Plant and Cell Physiology Advance Access originally published online on April 27, 2007
Plant and Cell Physiology 2007 48(6):775-791; doi:10.1093/pcp/pcm049
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Effects of Mutations in Arabidopsis FtsZ1 on Plastid Division, FtsZ Ring Formation and Positioning, and FtsZ Filament Morphology in Vivo
1Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA
2Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
3Department of Biology, Indiana University, Bloomington, IN 47405, USA
*Corresponding author: E-mail, osteryou{at}msu.edu; Fax, +1-517-353-1926.
| Abstract |
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In plants, chloroplast division FtsZ proteins have diverged into two families, FtsZ1 and FtsZ2. FtsZ1 is more divergent from its bacterial counterparts and lacks a C-terminal motif conserved in most other FtsZs. To begin investigating FtsZ1 structurefunction relationships, we first identified a T-DNA insertion mutation in the single FtsZ1 gene in Arabidopsis thaliana, AtFtsZ1-1. Homozygotes null for FtsZ1, though impaired in chloroplast division, could be isolated and set seed normally, indicating that FtsZ1 is not essential for viability. We then mapped five additional atftsZ1-1 alleles onto an FtsZ1 structural model and characterized chloroplast morphologies, FtsZ protein levels and FtsZ filament morphologies in young and mature leaves of the corresponding mutants. atftsZ1-1(G267R), atftsZ1-1(R298Q) and atftsZ1-1(
404433) exhibit reduced FtsZ1 accumulation but wild-type FtsZ2 levels. The semi-dominant atftsZ1-1(G267R) mutation caused the most severe phenotype, altering a conserved residue in the predicted T7 loop. atftsZ1-1(G267R) protein accumulates normally in young leaves but is not detected in rings or filaments. atftsZ1-1(R298Q) has midplastid FtsZ1-containing rings in young leaves, indicating that R298 is not critical for ring formation or positioning despite its conservation. atftsZ1-1(D159N) and atftsZ1-1(G366A) both have overly long, sometimes spiral-like FtsZ filaments, suggesting that FtsZ dynamics are altered in these mutants. However, atftsZ1-1(D159N) exhibits loss of proper midplastid FtsZ positioning while atftsZ1-1(G366A) does not. Finally, truncation of the FtsZ1 C-terminus in atftsZ1-1(
404433) impairs chloroplast division somewhat but does not prevent midplastid Z ring formation. These alleles will facilitate understanding of how the in vitro biochemical properties of FtsZ1 are related to its in vivo function.
Keywords: arc10 - FtsZ - pmi4
Abbreviations: arc, accumulation and replication of chloroplasts; CAPS, cleaved amplified polymorphic sequences; CTD, C-terminal domain; DIC, differentail interference contrast; EMS, ethylmethane sulfonate; FITC, fluorescein isothiocyanate; pmi, plastid mobility impaired; NTD, N-terminal domain; RTPCR, reverse transcriptionPCR; SSLP, simple sequence length polymorphism.
4These authors contributed equally to this work.
5Present address: Miyagishima Initiative Research Unit, Frontier Research System, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198 Japan.
6Present address: Department of Microbiology, The State University of New York, Stony Brook, NY 11794, USA.
(Received January 4, 2007; Accepted April 17, 2007)
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