Fig. 2. Controlling expression through buffer gates and recombinase-based circuits.

Successful engineering of plant form will require fine control over gene expression, both in terms of magnitude and spatial patterning. a Circuits implementing buffer gates to tune expression of slr-1 (inhibits lateral root formation), allowed Brophy et al. to control the number of lateral roots formed. b Guiziou et al. utilized a serine integrase to create a circuit that permanently switches its output when the integrase is expressed, creating a form of cellular memory that records past gene activity.