This Article Full Text Full Text (PDF) All Versions of this Article: 134/2/735    most recent pp.103.031294v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via ISI Web of Science (14) Citing Articles via Google Scholar Google Scholar Articles by Yamagami, M. Articles by Iino, M. Search for Related Content PubMed PubMed Citation Articles by Yamagami, M. Articles by Iino, M. Agricola Articles by Yamagami, M. Articles by Iino, M.

DEVELOPMENT AND HORMONE ACTION

Two Distinct Signaling Pathways Participate in Auxin-Induced Swelling of Pea Epidermal Protoplasts

Institute for Environmental Science, Rokkasho-mura, Aomori 039–3212, Japan (M.Y.); Botanical Gardens, Graduate School of Science, Osaka City University, Kisaichi, Katano-shi, Osaka 576–0004, Japan (K.H., M.I.); and Horticulture Research International, Warwick CV35 9EF, United Kingdom (R.M.N.)

Protoplast swelling was used to investigate auxin signaling in the growth-limiting stem epidermis. The protoplasts of epidermal cells were isolated from elongating internodes of pea (Pisum sativum). These protoplasts swelled in response to auxin, providing the clearest evidence that the epidermis can directly perceive auxin. The swelling response to the natural auxin IAA showed a biphasic dose response curve but that to the synthetic auxin 1-naphthalene acetic acid (NAA) showed a simple bell-shaped dose response curve. The responses to IAA and NAA were further analyzed using antibodies raised against ABP1 (auxin-binding protein 1), and their dependency on extracellular ions was investigated. Two signaling pathways were resolved for IAA, an ABP1-dependent pathway and an ABP1-independent pathway that is much more sensitive to IAA than the former. The response by the ABP1 pathway was eliminated by anti-ABP1 antibodies, had a higher sensitivity to NAA, and did not depend on extracellular Ca²⁺. In contrast, the response by the non-ABP1 pathway was not affected by anti-ABP1 antibodies, had no sensitivity to NAA, and depended on extracellular Ca²⁺. The swelling by either pathway required extracellular K⁺ and Cl^–. The auxin-induced growth of pea internode segments showed similar response patterns, including the occurrence of two peaks in the dose response curve for IAA and the difference in Ca²⁺ requirements. It is suggested that two signaling pathways participate in auxin-induced internode growth and that the non-ABP1 pathway is more likely to be involved in the control of growth by constitutive concentrations of endogenous auxin.

^* Corresponding author; e-mail iino{at}sci.osaka-cu.ac.jp; fax 81–72–891–7199.

Received August 4, 2003; returned for revision September 8, 2003; accepted November 7, 2003.

This article has been cited by other articles:

				M. Christian, W. B. Hannah, H. Luthen, and A. M. Jones Identification of auxins by a chemical genomics approach J. Exp. Bot., July 1, 2008; 59(10): 2757 - 2767. [Abstract] [Full Text] [PDF]

				A. Kawabe, B. Hansson, J. Hagenblad, A. Forrest, and D. Charlesworth Centromere Locations and Associated Chromosome Rearrangements in Arabidopsis lyrata and A. thaliana Genetics, July 1, 2006; 173(3): 1613 - 1619. [Abstract] [Full Text] [PDF]

				K. Haga and M. Iino Asymmetric distribution of auxin correlates with gravitropism and phototropism but not with autostraightening (autotropism) in pea epicotyls J. Exp. Bot., March 1, 2006; 57(4): 837 - 847. [Abstract] [Full Text] [PDF]

				P. Campanoni and P. Nick Auxin-Dependent Cell Division and Cell Elongation. 1-Naphthaleneacetic Acid and 2,4-Dichlorophenoxyacetic Acid Activate Different Pathways Plant Physiology, March 1, 2005; 137(3): 939 - 948. [Abstract] [Full Text] [PDF]