Journal Article

Mechanosensitive Ca<sup>2+</sup> Release from Intracellular Stores in <i>Nitella flexilis</i>

Munehiro Kikuyama and Masashi Tazawa

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 42, issue 4, pages 358-365
Published in print April 2001 | ISSN: 0032-0781
Published online April 2001 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pce043
Mechanosensitive Ca2+ Release from Intracellular Stores in Nitella flexilis

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We found previously that the cytoplasmic drop isolated from internodal cells of Nitella flexilis releases Ca2+ in response to hypotonic treatment and named the phenomenon hydration-induced Ca2+ release (HICR). The HICR is assumed to be a result of activation of Ca2+ permeable channels in the membrane of Ca2+ stores in a stretch-activated manner. To prove this idea, mechanical stimulus was applied to the drop by means of shooting isotonic/hypnotic medium or silicon oil into the drop, or compressing the drop. All these mechanical stimuli induced a rapid increase in the Ca2+ concentration of the drop. The chloroplast fraction isolated from the cytoplasmic drop released Ca2+ on compression, while the chloroplast-free cytoplasm did not. In Chara corallina, the cytoplasmic drop, which shows a very weak HICR, also responded weakly to the mechanical stimulus, but the chloroplast fraction was inert. When chloroplasts from Chara were added to the chloroplast-free cytoplasm of N. flexilis, the cytoplasm recovered the mechanoresponse. Starch grains were as effective as chloroplasts. The data indicate that Ca2+ permeable channels in the membrane of Ca2+ stores in N. flexilis are really mechano-sensitive.

Keywords: Key words: Aequorin — Ca2+ store — Chloroplast — Hydration induced Ca2+ release (HICR) — Nitella flexilis — Mechanosensitive ion channel.; Abbreviations: ER, endoplasmic reticulum; EGTA, ethyleneglycol bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid; Δ[Ca2+], increase in Ca2+ concentration; HICR, hydration-induced calcium release; Osm, osmolar; PM, photomultiplier.

Journal Article.  4389 words.  Illustrated.

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

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