Spatial and temporal control of expression with light-gated LOV-LexA

The ability to drive expression of exogenous genes in different tissues and cell types, under control of specific enhancers, has been crucial for discovery in biology. While many enhancers drive expression broadly, several genetic tricks were developed to obtain access to isolated cell types. Studies of spatially organized neuropiles in the central nervous system of insects have raised the need for a system that targets subsets of cells within a single neuron type, a feat currently dependent on stochastic flip-out methods. To access the same subsets of cells within a given expression pattern consistently across fruit flies, we developed the light-gated expression system LOV-LexA. We combined the bacterial LexA transcription factor with the plant-derived light oxygen voltage (LOV) photosensitive domain and a fluorescent protein. Exposure to blue light uncages a nuclear localizing signal in the C-terminal of the LOV domain, and leads to translocation of LOV-LexA to the nucleus, with subsequent initiation of transcription. LOV-LexA enables spatial and temporal control of expression of transgenes under LexAop sequences in larval fat body as well as pupal and adult neurons with blue light. The LOV-LexA tool is ready to use with GAL4 and Split-GAL4 drivers in its current form, and constitutes another layer of intersectional genetics, that provides light-controlled genetic access to specific subsets of cells across flies.