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Professor of Plant Biology
Department of Plant Biology
Plant Biology Department
Selected Recent Publications; Publication List; Current Funding; Teaching; Lab Members |
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Research
RESEARCH PROGRAM: COMPOSITION, ARCHITECTURE AND BIOCHEMICAL DYNAMICS OF THE PLASTID DIVISION APPARATUS IN PLANTS
Chloroplast division in plant cells involves a complicated series of membrane remodeling events, including the concerted constriction of two envelope membranes, the fusion of the four lipid bilayers late in division, the final separation of the two daughter organelles, and possibly the resolution of the fused membranes back into two discrete bilayers. These processes are orchestrated by a dynamic macromolecular machine composed of at least four ring-shaped subcomplexes positioned both inside and outside the organelle (Figure 1). The proteins comprising these structures must be recruited to and properly assembled at the division site and their biochemical activities coordinated across the two envelope membranes to achieve constriction of the organelle and severing of the daughter plastids. Studies from our laboratory have revealed that the division apparatus is evolutionarily as well as topologically complex, containing proteins derived from both the cyanobacterial endosymbiont from which chloroplasts descended and from the eukaryotic host. Using Arabidopsis thaliana and cyanobacteria as complementary model systems, we are employing the tools of genetics, genomics, molecular biology, biochemistry and cell biology to identify all the components of the plastid division apparatus and define their biochemical functions. Our long-term goal is to fully understand the biochemical mechanisms and regulatory processes that govern the activity of the chloroplast division machinery in plants.
Figure 1. Steps in chloroplast division
A few of the chloroplast division proteins studied in our laboratory (all nuclear-encoded):
FtsZ1 and FtsZ2: Tubulin-like proteins related to bacterial FtsZ, a filament-forming GTPase that forms a ring at the midcell during bacterial cytokinesis. In plants, FtsZ1 and FtsZ2 colocalize to rings at the chloroplast division site inside the chloroplast stroma (Fig. 2). Mutations in the corresponding genes cause severe defects in chloroplast division (Fig. 3).
Figure 2. Immunofluorescence detection of FtsZ1 at the chloroplast division site. Bright-field image shown on left. FtsZ2 shows the same localization pattern. |
Figure 3. Single leaf cells showing chloroplasts in wild–type Arabidopsis plants and plants expressing FtsZ1 or FtsZ2 antisense transgenes. |
ARC6: A protein related to the cyanobacterial cell division protein Ftn2 and bearing a motif found in the DnaJ cochaperone partners of HSP70s. ARC6 is localized to the chloroplast division site in the inner envelope membrane. arc6 mutants have fragmented FtsZ1 and FtsZ2 filaments (Fig. 4) and severe chloroplast division defects.
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Figure 4. Immunofluore-scence labeling of FtsZ in the single large chloroplast of a cell from an arc6 mutant. |
Figure 5. Probable topology of ARC6 based on biochemical analysis. |
MinD: Mediates positioning of the chloroplast division site by restricting the site of FtsZ ring assembly to the middle of the organelle. This is similar to the role of MinD in bacteria. Chloroplasts in MinD mutants in have multiple FtsZ rings and misplaced or multiple constrictions.
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ARC5/DRP5B*: A member of the dynamin family of large GTPases, which function in various vesicle-budding and membrane-remodeling processes in eukaryotes. Mutations in DRP5B exhibit enlarged, dumbbell-shaped chloroplasts. The protein is localized at the division site on the cytosolic surface of the outer envelope, and has no obvious homologues in bacteria, indicating it is eukaryotic in origin. *ARC5 was renamed DPR5B base on Hong et al. 2003, Plant Mol. Biol. 53: 261-265 |
Figure 6. Dumbbell-shaped chloroplasts in arc5/drp5B mutant. |
Selected Recent Publications
McAndrew, R.S., B.J.S.C. Olson, C.L. Chi-Ham, S. Vitha, J.E. Froehlich and K.W. Osteryoung. 2008. In vivo quantitative relationship between plastid division proteins FtsZ1 and FtsZ2 and identification of ARC6 and ARC3 in a native FtsZ complex. Biochem. J., in press.
Glynn, J. M., S. Miyagishima and K.W. Osteryoung. 2007. Structure and dynamics of the chloroplast division complex. Traffic 8: 451-461.
Yoder, D.W., D. Kadirjan-Kalbach, B.J.S.C. Olson, S. Miyagishima, S.L. DeBlasio, R.P. Hangarter and K.W. Osteryoung. 2007. Effects of mutations in Arabidopsis FtsZ1 on plastid division, FtsZ ring formation and positioning, and FtsZ filament morphology in vivo. Plant Cell Physiol. 48: 775–791.
