Receptor tyrosine kinases (RTKs) are members of a superfamily of surface receptors consisting of 20 subfamilies that transmit environmental signaling cues into cells.¹  Binding of signaling cues (i.e. ligands) to RTKs usually results in dimerization and leads to the activation of signals through auto-phosphorylation and phosphorylation of downstream substrates. This dimerization-dependent activation led to the idea of synthetic regulation of RTKs using chemical dimerizers. However, recent developments in optogenetic actuators, especially light-responsive, homo-interacting proteins such as the PHR domain of cryptochrome 2 (CRY2) from Arabidopsis thaliana (PHR hereafter) and light-, oxygen- and voltage-sensing (LOV) domains, have established light as the inducer and the activator of signaling molecules.²