cotyledons associated with fragmented FtsZ filaments (PubMed:23936263). Altered localization of MCD1 and MinD1 in puncta on the envelope membranes of giant chloroplasts (PubMed:29967285). The mcd1 arc12 double mutant contains a heterogeneous population of chloroplasts, including some with multiple membrane constrictions associated with an organization of FtsZ1 in multiple rings similar to those observed in mcd1 single mutants (PubMed:29967285). Belongs to the MinE family.