title: Chloroplast division protein ARC3 regulates chloroplast FtsZ-ring assembly and positioning in arabidopsis through interaction with FtsZ2.
abstract: Chloroplast division is initiated by assembly of a mid-chloroplast FtsZ (Z) ring comprising two cytoskeletal proteins, FtsZ1 and FtsZ2. The division-site regulators ACCUMULATION AND REPLICATION OF CHLOROPLASTS3 (ARC3), MinD1, and MinE1 restrict division to the mid-plastid, but their roles are poorly understood. Using genetic analyses in Arabidopsis thaliana, we show that ARC3 mediates division-site placement by inhibiting Z-ring assembly, and MinD1 and MinE1 function through ARC3. ftsZ1 null mutants exhibited some mid-plastid FtsZ2 rings and constrictions, whereas neither constrictions nor FtsZ1 rings were observed in mutants lacking FtsZ2, suggesting FtsZ2 is the primary determinant of Z-ring assembly in vivo. arc3 ftsZ1 double mutants exhibited multiple parallel but no mid-plastid FtsZ2 rings, resembling the Z-ring phenotype in arc3 single mutants and showing that ARC3 affects positioning of FtsZ2 rings as well as Z rings. ARC3 overexpression in the wild type and ftsZ1 inhibited Z-ring and FtsZ2-ring assembly, respectively. Consistent with its effects in vivo, ARC3 interacted with FtsZ2 in two-hybrid assays and inhibited FtsZ2 assembly in a heterologous system. Our studies are consistent with a model wherein ARC3 directly inhibits Z-ring assembly in vivo primarily through interaction with FtsZ2 in heteropolymers and suggest that ARC3 activity is spatially regulated by MinD1 and MinE1 to permit Z-ring assembly at the mid-plastid.
authors.affiliation: Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Schmitz
authors.forename: Deena K
authors.initials: DK
authors.lastname: Kadirjan-Kalbach
authors.forename: Allan D
authors.initials: AD
authors.lastname: Terbush
authors.forename: Katherine W
authors.initials: KW
authors.lastname: Osteryoung
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D008856:Microscopy, Fluorescence; D009154:Mutation; D030821:Plants, Genetically Modified; D058105:Polymerization; D011485:Protein Binding; D020798:Two-Hybrid System Techniques
chemical_list: C493630:ARC3 protein, Arabidopsis; D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; C095113:FTSZ protein, Arabidopsis; C523306:FtsZ1 protein, Arabidopsis; C465003:MinE1 protein, Arabidopsis; D000251:Adenosine Triphosphatases; C505156:MinD1 protein, Arabidopsis