ON SEXUAL AGGLUTINATION AND MATING-TYPE SUBSTANCES (GAMONES) IN ISOGAMOUS HETEROTHALLIC CHLAMYDOMONADS. II. THE EFFECT OF CONCANAVALIN A UPON THE MATING-TYPE REACTION

¹ Department of Biological Science, Florida State University, Tallahassee, Florida 32306

Concanavalin A (CONA) isoagglutinates the gametes within each sex of Chlamydomonas eugametos. C. moewusii syngen I, and C. moewusii syngen II by a typical agglutinative adhesion of the flagella tips. Incubation of gametes with lower CONA-concentrations which do no longer cause isoagglutination, effects blockage of the mating-type activity in only one of the two sexes, the other one being unaffected. In the three taxons investigated, it is always the androgametes which are sensitive to CONA. In addition, CONA immobilizes the cells after a short period of time. The CONA-induced isoagglutinations of both gamete types, the immobilization, and the unilateral blocking of one mating-type activity can be reversed entirely by mannose. In the three taxons, the unilateral sensitivity of the mating-type reaction to CONA is reciprocal to a unilateral sensitivity to 0.1% trypsin. Gynogametes, sexually inactivated by trypsin, still interact with CONA. In each of the three taxons, CONA precipitates both sexual isoagglutinins but only one of them, that of the CONA-insensitive sex, in active form. The data are discussed as to their bearing on the nature of the initial contact mechanism between sex cells.

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