Illustration (IMAGE)
Caption
Asymmetric pheromone signaling in S. cerevisiae and emergence of asymmetric sexual behavior. (A) Alternative routes of how asymmetry in mating behavior may have originated, starting from mating between morphologically identical (isogamous) gametes/ mating types. Commonly, anisogamy with different sizes of gametes is assumed to be a requirement that allowed for emergence of asymmetric sexual behavior by sexual selection. Alternatively, asymmetric mating behavior might have emerged already in isogamous organisms due to molecular asymmetries between gametes. (B) Asymmetric mating determinants of the mating types in Saccharomyces cerevisiae. Molecular components expressed by MATa or MATα cells are shown in red and blue, respectively, and include mating pheromones (a-factor and α-factor), their receptors (Ste2 and Ste3) and a diffusible α-factor protease Bar1 secreted exclusivley by MATa cells. Note that a-factor due to its prenylation (indicated by hydrophobic chain) is considerably more hydrophobic than α-factor.
Credit
Max Planck Institute for Terrestrial Microbiology/Anders
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