Figure 2. AncGR1 and its descendents evolved reduced hormone sensitivity.

Ligand-dependent transcriptional activation of receptors was measured in the presence of increasing concentrations of hormone using a luciferase reporter gene assay. Dose-response curves were calculated for receptor-hormone pairs and plotted as the log effective concentration of hormone for half maximal activation (log EC₅₀) in molar with standard error. Larger values, lower sensitivity; smaller values, higher sensitivity. Hormones are: 11-deoxycorticosterone (DOC), corticosterone (B), 11-dehydrocorticosterone (11-DHC), and 1α-hydroxycorticosterone (1α-B). Cartilaginous fish species are shown in (Figure 1). 11-DHC did not activate cartilaginous fish GRs in our assay (defined as <2-fold activation for EC₅₀>1 µM of hormone) and is not shown for these receptors.