Fig. 2

Blue light activated systems. a NFAT/Melanopsin system utilizes blue light. The cascade of signaling events opens TRPC to allow calcium ion influx, which, in turn, activates calcineurin that dephosphorylates NFAT and allows for its translocation into the nucleus and the expression of the transgene. b CIB/CRY2 systems are activated by blue light and deactivated by darkness. The figure shows how CRY2/CIB1 was used to induce activation of split Cre recombinase by reconstituting the enzyme through its dimerization. Cre is a site-specific recombinase that catalyzes the recombination between two LoxP to excise sequence between them. Cre enzyme was split into two parts: the N-terminal fragment of Cre fused to CRY2 and the C-terminal fragment of Cre fused to CIB1. Blue-light induced interaction between CRY2 and CIB1 lead to the reconstitution of Cre, which then catalyzes recombination at loxP sites. c In the absence of blue light, the split transcription FKF/GI factor Gal4 is inactive. In the presence of blue light, VP16 links an active domain to the binding domain region of a transcription factor Gal4 that regains its function and enables expression of the gene of interest. TRPC transient receptor protein channels; Gaq Gaq-type G protein; PLC phospholipase C; PKC protein kinase C; NFAT nuclear factor of activated T-cells; CRY2 Cryptochrome 2; CIB CRY2-interacting bHLH; CreC; Pol II polymerase II; goi gene of interest; FKF1 Flavin-binding Kelch repeat F-box; VP16 activation domain of transcription factor VP16; GI GIGANTEA protein; DBD DNA binding domain