Reciprocal induction of cell division by cells of complementary mating types in Tetrahymena

Abstract

Tetrahymena cells of complementary mating types begin their pairing reaction 3 h after they are transferred to starvation buffer and mixed together. At the same time a division wave involving most but not all cells of both mating types is seen. If cells of each mating type are starved separately, no division wave occurs, thus indicating that cells of complementary mating types are capable of an interaction that leads to a reciprocal induction of a synchronous cell division. The basis for the interaction appears not to be mediated by a released factor but instead requires the physical presence of the differing cell types. Cells are sensitized to the interaction by a 2-h starvation period, at which time a surface transformation may occur, making possible a contact-induced stimulation. At 2 h after starvation all cells are either in G1 (arrested) or in G2, indicating that it is G2 cells that respond to the interaction. Nonetheless, G1 cells are capable of inducing the division on the complementary mating type.