Plant and Cell Physiology Advance Access published online on April 27, 2007
Plant and Cell Physiology, 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
1 Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA
2 Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
3 Department of Biology, Indiana University, Bloomington, Indiana 47405, USA
Corresponding author: Katherine W. Osteryoung. Department of Plant Biology, 166 Plant Biology Bldg. #339 Michigan State University,East Lansing, MI 48824-1312, Office: 517-355-4685, FAX: 517-353-1926, E-mail: osteryou{at}msu.edu
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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 structure-function 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 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(
404-433) 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 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 Z-filaments, suggesting 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(404-433) 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
* These authors contributed equally to the development of this manuscript
Initiative Research Unit, Frontier Research System, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
Department of Microbiology, The State University of New York, Stony Brook, New York 11794, USA
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