First published online January 9, 2003; 10.1104/pp.011841
Plant Physiol, February 2003, Vol. 131, pp. 536-546
A no hydrotropic response Root Mutant that Responds
Positively to Gravitropism in Arabidopsis1,[w]
Delfeena
Eapen,2
María Luisa
Barroso,2
María Eugenia
Campos,
Georgina
Ponce,
Gabriel
Corkidi,
Joseph G.
Dubrovsky, and
Gladys I.
Cassab*
Departamento de Biología Molecular de Plantas, Instituto de
Biotecnología, Universidad Nacional Autónoma de
México, Apartado Postal 510-3, Cuernavaca, Morelos, 62250 Mexico (D.E., M.L.B., M.E.C., G.P., J.G.D., G.I.C.); and Laboratorio de
Imágenes y Visión, Centro de Ciencias Aplicadas y
Desarrollo Tecnológico, Universidad Nacional Autónoma de
México, México, D.F., 04510 Mexico (G.C.)
For most plants survival depends upon the capacity of root
tips to sense and move towards water and other nutrients in the soil.
Because land plants cannot escape environmental stress they use
developmental solutions to remodel themselves in order to better adapt
to the new conditions. The primary site for perception of underground
signals is the root cap (RC). Plant roots have positive hydrotropic
response and modify their growth direction in search of water. Using a
screening system with a water potential gradient, we isolated a
no hydrotropic response (nhr)
semi-dominant mutant of Arabidopsis that continued to grow downwardly
into the medium with the lowest water potential contrary to the
positive hydrotropic and negative gravitropic response seen in wild
type-roots. The lack of hydrotropic response of nhr1
roots was confirmed in a system with a gradient in air moisture. The
root gravitropic response of nhr1 seedlings was
significantly faster in comparison with those of wild type. The
frequency of the waving pattern in nhr1 roots was
increased compared to those of wild type. nhr1 seedlings
had abnormal root cap morphogenesis and reduced root growth sensitivity
to abscisic acid (ABA) and the polar auxin transport inhibitor
N-(1-naphtyl)phtalamic acid (NPA). These results showed that
hydrotropism is amenable to genetic analysis and that an ABA signaling
pathway participates in sensing water potential gradients through the
root cap.
1
This research was supported by the Mexican
Council for Science and Technology (grant nos. CONACYT 25186N and
36071N), by the Universidad Nacional Autónoma de México
(Dirección General de Asuntos del Personal
Académico grant no. IN208999), by University of California
(Mexus), and by DeGAPA IN204496 (scholarships to M.L.B. and D.E.).
2
These authors contributed equally to the paper.
*
Corresponding author: e-mail gladys{at}ibt.unam.mx; fax
52-77-73-13 9988.
[w]
The online version of this article contains Web-only
data. The supplemental material is available at
www.plantphysiol.org.
© 2003 American Society of Plant Biologists
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