Genetic analysis of morphogenetic processes in Paramecium: I. A mutation affecting trichocyst formation and nuclear division

Abstract

SUMMARY: Mutation tam38 of Paramecium tetraurelia is a nuclear recessive mutation with a pleiotropic effect on both trichocyst morphogenesis and nuclear processes. The analysis of the defective nuclear processes (micronuclear and macronuclear divisions, nuclear reorganization at autogamy) shows that these defects result from an abnormal localization of the nuclei. Phenocopies of tam38 abnormalities can be obtained by vinblastine treatment of wild-type cells at late stages of division. Taking into account the similarity between tam38 and a series of other mutations which also prevent trichocyst attachment to the cell surface and disturb nuclear divisions, the following interpretation is proposed: the absence of attached trichocyst induces structural changes in the plasma membrane or in the cortical region which disturb the normal cortical control of the localization of nuclei.