Fluctuation Resonance of Different Genetic Feed Forward Loops

The feed forward loop (FFL) is one of the most important "network motifs" in gene networks. Here we have numerically studied the response of eight genetic FFLs to external oscillatory signals. We find that, for the first gene X, the pure fluctuation resonance (FR) occurs at 2ω₀. For the second gene Y, the FR curves have some, but little difference between the positive and negative regulation types of Y by X. The FR curves of the third gene Z have different cases according to the FFL types, coherent or incoherent, with single peak of low frequency in coherent types or double peaks of low and medium frequency in incoherent types. The results show that the FFL types have much effect on the signal transduction of gene networks.