Trifluoperazine and W-7 inhibit mating in Chlamydomonas at an early stage of gametic interaction

Gametic mating by Chlamydomonas reinhardi is inhibited in a dose-dependent and reversible manner by the calmodulin antagonists trifluoperazine (TFP) and W-7, but not by W-5, an analog of W-7 having lower affinity for calmodulin. Quantitation of the sequential steps of mating showed that TFP and W-7 both allow normal levels of flagellar agglutination but prevent all subsequent steps. Gametes agglutinate aberrantly and do not form mating pairs. Further, both of these drugs prevent the translocation of latex beads along the flagellar surface. Our observations suggest that calmodulin may play an integral role in the translocation of flagellar adhesion sites during the tip-locking stage of the Chlamydomonas mating reaction. Flagellar surface motility may be crucial to the transduction of signals during mating and may share regulatory mechanisms with other forms of surface motility.