, Volume 201, Issue 1–2, pp 92–100 | Cite as

Mechanotransduction molecules in the plant gravisensory response: Amyloplast/statolith membranes contain a β1 integrin-like protein

  • Timothy M. Lynch
  • Philip M. Lintilhac
  • David Domozych


It has been hypothesized that the sedimentation of amyloplasts within root cap cells is the primary event in the plant gravisensory-signal transduction cascade. Statolith sedimentation, with its ability to generate weighty mechanical signals, is a legitimate means for organisms to discriminate the direction of the gravity vector. However, it has been demonstrated that starchless mutants with reduced statolith densities maintain some ability to sense gravity, calling into question the statolith sedimentation hypothesis. Here we report on the presence of a β1 integrin-like protein localized inside amyloplasts of tobacco NT-1 suspension culture, callus cells, and whole-root caps. Two different antibodies to the β1 integrin, one to the cytoplasmic domain and one to the extracellular domain, localize in the vicinity of the starch grains within amyloplasts of NT-1. Biochemical data reveals a 110-kDa protein immunoprecipitated from membrane fractions of NT-1 suspension culture indicating size homology to known β1 integrin in animals. This study provides the first direct evidence for the possibility of integrin-mediated signal transduction in the perception of gravity by higher plants. An integrin-mediated pathway, initiated by starch grain sedimentation within the amyloplast, may provide the signal amplification necessary to explain the gravitropic response in starch-depleted cultivars.


Amyloplast Gravity Integrin Mechanotransduction Statolith Tobacco 





ethyl alcohol


liquid propane


London Resin


phosphate-buffered saline with Tween


transmission electron microscopy


optical-sectioning microscopy


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Copyright information

© Springer-Verlag 1998

Authors and Affiliations

  • Timothy M. Lynch
    • 1
  • Philip M. Lintilhac
    • 1
  • David Domozych
    • 2
  1. 1.Botany DepartmentUniversity of VermontBurlingtonUSA
  2. 2.Department of BiologySkidmore CollegeSaratoga Springs

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