Figure 4.

(a) Top: In the presence of auxin, AFB degrades the fusion protein EYFP-AUX/IAA. Bottom: A model from previous work⁶ of the network shown. State x represents auxin bound to AFB with input u being the auxin concentration, parameter k₁ the association rate of auxin and AFB, and k₂ the natural degradation rate of AFB. State y represents the concentration of EYFP-AUX/IAA where k₃ is the production rate, k₄ is the natural degradation rate, and k₅ is the degradation rate in the presence of auxin bound to AFB. (b) YKL73 characterized in a turbidostat at four different ODs. At t = 1.25 h auxin was added to the culture chamber and media source to reach a concentration of 10 μM, and the response was measured by sampling effluent and reading mean fluorescence in a flow cytometer at a period of roughly 6 min. The cytometery data was gated to only include singlet (nonbudding) yeast in a healthy size range. An untreated time course is available as Supporting Information Figure S9 and shows no singnifigant change in fluorescence. (c) Model parameter k₅ was fit to the data collected in part b (See Havens et al.⁶ Supplemental Data for detailed methods) and compared to previous work (gray).⁶