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.

Regulation of organ straightening and plant posture by an actin–myosin XI cytoskeleton


An Erratum to this article was published on 14 April 2015


Plants are able to bend nearly every organ in response to environmental stimuli such as gravity and light1,2. After this first phase, the responses to stimuli are restrained by an independent mechanism, or even reversed, so that the organ will stop bending and attain its desired posture. This phenomenon of organ straightening has been called autotropism3 and autostraightening4 and modelled as proprioception5. However, the machinery that drives organ straightening and where it occurs are mostly unknown. Here, we show that the straightening of inflorescence stems is regulated by an actin–myosin XI cytoskeleton in specialized immature fibre cells that are parallel to the stem and encircle it in a thin band. Arabidopsis mutants defective in myosin XI (specifically XIf and XIk) or ACTIN8 exhibit hyperbending of stems in response to gravity, an effect independent of the physical properties of the shoots. The actin–myosin XI cytoskeleton enables organs to attain their new position more rapidly than would an oscillating series of diminishing overshoots in environmental stimuli. We propose that the long actin filaments in elongating fibre cells act as a bending tensile sensor to perceive the organ's posture and trigger the straightening system.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Deficiency of myosins XIf and XIk enhances organ bending in response to gravity and light stimuli.
Figure 2: Myosins XIf and XIk are required for straightening of inflorescence stems.
Figure 3: Fibre cells expressing myosins XIf and XIk play a role in straightening.
Figure 4: Fibre cells develop extremely long actin cables and a defect in ACTIN8 causes abnormal phenotypes similar to those of myosin xif xik.


  1. 1

    Darwin, C. The Power of Movements in Plants (John Murray, 1880).

    Book  Google Scholar 

  2. 2

    Gilroy, S. & Masson, P. H. Plant Tropisms (Blackwell, 2008).

    Google Scholar 

  3. 3

    Stankovic, B., Volkmann, D. & Sack, F. D. Autotropism, automorphogenesis, and gravity. Physiol. Plant. 102, 328–335 (1998).

    CAS  Article  Google Scholar 

  4. 4

    Iino, M. Toward understanding the ecological functions of tropisms: interactions among and effects of light on tropisms. Curr. Opin. Plant Biol. 9, 89–93 (2006).

    Article  Google Scholar 

  5. 5

    Bastien, R., Bohr, T., Moulia, B. & Douady, S. Unifying model of shoot gravitropism reveals proprioception as a central feature of posture control in plants. Proc. Natl Acad. Sci. USA 110, 755–760 (2013).

    CAS  Article  Google Scholar 

  6. 6

    Shimmen, T. & Yokota, E. Cytoplasmic streaming in plants. Curr. Opin. Cell Biol. 16, 68–72 (2004).

    CAS  Article  Google Scholar 

  7. 7

    Tominaga, M. & Nakano, A. Plant-specific myosin XI, a molecular perspective. Front. Plant Sci. 3, 211 (2012).

    Article  Google Scholar 

  8. 8

    Ueda, H. et al. Myosin-dependent endoplasmic reticulum motility and F-actin organization in plant cells. Proc. Natl Acad. Sci. USA 107, 6894–6899 (2010).

    CAS  Article  Google Scholar 

  9. 9

    Peremyslov, V. V., Prokhnevsky, A. I. & Dolja, V. V. Class XI myosins are required for development, cell expansion, and F-Actin organization in Arabidopsis. Plant Cell 22, 1883–1897 (2010).

    CAS  Article  Google Scholar 

  10. 10

    Sparkes, I. A. Motoring around the plant cell: insights from plant myosins. Biochem. Soc. Trans. 38, 833–838 (2010).

    CAS  Article  Google Scholar 

  11. 11

    Avisar, D., Abu-Abied, M., Belausov, E. & Sadot, E. Myosin XIK is a major player in cytoplasm dynamics and is regulated by two amino acids in its tail. J. Exp. Bot. 63, 241–249 (2012).

    CAS  Article  Google Scholar 

  12. 12

    Tamura, K. et al. Myosin XI-i links the nuclear membrane to the cytoskeleton to control nuclear movement and shape in Arabidopsis. Curr. Biol. 23, 1776–1781 (2013).

