**6. Conclusions**

Optogenetics, is a new branch of synthetic biology, is generally defined as the engineering of particular light-induced cellular reactions. This study was initiated with light-sensitive Phytochromes and bacteriochromes experimented in bacteria and mammalian neurons. Recently this research field is sensational due to the CBCRs from cyanobacteria are widely used as signaling components. These CBCRs in optogenetic systems performed the regulation of cellular responses spatially and temporally by precisely applying and removing light. A cyanobacterial photoreceptor-based optogenetic system was implemented to study the protein interaction and cell signaling in cyanobacteria, bacteria and mammalian cells. The application of CBCRs in optogenetic systems extends their usage in developing potential new therapeutics. Smaller size photosensory regions and autocatalytic activity of CBCRs are more advantageous than other photoreceptors.
