A suppressor gene involved in chemical induction of conjugation in Paramecium aurelia.

A dominant gene Su(kau-2) partially suppresses the effect of an apparently unlinked recessive kau-2. Gene kau-2 blocks chemical induction of conjugation in Paramecium aurelia syngen 8 when solutions of acriflavine + either KCl or MgCl-2 are used. Wild-type cells are induced to conjugate in either solution. When cells homozygous for kau-2 also have gene Su(kau-2), they are still uninducible in the solution containing KCl, but become inducible in the MgCl-2 solution. Analysis of the concentrations of solutions which are effective in induction of conjugation of various genotypes shows that the action of Su(kau-2) is not a simple restoration of wild-type phenotype since certain novel features of the suppressor can be seen. Analysis of the duration of ciliary reversal of various genotypes suggests that one necessary step in chemical induction of conjugation is a certain magnitude of depolarization of the surface membrane of the cell.