Figure 2. Optogenetic control to reverse engineer embryonic processes.

(A) Light inducible systems adapted to embryonic tissues can be utilized to manipulate the localization or activation of receptors, signaling molecules and enzymes in whole organisms. (B) OptoSOS translocates to the membrane under blue-light induction, activating Ras-Erk signaling. In Drosophila, a set of rules determines the outcome for light activated Erk: extended activation initiates gastrulation, whereas transient activation at dorsal regions defines the neuroectoderm. At anterior regions, head structure formation requires both Erk stimulation and Bicoid expression. (C) Light induced aggregation of membrane bound Cry2-Delta leads to Notch/Delta interaction in neighboring cells. In ectodermal tissues, activation of optoDelta defines two populations of cells, thus defining tissue boundaries. (D) Light-dependent membrane recruitment of the phosphatase OCRL (5ptase) leads to dephosphorylation of phosphatidylinositol-diphosphate (PIP₂) to a monophosphorylated PIP. The alteration in membrane composition prevents the cytoskeletal changes required for invagination of the tissue. Light activation of OCRL in restricted embryonic regions prevents the local invagination of the tissue.