Possible Involvement of Calmodulin and the Cytoskeleton in Electrofusion of Plant Protoplasts

Calmodulin antagonists, trifluoperazine, chlorpromazine, calmidazolium, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), strongly inhibited the electrofusion of barley (Hordeum vulgare L. cv Moor) protoplasts with a marked increase of broken fusion products, after 60 minutes of incubation. W-5, a dechlorinated analog of W-7, was found less effective for the inhibition than W-7. Ethyleneglycol-bis(beta- aminoethylether)-N,N'-tetraacetic acid a Ca(2+) chelator, La(3+), a surface Ca(2+) antagonist, and verapamil, a Ca(2+) channel blocker, also inhibited electrofusion. Dielectrophoresis was inhibited by La(3+). A microtubule inhibitor, vinblastine, inhibited electrofusion strongly while colchicine, slightly. A microfilament inhibitor, cytochalasin B, promoted fused cells to become spherical while phalloidin did not affect electrofusion.