Involvement of Ca2+ in Vacuole Degradation Caused by a Rapid Temperature Decrease in Saintpaulia Palisade Cells: A Case of Gene Expression Analysis in a Specialized Small Tissue.
Saintpaulia (African violet) leaves are known to be damaged by a rapid temperature decrease when cold water is applied to the leaf surface; the injury is ascribed to the chloroplast damage caused by the cytosolic pH decrease following the degradation of the vacuolar membrane in the palisade cells. In this report, we present evidence for the involvement of Ca(2+) in facilitating the collapse of the vacuolar membrane and in turn in the temperature sensitivity of Saintpaulia leaves. In the presence of a Ca(2+) chelator (EGTA) or certain Ca(2+) channel inhibitors (Gd(3+) or La(3+)) but not others (verapamil or nifedipine), the pH of the vacuole, monitored through BCECF (2',7'-bis(carboxyethyl)-4 or 5-carboxyfluorescein) fluorescence, did not increase in response to a rapid temperature drop. These pharmacological observations are consistent with the involvement of mechanosensitive Ca(2+) channels in the collapse of the vacuolar membrane. The high level of expression of an MCA- (Arabidopsis mechanosensitive Ca(2+) channel) like gene, a likely candidate for a mechanosensitive Ca(2+) channel(s) in plant cells, was confirmed in the palisade tissue in Saintpaulia leaves by using a newly developed method of gene expression analysis for the specialized small tissues.
Department of Biology, Graduate School of Science, Kobe University, Rokkodai-cho 1-1, Nada-ku, Kobe, 657-8501 Japan.
Miwa
M
Ohnishi
Department of Biology, Graduate School of Science, Kobe University, Rokkodai-cho 1-1, Nada-ku, Kobe, 657-8501 Japan.
Noriaki
N
Kadohama
Department of Biological Science, Graduate School of Science, Kanagawa University, Tsuchiya 2946, Hiratsuka, Kanagawa, 259-1293 Japan.
Yoshihiro
Y
Suzuki
Central Research Laboratory, Hitachi, Ltd., 1-280 Higashi-Koigakubo, Kokubunji-shi, Tokyo, 185-8601, Japan.
Tomoharu
T
Kajiyama
Department of Biology, Graduate School of Science, Kobe University, Rokkodai-cho 1-1, Nada-ku, Kobe, 657-8501 Japan.
Chizuko
C
Shichijo
Department of Biology, Graduate School of Science, Kobe University, Rokkodai-cho 1-1, Nada-ku, Kobe, 657-8501 Japan.
Kimitsune
K
Ishizaki
Department of Biology, Graduate School of Science, Kobe University, Rokkodai-cho 1-1, Nada-ku, Kobe, 657-8501 Japan.
Hidehiro
H
Fukaki
Department of Biology, Tokyo Gakugei University, Koganei-shi, Tokyo, 184-8501 Japan.
Hidetoshi
H
Iida
Central Research Laboratory, Hitachi, Ltd., 1-280 Higashi-Koigakubo, Kokubunji-shi, Tokyo, 185-8601, Japan.
Hideki
H
Kambara
Department of Biology, Graduate School of Science, Kobe University, Rokkodai-cho 1-1, Nada-ku, Kobe, 657-8501 Japan mimura@kobe-u.ac.jp.
Tetsuro
T
Mimura
D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D065096:Calcium Chelating Agents / Q000494:pharmacology; D003080:Cold Temperature; D004533:Egtazic Acid / Q000494:pharmacology; D005452:Fluoresceins / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007425:Intracellular Membranes / Q000378:metabolism; D007473:Ion Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D019684:Magnoliopsida / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D009543:Nifedipine / Q000494:pharmacology; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014617:Vacuoles / Q000378:metabolism*; D014700:Verapamil / Q000494:pharmacology
D002121:Calcium Channel Blockers; D065096:Calcium Chelating Agents; D005452:Fluoresceins; D007473:Ion Channels; C057433:2',7'-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester; D004533:Egtazic Acid; D014700:Verapamil; D009543:Nifedipine; D002118:Calcium
Ca2+; MCA; Mechanosensitive channel; Saintpaulia; Temperature stress; Vacuole degradation