Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Structural insights into yeast septin organization from polarized fluorescence microscopy


Septins are polymerizing GTPases1 that function in cortical organization and cell division2,3,4. In Saccharomyces cerevisiae they localize at the isthmus between the mother and the daughter cells, where they undergo a transition from a non-dynamic hourglass-shaped assembly5 to two separate rings, at the onset of cytokinesis6,7. Septins form filaments as pure protein8 and in vivo9, but the filament organization within the hourglass and ring structures is controversial9,10. Here, we use polarized fluorescence microscopy11 of orientationally constrained green fluorescent protein to determine septin filament organization and dynamics in living yeast. We found that the hourglass is made of filaments aligned along the yeast bud neck. During the transition from hourglass to rings the filaments rotate through 90° in the membrane plane and become circumferential. These data resolve a long-standing controversy in the field and provide strong evidence that septins have a mechanical function in cell division.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: The experimental system.
Figure 2: The average dipole direction.
Figure 3: The average filament direction.


  1. Field, C. M. et al. A purified Drosophila septin complex forms filaments and exhibits GTPase activity. J. Cell Biol. 133, 605–616 (1996)

    CAS  Article  Google Scholar 

  2. Kinoshita, M. et al. Nedd5, a mammalian septin, is a novel cytoskeletal component interacting with actin-based structures. Genes Dev. 11, 1535–1547 (1997)

    CAS  Article  Google Scholar 

  3. Neufeld, T. P. & Rubin, G. M. The Drosophila peanut gene is required for cytokinesis and encodes a protein similar to yeast putative bud neck filament proteins. Cell 77, 371–379 (1994)

    CAS  Article  Google Scholar 

  4. Hartwell, L. H. Genetic control of the cell division cycle in yeast. IV. Genes controlling bud emergence and cytokinesis. Exp. Cell Res. 69, 265–276 (1971)

    CAS  Article  Google Scholar 

  5. Dobbelaere, J. & Barral, Y. Spatial coordination of cytokinetic events by compartmentalization of the cell cortex. Science 305, 393–396 (2004)

    ADS  CAS  Article  Google Scholar 

  6. Lippincott, J., Shannon, K. B., Shou, W., Deshaies, R. J. & Li, R. The Tem1 small GTPase controls actomyosin and septin dynamics during cytokinesis. J. Cell Sci. 114, 1379–1386 (2001)

    CAS  PubMed  Google Scholar 

  7. Cid, V. J., Adamikova, L., Sanchez, M., Molina, M. & Nombela, C. Cell cycle control of septin ring dynamics in the budding yeast. Microbiology 147, 1437–1450 (2001)

    CAS  Article  Google Scholar 

  8. Frazier, J. A. et al. Polymerization of purified yeast septins: evidence that organized filament arrays may not be required for septin function. J. Cell Biol. 143, 737–749 (1998)

    CAS  Article  Google Scholar 

  9. Rodal, A. A., Kozubowski, L., Goode, B. L., Drubin, D. G. & Hartwig, J. H. Actin and septin ultrastructures at the budding yeast cell cortex. Mol. Biol. Cell 16, 372–384 (2005)

    CAS  Article  Google Scholar 

  10. Byers, B. & Goetsch, L. A highly ordered ring of membrane-associated filaments in budding yeast. J. Cell Biol. 69, 717–721 (1976)

    CAS  Article  Google Scholar 

  11. Axelrod, D. Fluorescence polarization microscopy. Methods Cell Biol. 30, 333–352 (1989)

    CAS  Article  Google Scholar 

  12. Sheff, M. A. & Thorn, K. S. Optimized cassettes for fluorescent protein tagging in Saccharomyces cerevisiae. Yeast 21, 661–670 (2004)

    CAS  Article  Google Scholar 

  13. Burghardt, T. P. Model-independent fluorescence polarization for measuring order in a biological assembly. Biopolymers 23, 2383–2406 (1984)

    CAS  Article  Google Scholar 

  14. Dale, R. E. et al. Model-independent analysis of the orientation of fluorescent probes with restricted mobility in muscle fibers. Biophys. J. 76, 1606–1618 (1999)

    ADS  CAS  Article  Google Scholar 

  15. Desper, C. R. & Kimura, I. Mathematics of the polarized-fluorescence experiment. J. Appl. Phys. 38, 4225–4233 (1967)

    ADS  CAS  Article  Google Scholar 

  16. Inoue, S., Shimomura, O., Goda, M., Shribak, M. & Tran, P. T. Fluorescence polarization of green fluorescence protein. Proc. Natl Acad. Sci. USA 99, 4272–4277 (2002)

