Involvement of Tetrahymena intermediate filament protein, a 49K protein, in the oral morphogenesis

To study the biological function of Tetrahymena intermediate-type filament protein (a 49K protein), we examined the immunofluorescence localization of 49K protein within Tetrahymena cells. The results showed that the immunofluorescence was localized in the oral apparatus, mitochondria and mucocysts. Among them, the fluorescence in the oral apparatus was of high interest in its unique region and vicissitude in the cell cycle: a tau-shaped region of the oral apparatus intensely fluoresced during interphase, but the fluorescence completely disappeared during dividing phase. The tau-shaped region corresponded to 'posterior connectives' and the root part of 'deep fiber', to the conjunction parts of microtubule bundles. In the those parts, there was electron-dense material in the microtubule bundles. Hence, it is conceivable that 49K protein corresponds to the dense material and has a function of microtubule bundle conjunction. On the other hand, disappearance of immunofluorescence from the old oral apparatus of most dividing cells reflected the oral apparatus regression and remodelling which have been known as necessary sequential events in the cell cycle. We observed that oral fluorescence disappeared concurrently with the onset of oral regression and of constriction of division furrow, whereas at a late dividing stage immunofluorescence began to appear simultaneously in both new and old oral apparatus. Thus, the 49K protein may play a crucial role(s) not only in the morphogenesis of oral primordia but also in the transient morphogenesis in the old oral system.