Fig. 1. Cdc42 during budding yeast polarization. Budding yeast can polarize in response to two main stimuli: they undergo polarized growth, which leads to budding, and they respond to pheromone gradient during mating by forming a shmoo. These stimuli both lead to Cdc42 recruitment and activation at the site of polarized growth through distinct signalling cascades (pink). Far1p associates with the Cdc42p-GEF Cdc24p and plays a key role in Cdc42p activation. During budding, Far1p degradation allows Cdc24p exit form the nucleus and, during mating, it binds Gß and thereby recruits Cdc24p to the site of polarization. The active, GTP-bound form of Cdc42p (green) regulates multiple direct (solid line) or indirect (dashed line) effectors (blue), which control several cell functions. The co-ordinate polarization of septins, actin and microtubule structures, and of membrane trafficking, allows a polarized growth that leads during budding to the formation of a bud and during mating to the formation of a shmoo.