Calcium channel blocker and calmodulin antagonists affect the gradient of free calcium ions in lily pollen tubes.
The distribution of intracellular free calcium ions ([Ca2+]i) was measured in pollen tubes of Lilium longiflorum using video imaging microscopy and the calcium sensitive indicators fura-2 and quin-2. The mean [Ca2+]i in growing pollen tubes measured with fura-2 shows a maximum of 1.7 to 2.6 microM in the tube tip and decreases almost exponentially to 60 to 100 nM at 100 microns behind the tip. Using quin-2, the maximum [Ca2+]i was also found in the tube tip but with a lower Ca2+ concentration, namely 1 microM. Addition of the calcium channel blocker La3+ caused a decrease of the [Ca2+]i maximum in the tube tip, indicating a heterogeneous distribution of Ca2+ channels along the plasma membrane of pollen tubes. The [Ca2+]i increased after addition of vanadate or compound 48/80. This suggests an involvement of a calmodulin-dependent Ca2+ pump in generation of the Ca2+ gradient in lily pollen tubes. The high [Ca2+]i found in the tube tip with fura-2 seems to indicate the real Ca2+ concentration and is probably responsible for vesicle fusion, fragmentation of actin filaments, and inhibition of cytoplasmic streaming.
Obermeyer
G
G
Botanisches Institut I, Universität Karlsruhe (TH), Bundesrepublik Deutschland.
Weisenseel
M H
MH
D000634:Aminoquinolines / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002147:Calmodulin / Q000037:antagonists & inhibitors*; D016764:Cell Polarity / Q000187:drug effects / Q000502:physiology*; D005456:Fluorescent Dyes / Q000378:metabolism; D016257:Fura-2 / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D007811:Lanthanum / Q000494:pharmacology; D011058:Pollen / Q000187:drug effects / Q000378:metabolism*; D014638:Vanadates / Q000494:pharmacology; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
D000634:Aminoquinolines; D002121:Calcium Channel Blockers; D002147:Calmodulin; D005456:Fluorescent Dyes; D014638:Vanadates; D003189:p-Methoxy-N-methylphenethylamine; D007811:Lanthanum; C035739:Quin2; D002118:Calcium; D016257:Fura-2