Wall appositions induced by ionophore A 23187, CaCl2, LaCl3, and nifedipine in characean cells |
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Authors: | Ilse Foissner |
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Institution: | (1) Institut für Pflanzenphysiologie, Universität Salzburg, Salzburg |
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Abstract: | Summary The formation of wall appositions (plugs) by ionophore A 23187, CaCl2, LaCl3, and nifedipine was studied in mature internodal cells of characeaen algae. CaCl2 at concentrations above 10–2M induces thick fibrillar plugs without callose inNitella flexilis. InChara corallina andNitella flexilis ionophore A 23187 (1.25×10–5 to 5×10–5M) and LaCl3 (7.5×10–5 to 2.5×10–4M) cause flat appositions which contain callose and have a more granular structure. Plug formation by ionophore A 23187, CaCl2, and LaCl3 is pH-dependent and occurs beneath the alkaline regions of the cell. Nifedipine (10–4 to 10–5M) induces plugs inNitella flexilis after previous injury. These callose-containing wall appositions consist of a heterogeneous granular core which is covered by a fibrillar layer. The results of this work are compared with previous studies on wound wall formation and chlortetracycline (CTC)-induced plug formation which reveal that abundant coated vesicles occur only when a thick fibrillar wall layer is formed. Neither LaCl3 nor nifedipine inhibit the formation of CaCl2- or CTC-plugs. The unusual effects of these substances, which normally act as Ca2+ antagonists and therefore should prevent and not induce plug formation, are discussed. It is suggested that La3+ mimicks the effects of calcium and that nifedipine binding to the Ca2+ channels is altered in the alkaline regions of characean internodes and allows an influx of Ca2+.Abbreviations AFW
artificial fresh water
- CTC
chlortetracycline
- DCMU
dichlorphenyldimethylurea
- DMSO
dimethylsulfoxide
- EGTA
ethyleneglycoltetraacetic acid
- MES
2-(N-morpholino) ethanesulfonic acid
- HEPES
N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid
- TAPS
N-trishydroxymethyl]methyl-3-aminopropanesulfonic acid |
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Keywords: | Wall appositions Ca2+ lonophore A 23187 La3+ Nifedipine Vesicle Coated Nitella Chara |
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