Journal of Cell Science, Vol 95, 287-291, Copyright © 1990 by Company of Biologists

Submitted on September 11, 1989
Accepted on October 24, 1989

Monoclonal antibody against a conjugation-specific nuclear antigen in Paramecium caudatum

¹ Biological Institute, Tohoku University, Sendai 980, Japan

To understand molecular mechanisms controlling the sexual reproduction process (conjugation) in Paramecium caudatum, we have tried to detect conjugation-specific antigens with monoclonal antibodies. We obtained a monoclonal antibody (CSN-1) against an antigen that appears in the nuclei only during conjugation. This nuclear antigen began to appear both in micro- and macronuclei at micronuclear stage II or III early in the conjugation process (4 h after the mating reaction at 25°C). In the macronucleus, the nuclear antigen persisted until the stage of macronuclear fragmentation (about 35 h) and then disappeared before degeneration of the macronuclear fragments. In the micronucleus, the antigen existed until the crescent stage (stage V) of the first meiotic division (8h). The antigen in the micronucleus disappeared after the crescent stage but reappeared again in the eight nuclei produced by the third postzygotic division (25 h). Then it persisted only in the four macronuclear anlagen differentiated from the eight nuclei (about 30 h). When exconjugant cells had undergone two successive postconjugational cell divisions and thus possessed only one new macronucleus as in the vegetative cells, the antigen disappeared completely from the new macronucleus in most cells. These cells without the antigen began to appear about 50 h after the mating reaction. As the antigen is specific to conjugation and localized in nuclei, it may play some important role(s) in the conjugation process.

Key words: conjugation, conjugation-specific antigen, meiosis, monoclonal antibody, nucleus, nuclear antigen, Paramecium caudatum

Submitted on September 11, 1989
Accepted on October 24, 1989