title: GIANT CHLOROPLAST 1 is essential for correct plastid division in Arabidopsis.
abstract: Plastids are vital plant organelles involved in many essential biological processes. Plastids are not created de novo but divide by binary fission mediated by nuclear-encoded proteins of both prokaryotic and eukaryotic origin. Although several plastid division proteins have been identified in plants, limited information exists regarding possible division control mechanisms. Here, we describe the identification of GIANT CHLOROPLAST 1 (GC1), a new nuclear-encoded protein essential for correct plastid division in Arabidopsis. GC1 is plastid-localized and is anchored to the stromal surface of the chloroplast inner envelope by a C-terminal amphipathic helix. In Arabidopsis, GC1 deficiency results in mesophyll cells harbouring one to two giant chloroplasts, whilst GC1 overexpression has no effect on division. GC1 can form homodimers but does not show any interaction with the Arabidopsis plastid division proteins AtFtsZ1-1, AtFtsZ2-1, AtMinD1, or AtMinE1. Analysis reveals that GC1-deficient giant chloroplasts contain densely packed wild-type-like thylakoid membranes and that GC1-deficient leaves exhibit lower rates of CO(2) assimilation compared to wild-type. Although GC1 shows similarity to a putative cyanobacterial SulA cell division inhibitor, our findings suggest that GC1 does not act as a plastid division inhibitor but, rather, as a positive factor at an early stage of the division process.
authors.affiliation: Department of Biology, University of Leicester, Leicester LE1 7RH, United Kingdom.
authors.forename: Jodi
authors.initials: J
authors.lastname: Maple
authors.forename: Makoto T
authors.initials: MT
authors.lastname: Fujiwara
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Kitahata
authors.forename: Tracy
authors.initials: T
authors.lastname: Lawson
authors.forename: Neil R
authors.initials: NR
authors.lastname: Baker
authors.forename: Shigeo
authors.initials: S
authors.lastname: Yoshida
authors.forename: Simon Geir
authors.initials: SG
authors.lastname: Møller
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000502:physiology*; D001483:Base Sequence; D015152:Blotting, Northern; D002736:Chloroplasts / Q000235:genetics* / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D016000:Cluster Analysis; D017931:DNA Primers; D018506:Gene Expression Regulation, Plant; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010788:Photosynthesis / Q000502:physiology; D010802:Phylogeny; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D017931:DNA Primers