CHEMOATTRACTION OF MALE GAMETES BY A PHEROMONE PRODUCED BY FEMALE GAMETES OF CHLAMYDOMONAS

In isogamous species of Chlamydomonas, such as Chlamydomonas reinhardt ii and Chlamydomonas eugametos, the sexual process involves the use of flagella agglutinins by which the gametes of compatible strains adher e through chance encounter and ultimately pair and fuse to form zygote s. In a newly described heterogamous species, Chlamydomonas allenswort hii, the sexual process is initiated by the chemoattraction of small s perm to a sexually competent female gamete, which continues to secrete the pheromone until it has fused with one of the sperm so attracted. From bacteria-free female strains of C. allensworthii, the chemoattrac tant has been isolated and identified as a pentosylated hydroquinone ( M(r) = 532) whose spectral, chemical, and physical properties are in a ccord with the structure of a xymethyl)-1,4-benzohydroquinone-1-(beta- xyloside). A rapid bioassay of the pheromone uses DEAE-Toyopearl 650M beads to which the pheromone adsorbs, When such activated beads are pl aced in a suspension of sperm, they act as surrogate females and attra ct the small motile sperm, The purified pheromone shows activity at a concentration as low as 1 pM.