Changes in Root Cap pH Are Required for the Gravity Response of the Arabidopsis Root

Although the columella cells of the root cap have been identified as the site of gravity perception, the cellular events that mediate gravity signaling remain poorly understood. To determine if cytoplasmic and/or wall pH mediates the initial stages of root gravitropism, we combined a novel cell wall...

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Bibliographic Details
Published in:The Plant cell 2001-04, Vol.13 (4), p.907-921
Main Authors: Fasano, Jeremiah M., Swanson, Sarah J., Blancaflor, Elison B., Dowd, Peter E., Kao, Teh-hui, Gilroy, Simon
Format: Article
Language:English
Subjects:
Arabidopsis - growth & development
Arabidopsis - physiology
Cell growth
Cell Wall - physiology
Cell walls
Cellulose
Dextrans
Fluoresceins
Fluorescent Dyes
Gravitropism
Gravity Sensing
Hydrogen-Ion Concentration
Kinetics
Life Sciences (General)
Meristem - growth & development
Meristem - physiology
Microscopes
Microscopy, Confocal
pH sensors
Plant roots
Plant Roots - growth & development
Plant Roots - physiology
Plants
Protons
Root cap
Space life sciences
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Summary:Although the columella cells of the root cap have been identified as the site of gravity perception, the cellular events that mediate gravity signaling remain poorly understood. To determine if cytoplasmic and/or wall pH mediates the initial stages of root gravitropism, we combined a novel cell wall pH sensor (a cellulose binding domain peptide-Oregon green conjugate) and a cytoplasmic pH sensor (plants expressing pH-sensitive green fluorescent protein) to monitor pH dynamics throughout the graviresponding Arabidopsis root. The root cap apoplast acidified from pH 5.5 to 4.5 within 2 min of gravistimulation. Concomitantly, cytoplasmic pH increased in columella cells from 7.2 to 7.6 but was unchanged elsewhere in the root. These changes in cap pH preceded detectable tropic growth or growth-related pH changes in the elongation zone cell wall by 10 min. Altering the gravity-related columella cytoplasmic pH shift with caged protons delayed the gravitropic response. Together, these results suggest that alterations in root cap pH likely are involved in the initial events that mediate root gravity perception or signal transduction.
ISSN:1040-4651
1532-298X
DOI:10.1105/tpc.13.4.907