Autoradiographic evidence for self-fertilization in Tetrahymena thermophila

Conjugation in Tetrahymena thermophila consists of a sequence of nuclear events, including meiosis and reciprocal cross-fertilization, which result in biparental genetic endowment of the sexual progeny. Genetic evidence was recently provided that the normal exchange of gametic nuclei between conjugating cells can be efficiently blocked by hyperosmotic shock. In this paper we confirm this finding autoradiographically. We also report that the inhibitor of microtubule assembly, vinblastine, also blocks this step, as well as the subsequent fusion of gametic nuclei. The ability of conjugating cells to survive and continue more or less normally after blocks of self-fertilization and pro-nuclear fusion demonstrates a surprisingly high degree of developmental regulation during conjugation. Self-fertilization has proven useful for the isolation of recessive mutants in T. thermophila.