Miyagishima, S., J.E. Froehlich, and K.W. Osteryoung. 2006. PDV1 and PDV2 mediate recruitment of the dynamin-related protein ARC5 to the plastid division site. Plant Cell 18: 2506-2516.
Gao, H., T.L. Sage and K.W. Osteryoung. 2006. FZL, an FZO-like protein in plants, is a determinant of thylakoid and chloroplast morphology. Proc. Natl. Acad. Sci. USA.103: 6759-6764.
Miyagishima, S., C.P. Wolk and K.W. Osteryoung. 2005. Identification of cyanobacterial cell division genes by comparative and mutational analyses. Mol. Microbiol. 56: 126-143.
Osteryoung, K.W. and Nunnari, J. 2003. The division of endosymbiotic organelles. Science 302: 1698-1704.
Vitha, S., Froehlich, J.E., O. Koksharova, K.A. Pyke, H. van Erp and K.W.Osteryoung. 2003. ARC6 is a J-domain plastid division protein and evolutionary descendant of the cyanobacterial cell division protein Ftn2. Plant Cell 15: 1918-1933
Gao, H., D. Kadirjan-Kalbach, J.E. Froehlich and K.W. Osteryoung. 2003. ARC5, a cytosolic dynamin-like protein from plants, is part of the chloroplast division machinery. Proc. Natl. Acad. Sci. USA, 100: 4328–4333.
C.G. Wilkerson, W.K. Ray, R.S. McAndrew, K.W. Osteryoung, D.A. Gage and B.S. Phinney. 2003. Proteomic study of the Arabidopsis thalianaJ. Proteome Res., 2: 42-425.
Stokes, K.D., and K.W. Osteryoung, 2003. Early evolutionary divergence of the FtsZ1 and FtsZ2 plastid division gene families in photosynthetic eukaryotes. Gene 320: 97-108.
Osteryoung, K.W. and R.S. McAndrew. 2001. The plastid division machine. Annu. Rev. Plant Physiol. Plant Mol. Biol. 52: 315-333.
Vitha, S., R.S. McAndrew and K.W. Osteryoung. 2001. FtsZ ring formation at the chloroplast division site in plants. J. Cell Biol. 153: 111-119.
McAndrew, R.S., J.E. Froehlich, S. Vitha, K.D. Stokes and K.W. Osteryoung. 2001. Colocalization of plastid division proteins to the chloroplast stromal compartment establishes a new functional relationship between FtsZ1 and FtsZ2 in higher plants. Plant Physiol. 127: 1656-1666.
Colletti, K.S., E.A. Tattersall, K.A. Pyke, J.E.Froelich, K.D.Stokes, and K.W Osteryoung. 2000. A homologue of the bacterial cell division site-determining factor MinD mediates placement of the chloroplast division apparatus. Curr. Biol. 10: 507-16.
Osteryoung, K.W., K.D. Stokes, S.M. Rutherford, A.L. Percival and W.Y. Lee. 1998. Chloroplast division in higher plants requires members of two functionally divergent FtsZ gene families. Plant Cell 10: 1991-2004.
Osteryoung, K.W. and E. Vierling. 1995. Conserved cell and organelle division. Nature 376: 473-474.
National Science Foundation, MCB-0544676, Towards a Model for FtsZ Structure and Dynamics in Chloroplast Division, K.W. Osteryoung, PI, 7/1/06-6/30/10.
US Department of Energy. Functional Analysis of ARC6 and Ftn2, Orthologous Regulators of Chloroplast and Cyanobacterial Cell Division, K.W. Osteryoung, PI, 8/1/06-7/31/09.
National Science Foundation, Arabidopsis 2010: Understanding Chloroplast Function, PI R. Last; co-PIs K. Osteryoung, C. Benning, D. DellaPenna, J. Ohlrogge, Y. Shachar-Hill, A. Weber, W. Wedemeyer. 12/01/05- 11/30/09.
National Science Foundation ” Arabidopsis 2010: Identification of New Plastid Division Genes in Arabidopsis and Comprehensive Analysis of Their Functions,” K.W.Osteryoung, PI, 9/1/03-8/31/07.
Introductory Biology: Cells and Molecules, MSU (Biological Sciences 111, undergraduate lecture, ~450 students, 3 credits).
June 2008, left to right:
Jon Glynn, graduate student (Genetics)
Deena Kadirjan-Kalbach, lab manager
Kathy Osteryoung, PI
Roshan Shrestha, postdoc
Not shown:
John Sherbeck, undergraduate researcher
Fiqa Ahmad Hisham, lab helper
