title: Nucleogenesis and stomatogenesis in sexual reproduction of Paramecium tetraurelia may be controlled by chromosomal factors of the germ nucleus (micronucleus).
abstract: The nature of control of development of the nucleus and the oral apparatus by the germ nucleus (micronucleus) during sexual reproduction in Paramecium tetraurelia was analyzed by studying nine euploid (mostly haploid) clones. These clones were generated by conjugation between cells lacking micronuclei (amicronucleates) and micronucleates with diploid micronuclei. All except two of the euploid clones were normal in stomatogenesis in asexual reproduction. In contrast, during subsequent sexual reproduction (autogamy), eight of the euploid clones showed correlative abnormalities in nucleogenesis and stomatogenesis. The former involves the generation of gametic nuclei and the postzygotic development of micronuclei and macronuclear anlagen. The latter involves the crucial stomatogenic step of initiation of oral membraneile assembly, as well as the specification of the normal pattern of the oral apparatus. Since during autogamy haploid nuclei underwent meiosis giving rise to aneuploid nuclei and thus genomic imbalance, the present findings support the notion that micronuclear chromosomal factors contribute to both nucleogenesis and stomatogenesis in the sexual cycle.
authors.affiliation: Zoology Department, University of Hong Kong, Hong Kong.
authors.forename: M F
authors.initials: MF
authors.lastname: Chau
authors.forename: S
authors.initials: S
authors.lastname: F Ng