| Gametic activation, fusion and their genetic control in Chlamydomonas monoica were analyzed. Cell wall lysis, as a necessary prelude for cell fusion, is shown to require flagellar agglutination between competent gametes. The lysis of the gamete wall is specifically restricted to the region surrounding the growing mating structure. The initial breaking point of the cell wall is always associated with the mating structure tip immediately underneath. The hole on the cell wall is enlarged as the mating structure passes through. The cell fusion process is mediated by this cellular extrusion--mating structure activation in response to flagellar agglutination. The mating structure is the extension of the preexistin plasma papilla. In each mating pair, one cell always has a longer mating structure extending out of the wall, while the other cell always has a shorter mating structure that emerges only slightly from the broken wall. The longer mating structure has a large vesicle at the tip which is the most important character distinguishing the two types of mating structures. The cytoplasmic bridge forms as the mating structures of opposite mating type gametes fuse together.;The gene locus mtl-7 which controls gamete cell fusion was identified. This mt... |