    ADS  CAS  Article  Google Scholar 

  17. Axelrod, D. Carbocyanine dye orientation in red cell membrane studied by microscopic fluorescence polarization. Biophys. J. 26, 557–573 (1979)

    ADS  CAS  Article  Google Scholar 

  18. Volkmer, A., Subramaniam, V., Birch, D. J. & Jovin, T. M. One- and two-photon excited fluorescence lifetimes and anisotropy decays of green fluorescent proteins. Biophys. J. 78, 1589–1598 (2000)

    CAS  Article  Google Scholar 

  19. Corrie, J. E. et al. Dynamic measurement of myosin light-chain-domain tilt and twist in muscle contraction. Nature 400, 425–430 (1999)

    ADS  CAS  Article  Google Scholar 

  20. Rocheleau, J. V., Edidin, M. & Piston, D. W. Intrasequence GFP in class I MHC molecules, a rigid probe for fluorescence anisotropy measurements of the membrane environment. Biophys. J. 84, 4078–4086 (2003)

    CAS  Article  Google Scholar 

  21. Lupas, A., Van Dyke, M. & Stock, J. Predicting coiled coils from protein sequences. Science 252, 1162–1164 (1991)

    ADS  CAS  Article  Google Scholar 

  22. Yang, F., Moss, L. G. & Phillips, G. N. Jr. The molecular structure of green fluorescent protein. Nature Biotechnol. 14, 1246–1251 (1996)

    CAS  Article  Google Scholar 

  23. Ormo, M. et al. Crystal structure of the Aequorea victoria green fluorescent protein. Science 273, 1392–1395 (1996)

    ADS  CAS  Article  Google Scholar 

  24. Li, X. et al. Deletions of the Aequorea victoria green fluorescent protein define the minimal domain required for fluorescence. J. Biol. Chem. 272, 28545–28549 (1997)

    CAS  Article  Google Scholar 

  25. Dobbelaere, J., Gentry, M. S., Hallberg, R. L. & Barral, Y. Phosphorylation-dependent regulation of septin dynamics during the cell cycle. Dev. Cell 4, 345–357 (2003)

    CAS  Article  Google Scholar 

  26. Caviston, J. P., Longtine, M., Pringle, J. R. & Bi, E. The role of Cdc42p GTPase-activating proteins in assembly of the septin ring in yeast. Mol. Biol. Cell 14, 4051–4066 (2003)

    CAS  Article  Google Scholar 

  27. Schmidt, M., Bowers, B., Varma, A., Roh, D. H. & Cabib, E. In budding yeast, contraction of the actomyosin ring and formation of the primary septum at cytokinesis depend on each other. J. Cell Sci. 115, 293–302 (2002)

    CAS  PubMed  Google Scholar 

  28. Picart, C. & Discher, D. E. Actin protofilament orientation at the erythrocyte membrane. Biophys. J. 77, 865–878 (1999)

    ADS  CAS  Article  Google Scholar 

  29. Tatchell, K. & Robinson, L. C. Use of green fluorescent protein in living yeast cells. Methods Enzymol. 351, 661–683 (2002)

    CAS  Article  Google Scholar 

Download references


We thank I. Vrabioiu and colleagues at INCDMF-CEFIN, Romania, for designing and fabricating the rotating stage used for our experiments, and M. Volles for comments. This work was supported by a National Institutes of Health grant to T.J.M.

Author information

Authors and Affiliations


Corresponding author

Correspondence to Alina M. Vrabioiu.

Ethics declarations

Competing interests

Reprints and permissions information is available at The authors declare no competing financial interests.

Supplementary information

Supplementary Notes

This file contains Supplementary Methods, Supplementary Discussion, Supplementary Notes, Supplementary Tables, Supplementary Figures and Supplementary Movie Legend. (DOC 1163 kb)

Supplementary Figure 1

Characterization of the Cdc12 strain. (JPG 24 kb)

Supplementary Figure 2

Hourglass area C quantitations. (JPG 17 kb)

Supplementary Figure 3

Cdc3 strain rearrangement time lapse. (JPG 22 kb)

Supplementary Movie

This movie indicates that the septin filaments change orientation during the hourglass to rings transition. (MOV 4949 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Vrabioiu, A., Mitchison, T. Structural insights into yeast septin organization from polarized fluorescence microscopy. Nature 443, 466–469 (2006).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing