Genetic control of plasma membrane adhesion and fusion in Chlamydomonas gametes

The final stages of gamete interaction in Chlamydomonas reinhardtii occur between the specialized plasma membrane organelles (mating structures) of opposite mating-type cells. A number of mutants affecting these interactions have been obtained in several laboratories; all have been defined as fusion-defective. This paper demonstrates that there are at least two genetically definable stages of mating-structure interaction: (1) the recognition/adhesion of mating structures, and (2) gamete fusion. The possibility that these two functions, the adhesion and subsequent fusion of mating structures, may be mating-type specific is raised, since of the seven independently isolated mutants analysed, all mutants defective in fusion are of mating-type (-), and only mating type (+) mutants show defects in adhesion.