    CAS  Article  Google Scholar 

  13. 13

    Esmon, C. A. et al. A gradient of auxin and auxin-dependent transcription precedes tropic growth responses. Proc. Natl Acad. Sci. USA 103, 236–241 (2006).

    CAS  Article  Google Scholar 

  14. 14

    Haga, K. & Iino, M. Asymmetric distribution of auxin correlates with gravitropism and phototropism but not with autostraightening (autotropism) in pea epicotyls. J. Exp. Bot. 57, 837–847 (2006).

    CAS  Article  Google Scholar 

  15. 15

    Cai, C., Henty-Ridilla, J. L., Szymanski, D. B. & Staiger, C. J. Arabidopsis myosin XI: a motor rules the tracks. Plant Physiol. (2014).

  16. 16

    Vidali, L. et al. Myosin XI is essential for tip growth in Physcomitrella patens. Plant Cell 22, 1868–1882 (2010).

    CAS  Article  Google Scholar 

  17. 17

    Kandasamy, M. K., McKinney, E. C. & Meagher, R. B. A single vegetative actin isovariant overexpressed under the control of multiple regulatory sequences is sufficient for normal Arabidopsis development. Plant Cell 21, 701–718 (2009).

    CAS  Article  Google Scholar 

  18. 18

    Lanza, M. et al. Role of actin cytoskeleton in brassinosteroid signaling and in its integration with the auxin response in plants. Dev. Cell 22, 1275–1285 (2012).

    CAS  Article  Google Scholar 

  19. 19

    Kato, T., Morita, M. T. & Tasaka, M. Defects in dynamics and functions of actin filament in Arabidopsis caused by the dominant-negative actin fiz1-induced fragmentation of actin filament. Plant Cell Physiol. 51, 333–338 (2010).

    CAS  Article  Google Scholar 

  20. 20

    Nakamura, M., Toyota, M., Tasaka, M. & Morita, M. T. An Arabidopsis E3 ligase, SHOOT GRAVITROPISM9, modulates the interaction between statoliths and F-actin in gravity sensing. Plant Cell 23, 1830–1848 (2011).

    CAS  Article  Google Scholar 

  21. 21

    Blancaflor, E. B. Regulation of plant gravity sensing and signaling by the actin cytoskeleton. Am. J. Bot. 100, 143–152 (2013).

    CAS  Article  Google Scholar 

  22. 22

    Fukaki, H. et al. Genetic evidence that the endodermis is essential for shoot gravitropism in Arabidopsis thaliana. Plant J. 14, 425–430 (1998).

    CAS  Article  Google Scholar 

  23. 23

    Hashiguchi, Y., Tasaka, M. & Morita, M. T. Mechanism of higher plant gravity sensing. Am. J. Bot. 100, 91–100 (2013).

    CAS  Article  Google Scholar 

  24. 24

    Blancaflor, E. B., Fasano, J. M. & Gilroy, S. Mapping the functional roles of cap cells in the response of Arabidopsis primary roots to gravity. Plant Physiol. 116, 213–222 (1998).

    CAS  Article  Google Scholar 

  25. 25

    Hou, G., Mohamalawari, D. R. & Blancaflor, E. B. Enhanced gravitropism of roots with a disrupted cap actin cytoskeleton. Plant Physiol. 131, 1360–1373 (2003).

    CAS  Article  Google Scholar 

  26. 26

    Yamamoto, K. & Kiss, J. Z. Disruption of the actin cytoskeleton results in the promotion of gravitropism in inflorescence stems and hypocotyls of Arabidopsis. Plant Physiol. 128, 669–681 (2002).

    CAS  Article  Google Scholar 

  27. 27

    Palmieri, M. & Kiss, J. Z. Disruption of the F-actin cytoskeleton limits statolith movement in Arabidopsis hypocotyls. J. Exp. Bot. 56, 2539–2550 (2005).

    CAS  Article  Google Scholar 

  28. 28

    Hou, G. et al. The promotion of gravitropism in Arabidopsis roots upon actin disruption is coupled with the extended alkalinization of the columella cytoplasm and a persistent lateral auxin gradient. Plant J. 39, 113–125 (2004).

