FtsZ1 and FtsZ2 are phylogenetically distinct homologues of the tubulin-like bacterial cell division protein FtsZ that play major roles in the initiation and progression of plastid division in plant cells. Both proteins are components of a mid-plastid ring, the Z-ring, which functions as a contractile ring on the stromal surface of the chloroplast IEM (inner envelope membrane). FtsZ1 and FtsZ2 have been shown to interact, but their in vivo biochemical properties are largely unknown. To gain insight into the in vivo biochemical relationship between FtsZ1 and FtsZ2, in the present study we investigated their molecular levels in wild-type Arabidopsis thaliana plants and endogenous interactions in Arabidopsis and pea. Quantitative immunoblotting and morphometric analysis showed that the average total FtsZ concentration in chloroplasts of 3-week-old Arabidopsis plants is comparable with that in Escherichia coli. FtsZ levels declined as plants matured, but the molar ratio between FtsZ1 and FtsZ2 remained constant at approx. 1:2, suggesting that this stoichiometry is regulated and functionally important. Density-gradient centrifugation, native gel electrophoresis, gel filtration and co-immunoprecipitation experiments showed that a portion of the FtsZ1 and FtsZ2 in Arabidopsis and pea chloroplasts is stably associated in a complex of ∼200–245 kDa. This complex also contains the FtsZ2-interacting protein ARC6 (accumulation and replicatioin of chloroplasts 6), an IEM protein, and analysis of density-gradient fractions suggests the presence of the FtsZ1-interacting protein ARC3. Based on the mid-plastid localization of ARC6 and ARC3 and their postulated roles in promoting and inhibiting chloroplast FtsZ polymer formation respectively, we hypothesize that the FtsZ1–FtsZ2–ARC3–ARC6 complex represents an unpolymerized IEM-associated pool of FtsZ that contributes to the dynamic regulation of Z-ring assembly and remodelling at the plastid division site in vivo.
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Research Article|
May 14 2008
In vivo quantitative relationship between plastid division proteins FtsZ1 and FtsZ2 and identification of ARC6 and ARC3 in a native FtsZ complex
Rosemary S. Mcandrew;
Rosemary S. Mcandrew
1
*Department of Plant Biology, Michigan State University, East Lansing, MI 48824, U.S.A.
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Bradley J. S. C. Olson;
Bradley J. S. C. Olson
1
*Department of Plant Biology, Michigan State University, East Lansing, MI 48824, U.S.A.
†The Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, U.S.A.
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Deena K. Kadirjan-Kalbach;
Deena K. Kadirjan-Kalbach
*Department of Plant Biology, Michigan State University, East Lansing, MI 48824, U.S.A.
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Cecilia L. Chi-Ham;
Cecilia L. Chi-Ham
2
*Department of Plant Biology, Michigan State University, East Lansing, MI 48824, U.S.A.
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Stanislav Vitha;
Stanislav Vitha
3
*Department of Plant Biology, Michigan State University, East Lansing, MI 48824, U.S.A.
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John E. Froehlich;
John E. Froehlich
‡Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, U.S.A.
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Katherine W. Osteryoung
Katherine W. Osteryoung
4
*Department of Plant Biology, Michigan State University, East Lansing, MI 48824, U.S.A.
4To whom correspondence should be addressed (email osteryou@msu.edu).
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Publisher: Portland Press Ltd
Received:
October 02 2007
Revision Received:
February 12 2008
Accepted:
February 19 2008
Accepted Manuscript online:
February 19 2008
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© The Authors Journal compilation © 2008 Biochemical Society
2008
Biochem J (2008) 412 (2): 367–378.
Article history
Received:
October 02 2007
Revision Received:
February 12 2008
Accepted:
February 19 2008
Accepted Manuscript online:
February 19 2008
Citation
Rosemary S. Mcandrew, Bradley J. S. C. Olson, Deena K. Kadirjan-Kalbach, Cecilia L. Chi-Ham, Stanislav Vitha, John E. Froehlich, Katherine W. Osteryoung; In vivo quantitative relationship between plastid division proteins FtsZ1 and FtsZ2 and identification of ARC6 and ARC3 in a native FtsZ complex. Biochem J 1 June 2008; 412 (2): 367–378. doi: https://doi.org/10.1042/BJ20071354
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