Evidence for the presence ofDNAat basal body sites inTetrahymena pyriformis

The reasons that have led to a search for DNA in the basal body of Tetrahymena pyriformis are twofold: the well-known property of proliferation of this organelle and the possibility that basal body DNA might be involved in its morphogenesis. After a brief review of earlier work the methods employed in this paper are described. To ensure large numbers of cells in a particular state of development organisms were grown in synchronized culture. Animals required for autoradiographic studies were appropriately treated with tritiated thymidine. All investigations were made on the cell cortex or 'ghost' in order to avoid confusion from cell contents. In addition to autoradiography of ghosts, tests were made with acridine orange in the fluorescence microscope. It is concluded from fluorescence tests that basal bodies of T. pyriformis strain S contain DNA. This DNA is not detectable for the first 2 h of the temperature-shock cycle, but is detectable thereafter until cell division. The presence of DNA is confirmed by the autoradiography experiments. The amount of DNA per basal body is estimated very roughly in order of magnitude as 2 $\times $ 10$^{-16}$ g. The origin of basal body DNA is discussed and the possibilities and consequences of the existence of DNA in the homologous centriole are examined in terms of the mitotic cycle, the amoeba-flagellate transformation in Naegleria, and artificial parthenogenesis. The paper concludes with a brief discussion of the genetic implications of basal body DNA.