    CAS  Article  Google Scholar 

  29. 29

    Nakashima, J., Liao, F., Sparks, J. A., Tang, Y. & Blancaflor, E. B. The actin cytoskeleton is a suppressor of the endogenous skewing behaviour of Arabidopsis primary roots in microgravity. Plant Biol. (Stuttg.) 16(suppl. 1), 142–150 (2014).

    Article  Google Scholar 

  30. 30

    Nakagawa, Y. et al. Arabidopsis plasma membrane protein crucial for Ca2+ influx and touch sensing in roots. Proc. Natl Acad. Sci. USA 104, 3639–3644 (2007).

    CAS  Article  Google Scholar 

  31. 31

    Yamanaka, T. et al. MCA1 and MCA2 that mediate Ca2+ uptake have distinct and overlapping roles in Arabidopsis. Plant Physiol. 152, 1284–1296 (2010).

    CAS  Article  Google Scholar 

  32. 32

    Hayakawa, K., Tatsumi, H. & Sokabe, M. Actin stress fibers transmit and focus force to activate mechanosensitive channels. J. Cell Sci. 121, 496–503 (2008).

    CAS  Article  Google Scholar 

  33. 33

    Peremyslov, V. V., Prokhnevsky, A. I., Avisar, D. & Dolja, V. V. Two class XI myosins function in organelle trafficking and root hair development in Arabidopsis. Plant Physiol. 146, 1109–1116 (2008).

    CAS  Article  Google Scholar 

  34. 34

    Nelson, B. K., Cai, X. & Nebenführ, A. A multicolored set of in vivo organelle markers for co-localization studies in Arabidopsis and other plants. Plant J. 51, 1126–1136 (2007).

    CAS  Article  Google Scholar 

  35. 35

    Saito, C., Morita, M. T., Kato, T. & Tasaka, M. Amyloplasts and vacuolar membrane dynamics in the living graviperceptive cell of the Arabidopsis inflorescence stem. Plant Cell 17, 548–558 (2005).

    CAS  Article  Google Scholar 

  36. 36

    Ye, Z. H., Freshour, G., Hahn, M. G., Burk, D. H. & Zhong, R. Vascular development in Arabidopsis. Int. Rev. Cytol. 220, 225–256 (2002).

    CAS  Article  Google Scholar 

Download references


We are grateful to Tobias Baskin (University of Massachusetts), Alistair M. Hetherington (University of Bristol) and James Raymond (Eigoken) for critical readings of this manuscript and to Moritoshi Iino (Osaka City University), Tomomi Suzuki (Kyoto University) and Akira Nagatani (Kyoto University) for helpful discussion. We are also grateful to Shoko Hongo (Tohoku University), Kazuhiko Nishitani (Tohoku University), Masatsugu Toyota (NAIST) and Masatoshi Taniguchi (NAIST) for their technical support; to Valerian V. Dolja (Oregon State University) for his donation of the ProXIk:XIk–YFP construct, transgenic seeds and anti-XIk antibody; to Takashi Ueda (University of Tokyo) for his donation of the Pro35S:Lifeact–Venus construct; to Tsuyoshi Nakagawa (Shimane University) for his donation of Gateway vectors; and to the ABRC for providing seeds of A. thaliana tDNA insertion mutants. This work was supported by Specially Promoted Research of Grant-in-Aid for Scientific Research to I.H-N. (no. 22000014), Grants-in-Aid for Scientific Research to K.O. (no. 23.2) and to H.U. (nos. 21200065 and 25440132) from the Japan Society for the Promotion of Science (JSPS).

Author information




K.O., H.U., T.S. and I.H-N. conceived the study; K.O. and H.U. designed the experiments; K.O. generated myosin mutants and analysed tropic responses. K.O. and H.U. generated transgenic plants and analysed straightening; K.O., T.K., M.T. and M.T.M. analysed gravitropic responses; K.O., H.U., T.S., K.T. and I.H-N. participated in discussion; K.O., H.U., T.S. and I.H-N. wrote the manuscript.

Corresponding author

Correspondence to Ikuko Hara-Nishimura.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Okamoto, K., Ueda, H., Shimada, T. et al. Regulation of organ straightening and plant posture by an actin–myosin XI cytoskeleton. Nature Plants 1, 15031 (2015).

Download citation

Further reading


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