Ca2+-sensitive and Ca2+-insensitive exocytosis in maize coleoptile protoplasts.
Ca2+ and osmotic driven extension of the surface area of maize coleoptile protoplasts was investigated using capacitance measurements and photolysis of the caged compound DM-nitrophen. Protoplasts responded to an elevation of cytoplasmic Ca2+ (Ca(i)) with a rapid burst in capacitance reaching a maximal increase of 1.3+/-1.1% over the resting cell capacitance. Subsequent lowering of the osmotic potential in the external medium by 210 mosmol caused a further increase in Cm by 26+/-6%. These data indicate two independent pathways for insertion of membrane into the plasma membrane. One is driven by Ca(i) and recruits membrane from a small pool. The osmotic evoked rise in surface area draws membrane from a much larger reservoir and may be driven by membrane tension.
Thiel
G
G
A.v.H. Inst. Plant Sciences, Göttingen.
Sutter
J U
JU
Homann
U
U
D000085:Acetates / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002614:Chelating Agents / Q000494:pharmacology; D003470:Culture Media; D004553:Electric Conductivity; D005029:Ethylenediamines / Q000494:pharmacology; D005089:Exocytosis / Q000502:physiology*; D009995:Osmosis; D010782:Photolysis; D011523:Protoplasts / Q000378:metabolism* / Q000502:physiology; D003313:Zea mays / Q000166:cytology / Q000378:metabolism* / Q000502:physiology
D000085:Acetates; D002614:Chelating Agents; D003470:Culture Media; D005029:Ethylenediamines; C057014:DM-nitrophen; D002118:Calcium