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

元データ 日本植物生理学会


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 ([Ca^<2+>]_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 Ca^<2+>-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 cytosol of Lamprothamnium cells inhibited the decrease in turgor pressure in response to hypoosmotic treatment. However, a transient increase in [Ca^<2+>]_c, which was suggested by a transient reduction of the velocity of cytoplasmic streaming, was induced in anti-body-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 Ca^<2+>-mobilization in processing turgor regulation in response to hypoosmotic treatment.


Iwasaki Naohiko Dept. Biol. Osaka Med. College
Iwasaki Naohiko Department Of Biology Osaka Medical College
Iwasaki Naohiko Osaka Medical College Department Of Biology
Iwasaki Naohiko Dept. Biol. Osaka Med. Coll.
MUTO Shoshi Nagoya University Bioscience Center, Nagoya University
Muto S Nagoya University Bioscience Center Nagoya University:graduate School Of Agricultural Sciences Nagoy
Yuasa T Nagoya University Bioscience Center Nagoya University
Yuasa Takashi Nagoya University Bioscience Center
Okazaki Yoshiji Department of Biology, Faculty of Science, University of Tokyo
Okazaki Yoshiji Department Of Biology Faculty Of Science University Of Tokyo
Muto Shoshi Nagoya University Bioscience Center
Yuasa Takashi Graduate School Of Bioagricultural Sciences Nagoya University
Muto Shoshi Nagoya Univ. Bioscience Center And Graduate School Of Bioagricultural Sciences
Okazaki Yoshiji Dept. Biol., Osaka Med. College