Hereditary blocks in postconjugational oral morphogenesis in Tetrahymena thermophila

During conjugation in Tetrahymena thermophila, oral structures undergo partial regression and remain “frozen” at this stage until cell separation. Then the exconjugant cells resume in situ oral reorganization, which is the prerequisite for their feeding and survival. First, the old oral membranelles are completely resorbed and new ciliary basal bodies proliferate into an “anarchic field”. Then they are assembled into new oral membranelles. Two hereditary blocks in T. thermophila postconjugational oral morphogenesis leading to cell death were observed: i) In one genetic variant, the cells which were arrested (or at least strongly delayed) in cell separation were also arrested in resorption of old macronuclei and failed to resume oral morphogenesis; they remained “frozen” at the stage of partially regressed oral structures i.e. they did not resorb old oral membranelles and failed to proliferate new basal bodies. ii) In another genetic variant, the nuclear events, cell separation and proliferation of new basal bodies into the “anarchic field” took place at the same time as in control conjugation, but then the exconjugants were arrested in assembly of new oral membranelles, ultimately becoming astomatous. This arrest of stomatogenesis was not observed during somatic oral replacement.