Ca-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+(Cai) 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 Cmby 26±6 %. These data indicate two independent pathways for insertion of membrane into the plasma membrane. One is driven by Caiand 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.
Gerhard Thiel A.v.H. Inst. Plant Sciences, Untere Karspüle2 D-37073,Göttingen., , , ,.
Gerhard
G
Thiel
Gerhard Thiel A.v.H. Inst. Plant Sciences, Untere Karspüle2 D-37073,Göttingen., , , ,.
Jens-Uwe
JU
Sutter
Gerhard Thiel A.v.H. Inst. Plant Sciences, Untere Karspüle2 D-37073,Göttingen., , , ,.
Ulrike
U
Homann
Key words Ca2+-dependent/ Ca2+-independent exocytosis; Zea mays coleoptile cells; capacitance; cell elongation.; membrane tension