Journal Article

Involvement of a Calcium-Dependent Protein Kinase in Hypoosmotic Turgor Regulation in a Brackish Water Characeae <i>Lamprothamnium succinctum</i>

Takashi Yuasa, Yoshiji Okazaki, Naohiko Iwasaki and Shoshi Muto

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 38, issue 5, pages 586-596
Published in print January 1997 | ISSN: 0032-0781
Published online January 1997 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/oxfordjournals.pcp.a029208
Involvement of a Calcium-Dependent Protein Kinase in Hypoosmotic Turgor Regulation in a Brackish Water Characeae Lamprothamnium succinctum

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Calcium ion is a key messenger in turgor regulation of internodal cells of Lamprothamnium succinctum in response to hypoosmotic treatment. An increase in the concentration of cytosolic free calcium ion ([Ca2+]c) is prerequisite for the turgor regulation [Okazaki and Tazawa (1990) J. Membr. Biol. 114: 189], We examined whether or not a calcium-dependent protein kinase (CDPK) is involved in the Ca2+-mediated turgor regulation of Lamprothamnium cells. A 53-kDa CDPK which phosphorylated preferentially histone H1 but poorly myelin basic protein or casein, was detected in the cell extract of Lamprothamnium by an in-gel protein kinase assay. This protein kinase was detected by Western blotting and was immunoprecipitated using an anti-Dunaliella tertiolecta CDPK antibody which can neutralize the Dunaliella CDPK activity [Yuasa et al. (1995) Plant Cell Physiol. 36: 699]. The 53-kDa CDPK was partially purified from Lamprothamnium and its activity was shown to be inhibited by the antibody and K-252a, a protein kinase inhibitor. Microinjection of the antibody into the cytosbl of Lamprothamnium cells inhibited the decrease in turgor pressure in response to hypoosmotic treatment. However, a transient increase in [Ca2+]c, which was suggested by a transient reduction of the velocity of cytoplasmic streaming, was induced in antibody-injected cells after hypoosmotic treatment. Turgor regulation upon hypoosmotic treatment was inhibited when the cells were treated with K-252a. These results imply that CDPK of Lamprothamnium functions at a down-stream position of Ca2+-mobilization in processing turgor regulation in response to hypoosmotic treatment.

Keywords: Antibody microinjection; Calcium-dependent protein kinase (CDPK); Lamprothamnium succinctum; Turgor regulation

Journal Article.  0 words. 

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

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