Let there be multifunctionality: Uncovering the dynamical zoo of the AC-DC genetic circuit

Gene regulatory networks (GRNs) govern many cell processes. While multistability and oscillations are common GRN dynamics, they are typically studied and engineered in isolation. Here, we challenge this separation using the AC-DC circuit, a minimal three-gene network that merges the classical toggle switch and repressilator. Using a thermodynamic formalism and Bayesian inference, we show that a single-inducer version of the circuit displays diverse multifunctional dynamics, including coexistence of oscillations and multistability. We explore robustness, classify emergent behaviors, and analyze critical slowing down. Remarkably, the AC-DC circuit can produce more than thirty topologically distinct bifurcation diagrams, results that challenge the classical view that network topology rigidly constrains dynamical outcomes. This flexibility enables synthetic capabilities coupling hysteresis with oscillations, criticality, and reversibility. By uncovering the potential of minimal genetic circuits and outlining design principles for their implementation, this work opens directions for harnessing emergent complexity using the basic building blocks of life. A record of this paper's transparent peer review process is included in the supplemental information.