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Mechanotransduction molecules in the plant gravisensory response: amyloplast/statolith membranes contain a beta 1 integrin-like proteinIt 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 beta 1 integrin-like protein localized inside amyloplasts of tobacco NT-1 suspension culture, callus cells, and whole-root caps. Two different antibodies to the beta 1 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 beta 1 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.
Document ID
20040089258
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Lynch, T. M.
(University of Vermont Burlington, United States)
Lintilhac, P. M.
Domozych, D.
Date Acquired
August 21, 2013
Publication Date
January 1, 1998
Publication Information
Publication: Protoplasma
Volume: 201
Issue: 2-Jan
ISSN: 0033-183X
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: NAGW-3604
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Plant Biology
Non-NASA Center

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