The abundance of alpha-tubulin mRNA increases during ciliary regeneration in Tetrahymena, and this occurs independently of the soluble tubulin content.

Control mechanisms of tubulin synthesis are analyzed during ciliary regeneration of the ciliate Tetrahymena. Titration of the alpha-tubulin mRNA concentrations during the regeneration period reveal that enhancement of tubulin synthesis is preceded and accompanied by increased concentrations of tubulin mRNA molecules. Stimulation of tubulin synthesis is independent of the pool size of soluble tubulin molecules, as suggested by at least two independent lines of evidence: First, like cells of normal phenotype a temperature sensitive size mutant enhances tubulin synthesis as well as tubulin mRNA concentration during ciliary regeneration, although these large mutant cells have a much higher concentration and amount of soluble tubulin molecules in the cytoplasm. Second, slowly regenerating cells of normal phenotype shift-up their concentration of tubulin mRNA molecules already before a time, when ciliary outgrowth might cause a significant depletion of the pool of soluble tubulin molecules. Thus, neither an induction of tubulin synthesis nor an increase in tubulin mRNA molecules is mediated via changes in the pool size of soluble tubulin molecules.