Mating type specific induction of cell wall lytic factor by agglutination of gametes in Chlamydomonas reinhardtii

When mt+ and mt− gametes of Chlamydomonas reinhardtii were mixed, shedding of cell walls took place in both mating types during massive agglutination and/or pairing. This was caused by a cell wall lytic factor that had been induced by flagellar agglutination and excreted into the medium by cells concurrently with their cell wall release. When glutaraldehyde-fixed gametes and isolated flagella of one mating type caused isoagglutination of live gametes of the other mating type, the live mt+ gametes induced the lytic factor and shed their walls, whereas none of the live mt− did this. The cell walls of mt− gametes were lost only when the lytic factor, which had been excreted by mt+ gametes into the medium, acted from the outside. These data imply that mt+ gametes are responsible for the induction of the lytic factor by agglutination, which acts on cell walls of both mating types either endogenously or exogenously.