Figure 8.

The dual-fusion AFB2 biosensor predicts that auxin accumulates in stationary phase cultures. (A) Dose–response curve for auxin at the early stationary phase. Two yeast colonies carrying the AFB2 dual-fusion biosensor respond to exogenous auxin during this phase with an EC₅₀ of 0.003 μM exogenous auxin (SE = 0.00338). (B) Auxin accumulation in the cultures at the late stationary phase (yellow) and a 1 μM auxin spike in the cultures (purple), after 48 h of inoculation, measured by the dual-fusion AFB2 biosensor every 45 min for 6 h. (C) Yeast cultures expressing the AFB2 dual-fusion auxin biosensor were inoculated at varying rates to reach different phases of growth after 16 h of incubation in static fermentative (anaerobic) conditions or shaken (aerobic) conditions. Distributions represent flow cytometric measurements of the ratio of fluorescent intensity areas of AFB2-mScarlet to Venus-Aux/IAA17, which is proportional to the predicted/perceived auxin. Each curve represents the kernel density plot of 10⁴ individual cells. The vertical lines divide the density into quartiles with the middle line representing the median and outer lines representing 25 and 75% of the density.