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Journal of Cell Science, Vol 95, 293-301, Copyright © 1990 by Company of Biologists

Submitted on August 29, 1989
Accepted on November 14, 1989

Contact activation in Chlamydomonas gametes by increased binding capacity of sexual agglutinins

A. M. TOMSON 1, R. DEMETS 1, A. MUSGRAVE 1, R. KOOIJMAN 1, D. STEGWEE 1, and H. VAN DEN ENDE 1

1 Plantenfysiologisch Laboratorium, Vakgroep Moleculaire Celbiologie, Universiteit van Amsterdam, Kmislaan 318, NL-1098 SM Amsterdam, The Netherlands

When the flagella of compatible gametes of Chlamydomonas eugametos contact one another, the capacity for sexual adhesion is rapidly increased. It is shown that during this so-called contact activation the amount of adhesion molecules, or agglutinins, on the flagellar surface remains relatively constant, indicating that the increase in sexual adhesiveness is mainly the result of an enhancement in binding capacity of the agglutinins. Contact activation coincides with an apparent aggregation of agglutinins in association with a weakening of the agglutinin binding to the membrane. Artificial clustering of the agglutinins, using the lectin wheat germ agglutinin, also leads to an increase in sexual adhesiveness. In the presence of anti-tubulin drugs compatible gametes make contact with one another but fail to increase their adhesiveness. It is proposed that micro-aggregation of agglutinin molecules, mediated by tubulin, underlies the enhancement of sexual binding capacity.

Key words: Chlamydomonas, gametes, adhesion, sexual agglutinins, contact activation

Submitted on August 29, 1989
Accepted on November 14, 1989






© The Company of Biologists Ltd 1990