Figure 4.

Characteristics of the SI-stimulated Ca²⁺-permeable conductance. SI was induced by the addition of PrsS₃ + PrsS₈ to pollen protoplasts (haplotype S₃ or S₈), bathed in Ca²⁺-containing saline. Currents were elicited using the voltage ramp protocol. A, Mean SI-induced current (n = 4) measured in saline containing 10 mm CaCl₂ (black squares), then in saline where CaCl₂ was replaced with calcium gluconate (white squares). B, A representative set of raw traces for whole cell current recorded from the same protoplast at different Ca²⁺ concentrations. C, Mean data for the effect of different Ca²⁺ concentrations on SI-induced currents (n = 3). D, The mean SI-induced current at −100 mV in Ca²⁺-containing medium (Ca²⁺) and in medium where CaCl₂ was replaced by BaCl₂ (Ba²⁺; n = 7). E, The mean SI-induced current (n = 12) at −100 mV in Ca²⁺-containing medium (Ca²⁺) and in medium where CaCl₂ was replaced by MgCl₂ (Mg²⁺). F, SI-induced currents recorded at −100 mV, in standard Ca²⁺-containing medium (untreated control; black squares), after addition of incompatible PrsS (white squares) and after subsequent addition of 500 μm La³⁺ (white triangles). The current induced by incompatible PrsS was completely abolished (n = 3). G, SI-stimulated currents recorded at −100 mV were tested for sensitivity to verapamil. The I-V curves (n = 3) are shown after addition of incompatible PrsS, first in standard Ca²⁺-containing medium (black squares) and then after addition of 50 μm verapamil (white squares). All data are means ± se.