Fig. 3.

Model for the role of Bar1 protease in white and opaque MTL a cells of C. albicans. Opaque cells exposed to pheromone highly upregulate the expression of the BAR1 gene. This upregulation results in sufficient secretion of Bar1 protease to prevent auto-activation of the mating program. However, it is predicted that in certain niches Bar1 activity is sequestered/degraded allowing for opaque cells to initiate autocrine pheromone signaling and undergo efficient same-sex mating. In contrast, when white cells are exposed to pheromone, they do not respond by upregulating expression of BAR1. It is therefore possible that the level of secreted Bar1 is insufficient to degrade exogenous α-pheromone, making these cells highly sensitive to the effects of pheromone and allowing for pheromone-enhanced biofilm formation to occur