Dr. Snell proposes to study a newly described secretory event induced during sexual signalling in the biflagellate alga, Chlamydomonas reinhardtii. When mt+ and mt- Chlamydomonas gametes are mixed together, they adhere to each other via adhesion molecules located on their flagellar surfaces. This specific recognition event generates a signal, involving cyclic AMP, leading to activation of actin-filled, acrosome-like mating structures and release of a metalloprotease, lysin. Lysin is responsible for the release and degradation of the cell wall, thus permitting cell fusion and zygote formation. Dr. Snell recently discovered that lysin is stored as an inactive, higher molecular weight, active form by a converting enzyme released during mating. In the studies proposed here he will use standard biochemical methods to isolate and purify the molecule responsible for conversion. The starting material will be the medium collected from mating gametes that had previously been de- walled by the addition of exogenous lysin. Dr. Snell will test the hypothesis that the converting activity is a protease stored in membrane-bounded, intracellular granules. Antibodies will be made against the purified molecule for use in immunolocalization studies at both the light and electron microscopic levels. This work should provide new information about how signal transduction mediated by cell-cell contact brings about a regulated secretory event. %%% The process of fertilization requires that the male and female gamete adhere to each other and subsequently fuse. This requires the limited, localized breakdown of the structures surrounding the cells. Dr. Snell is investigating how the interaction of the gametes triggers the controlled and localized degradation of the constituents surrounding the cells. This will provide detailed molecular information about the requirements for successful fertilization in this model organism.
