Level of active Slt2p/Mpk1p, Fus3p and Kss1p detected with phospho-p42p44 antibody. (A) Active Slt2p/Mpk1p in S288c, W303, ∑1278b backgrounds. (B) Active Slt2p/Mpk1p, Kss1p and Fus3p in S288c BY4741 and ste4 Δ, ste5 Δ, ste11 Δ, ste50 Δ, fus3 Δ, kss1 Δ null derivatives. Cells were exponentially grown in YEPD in A. and in SC selective medium with 2% dextrose in B. The data in Figure 1A are from a reprobing of a published immunoblot of active Kss1p and Fus3 (Supplemental Figure Two of Andersson et al., 2004 ).