Theoretical modeling of the Aux/IAA negative feedback circuit in plants

• The plant growth regulator auxin has been shown to be involved in regulating a diverse range of developmental processes in plants.
• Auxin can induce the Aux/IAA genes and its related signal network contains several negative feedback loops, whereby Aux/IAA proteins auto-repress its own genes with the help of auxin response factor (ARF).
• Here, we present a system-theoretic approach to quantitatively model a single Aux/IAA negative feedback loop, which can be implemented deterministically and stochastically.
• The results show that the model has a single steady-state in deterministic simulation but oscillates in stochastic simulation.
• By sensitivity analysis, we identify the ARF turnover and formation as key parameters in the model.
• These observations may shed light on recent experimental results.

The plant growth regulator auxin has been shown to be involved in regulating a diverse range of developmental processes in plants. Auxin can induce the Aux/IAA genes and its related signal network contains several negative feedback loops, whereby Aux/IAA proteins auto-repress its own genes with the help of auxin response factor (ARF). Here, we present deterministic and stochastic numerical simulations to model a single Aux/IAA negative feedback loop, which can be implemented deterministically and stochastically. The results show that the model has a single steady-state in deterministic simulation but oscillates in stochastic simulation. The inferred dynamic properties of the Aux/IAA negative feedback circuit are well consistent with previous experimental observations. By sensitivity analysis, we identify the ARF turnover and production as key parameters in the model. Besides, the quantified noise strength along the loop demonstrates that the ARF can increase the noise of Aux/IAA protein and mRNA. These observations may shed light on recent experimental results.