Cytokinin increases intracellular Ca2+ in Funaria: detection with Indo-1.
Changes in intracellular [Ca2+] ([Ca2+]i) after cytokinin-treatment in protonema cells of the moss Funaria hygrometrica have been measured using the pentapotassium salt of Indo-1. The extent of dye loading strongly depended on lowering the pH of the incubation medium to 5.0. Exposing dye-loaded cells briefly with Mn2+ did not quench fluorescence suggesting that the source of fluorescence is from the cytoplasm and not from the cell wall. Indo-1 remains responsive to changes in [Ca2+]i in Funaria cells. The [Ca2+]i in quiescent cells (with and without extracellular Ca2+) is 250 nM, which is within the range of reported [Ca2+]i of other plant cells. Treatment of cells with extracellular cytokinin in 4 mM Ca2+ induced a three-fold increase in [Ca2+]i to 750 nM in target caulonema cells. This increase was not observed in Ca(2+)-free medium. These target cells respond to cytokinin treatment by an asymmetrical division, while non-target chloronema cells do not divide. Cytokinin appears to increase [Ca2+]i by extracellular Ca2+ uptake. However, non-target chloronema cells and tip cells also respond to cytokinin treatment by increasing [Ca2+]i. The differential physiological response of these cell types to hormonal stimulation must lie further down the signal transduction chain.
Hahm
S H
SH
Biology Department, University of South Florida, Tampa.
Saunders
M J
MJ
D002118:Calcium / Q000378:metabolism*; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D003583:Cytokinins / Q000494:pharmacology*; D003593:Cytoplasm / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007211:Indoles / Q000737:chemistry; D008345:Manganese / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D010944:Plants / Q000378:metabolism*; D015398:Signal Transduction; D013194:Staining and Labeling
D003583:Cytokinins; D007211:Indoles; D008345:Manganese; C048960:indo-1; D002118:Calcium