Regeneration of Cilia in Starved Tetrahymena Thermophila Involves Induced Synthesis of Ciliary Proteins but Not Synthesis of Membrane Lipids

The synthesis of ciliary-membrane phospholipids and ciliary proteins was studied after deciliation in starving Tetrahymena thermophila cells. Deciliated cells regenerated the new ciliary membrane without any induced phospholipid synthesis. The constant cell volume found during the regrowth of the cilia suggests that renewal of ciliary membranes takes place by insertion of intracellular membrane material into the cell surface. In contrast with the absence of induced phospholipid synthesis during ciliary regeneration, the synthesis of ciliary proteins was found to be induced. This enhanced synthetic activity was made possible by an increased rate of intracellular protein degradation in regenerating cells. It was found that the extent of the induced synthesis strongly depends upon the growth conditions of the cells before starvation. Furthermore, it was shown that the degree of induced protein synthesis is greater for higher-molecular-weight ciliary proteins than for lower-molecular-weight species.