Fig. 4.

Selection on the ERG pathway. (A) Final steps of the ergosterol biosynthesis pathway. Targets of reinforcing cis/trans pairs are shown in red. Note Erg25 and Erg26 actually catalyze a series of four reactions, shown here collapsed into one arrow, and Erg28 is not an enzyme but an important regulator of the reaction shown. (B) Results of θ distribution test, similar to Fig. 3C except using only the six ERG genes highlighted in A for the targets of reinforcing eQTL. (C) Phylogenetic tree of yeast strains, with the most parsimonious location of the HAP1 Ty1 insertion (blue) and possible times of ERG gene selective sweeps on down-regulating cis-regulatory variants (red). Note that other ERG gene sweeps may also have occurred more recently than shown; polymorphism data from additional laboratory strains will be needed to test this.