  Feed-forward dynamics, which is well-known to have several important
implications in nonlinear dynamical systems, frequently occurs in gene
expression motifs, and has been well explored experimentally and
mathematically. However, dependency of the components of a genetic circuit upon
its host, due to the requirement for resources like ribosome, ATP,
transcription factors, tRNA, etc., and related effects are of utmost
importance, which is commonly ignored in mathematical models. In a
resource-limited environment, two apparently unconnected genes can compete for
resources for their respective expression and may exhibit indirect regulatory
connection; an emergent response thus arises in the system completely because
of resource competition. In this work, we have shown how the responses of the
feed-forward loop (FFL), a well-studied regulatory genetic motif, can be
recreated considering the resource competition in a three-gene pathway.
Exploring the genetic system with temporal as well as spatiotemporal stability
analysis, interesting transient and steady-state responses have been observed.
The genetic motifs explored in this paper show many of the characteristic
features of the conventional FFL structure, like response delay and pulse
generation. Most interestingly, in a two-dimensional cellular arrangement,
characteristic pattern formation under a concentration gradient of input
signals have also been observed. This study pinpoints a larger area of research
and exploration in synthetic and cellular systems, which will reveal novel
controlling ideas and unique behavioral changes in the system for its context
dependencies.
