Illustration of the mating steps regulated by the distal and proximal actions of M-factor mating pheromone in liquid culture.

<p>When haploid cells of the opposite mating types are mixed in nitrogen-free liquid medium, cell agglutination occurs after arrest of cell division. Mating type-dependent cell-to-cell adhesion is induced in cell aggregates. From the contact site, polarized tip growth occurs leading to cell fusion. Pheromone is required for steps of cell agglutination (distal action), polarized growth and cell fusion (proximal action).