Fig 8. The trade-off between robustness and efficiency.
(A) Efficiency is defined as the total nutrient uptake of a single transporter over its average lifetime. As activity-dependent downregulation increases (orange, blue and purple lines with direction of increase denoted by blue arrows), robustness increases and efficiency decreases. The minimal value of robustness depends on the Sext (black line). Therefore, as Sext increases (black arrow), the slope of the efficiency-robustness trade-off increases (orange versus blue versus purple lines). (B) Robustness-efficiency trade-off in a system with only activity-dependent downregulation (solid lines) or with activity-dependent downregulation and internal nutrient regulation of transporter synthesis (dashed lines). Adding internal nutrient dependent transporter regulation results in improving the minimal robustness limit and the robustness-efficiency trade-off. As n increases so does the improvement in the trade-off (S1 Appendix, section VIII, S2 Fig, Fig 7).