Journal Article

The Role of Wall Ca<sup>2+</sup> in the Regulation of Wall Extensibility During the Acid-induced Extension of Soybean Hypocotyl Cell Walls

Naofumi Ezaki, Nobuo Kido, Koji Takahashi and Kiyoshi Katou

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 11, pages 1831-1838
Published in print November 2005 | ISSN: 0032-0781
Published online November 2005 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pci199
The Role of Wall Ca2+ in the Regulation of Wall Extensibility During the Acid-induced Extension of Soybean Hypocotyl Cell Walls

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We examined the acid-facilitated yielding properties of cell walls of soybean hypocotyls and the effects of Ca2+ upon the properties by stress–strain analyses using glycerinated hollow cylinders (GHCs) from the elongating regions of the hypocotyls. Stress–extension rate curves of native GHCs showed characteristic changes with pH, all indicating the existence of yield threshold tension (y) as well as wall extensibility (ϕ), i.e. a downward shift of y and an increase in ϕ with wall acidification. The acid-induced downward shift of y was inhibited by boiling of GHCs. In contrast, a considerable increase in ϕ with acidification remained even after boiling. This indicates that ϕ consists of two components, i.e. heat-sensitive and heat-resistant, both being pH sensitive. A Ca2+ chelator (Quin 2) dramatically increased ϕ at a neutral pH. Subsequent addition of Ca2+ or ruthenium red suppressed the chelator-induced increase in ϕ. These findings suggest that wall Ca2+ plays an important role in the regulation of wall extensibility during the acid-induced wall extension by reacting with carboxyl groups of wall pectin.

Keywords: Glycine max; Pectin; Stress–strain properties; Wall Ca2+; Wall extension; EGTA, ethylene glycol bis (β-aminoethylether)-N,N,N′,N′-tetraacetic acid; GHC, glycerinated hollow cylinder of hypocotyl segment; Φ, wall extensibility in vivo; ϕ, wall extensibility in vitro; Quin 2, 8-amino-2-[(2-amino-5-methylphenoxy)methyl]-6-methoxyquinoline-N,N,N′,N′-tetraacetic acid; RR, ruthenium red; Y, yield threshold pressure; y, yield threshold tension

Journal Article.  5430 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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