A Model of the Ethylene Signaling Pathway and its Gene Response in Arabidopsis thaliana: Noise-Filtering Properties

Dynamic models of molecular networks and pathways enable in silico evaluations of the consistency of proposed interactions and the outcomes of perturbations as well as of hypotheses on system-level structure and function. We postulate a continuous model of the activation dynamics of the ETHYLENE RESPONSE FACTOR 1 (ERF1) gene in response to ethylene signaling. This activation elicits the response of the PLANT DEFENSIN 1 (PDF1) gene, which also responds to jasmonic acid, and the inhibition of the PUTATIVE AUXIN RESPONSIVE FACTOR 2 (ARF2) gene, that also responds to auxin. Our model allows the effect of different ethylene concentrations in eliciting contrasting genetic and phenotypic responses to be evaluated and seems to consider key components of the ethylene pathway because the ERF1 dose-response curve that we predict has the same qualitative form as the phenotypic dose-response curves obtained experimentally. Therefore, our model suggests that the phenotypic dose-response curves obtained experimentally could be due, at least in part, to ERF1 changes to different ethylene concentrations. Stability analyses show that the model’s results are robust to parameter estimates. Of interest is that our model predicts that the ethylene pathway may filter stochastic and rapid chaotic fluctuations in ethylene availability. This novel approach may be applied to any cellular signaling and response pathway in plants and animals.