J. Messiaen et al., CALLOSE SYNTHESIS IN SPIROSTANOL TREATED CARROT CELLS IS NOT TRIGGERED BY CYTOSOLIC CALCIUM, CYTOSOLIC PH OR MEMBRANE-POTENTIAL CHANGES, Plant and Cell Physiology, 36(7), 1995, pp. 1213-1220
Carrot (Daucus carota L.) cell suspensions were treated with a spirost
anol saponin from Yucca. This saponin is an elicitor of callose synthe
sis. Irrespectively of the mode of action of spirostanol on the callos
e synthase activity itself, the spirostanol-induced callose synthesis
in carrot is not preceded by changes in membrane potential, cytosolic
free calcium or cytosolic pH. The inability of modulators of cytosolic
free calcium content (verapamil, nifedipine and Br-A23187), EGTA and
a proton pump inhibitor (vanadate) to inhibit or induce callose format
ion is consistent with a calcium- and pH-independent mechanism for cal
lose deposition.