Together with MIND1 and MCD1, regulates FtsZ ring positioning in chloroplasts in an ARC6-dependent manner (PubMed:29967285). Z-ring accessory protein involved in the initiation of plastid division and division site placement (might functionally replace bacterial MinC) (PubMed:23936263). Acts as a disassembly factor that accelerates fragmentation and depolymerization of existing FtsZ2 filaments by enhancing FTSZ2 GTPase activity, thus leading to the conversion of FTSZ2 bound GTP into GDP, a process which triggers FtsZ2 filaments destabilization (PubMed:29138260, PubMed:25731613). Prevents misplaced Z-ring formation at chloroplast stroma nondivision sites (PubMed:30824505). May control the rate of chloroplast expansion. Seems to influence stromule (stroma-filled tubular extensions of the plastid envelope membrane) length and frequency. Self-interacts. Interacts with FTSZ, CDP1/PARC6 (via N-terminus), MIND1 and MINE1 (PubMed:26527658, PubMed:30824505). Part of a complex made of ARC3, ARC6, FTSZ1 and FTSZ2 (PubMed:30824505). Recruited to the middle of the plastid by CDP1/PARC6 where subsequent complex made of CDP1/PARC6, ARC3 and FtsZ proteins can form; this complex enhances the dynamics of Z rings during chloroplast division (PubMed:30824505). Binding to FTSZ2-1 is enabled by ARC6 (PubMed:29138260). Distributed in two pools, a first one throughout the stroma, probably to inhibits Z-ring assembly at nondivision sites, and a second one localized to a midplastid ring-like structure (PubMed:30824505). Located at the site of chloroplast division on the outer surface in a ring-shaped structure at the early and middle stages of the process according to PubMed:15356321. Forms ring-like structures, short filaments and discrete foci in the chloroplast stroma according to PubMed:17304239 (PubMed:17304239, PubMed:15356321). MORN domains promote interaction with ARC6 and CDP1/PARC6 but prevent binding to FTSZ1, FTSZ2, MIND and MINE proteins. Small number of abnormally large and heterogeneous chloroplasts sometimes exhibiting alteration in stromule length and frequency in non-green tissues (e.g. slightly increased stromule frequency in hypocotyl epidermal cells) (PubMed:30824505, PubMed:23936263). Normal shape and number of etioplasts in cotyledons (PubMed:23936263). Misexpression and mislocalization of ADT2 (PubMed:30252596). Formation of multiple MCD1 and MIND1-containing ring structures in dividing chloroplasts, instead of single ring (PubMed:29967285). Slow trunover of FtsZ ring subunits (e.g. FTSZ2-1, FTSZ2-2 and FTSZ1) in contractile rings at the chloroplast midpoint (PubMed:25731613). Intron retention.