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"Budding yeast haploid cells exist as two sexual types, called MATa and MATalpha. They can attract each other to mate by producing specific pheromone. This production of pheromone can be detected by cells which then form a mating projection, called a shmoo, in the direction of their mating partner. When two shmoos reach one another, the two cells fuse and produce a diploid cell. Here a MATa cell was exposed to a spatial gradient of alpha factor (imaged in red), the pheromone normally emitted by the MATalpha cells. This artificial gradient was produced using synthesized alpha factor flown in a ""two phases laminar flow chamber"", the MATa cells being attached on a coverslip closing the chamber. In green is shown the localization of the MAP kinase Fus3, specific for the pheromone response pathway, coupled to a yellow fluorescent protein, YFP. This MAP kinase is usually concentrated only in the nucleus and relocates at the tip of the mating projection when cells polarize and grow in the direction of a pheromone gradient." |
