Stage-specific modulation of gene expression with muscle GAL4 promoters.

The bipartite GAL4/UAS system is the most widely used method for targeted gene expression in and facilitates rapid genetic experimentation. Defining precise gene expression patterns for tissues and/or cell types under GAL4 control will continue to evolve to suit experimental needs. However, the precise spatial and temporal expression patterns for some commonly used muscle tissue promoters are still unclear. This missing information limits the precise timing of experiments during development. Here, we focus on three muscle-enriched GAL4 drivers (-GAL4, -GAL4 and -GAL4) to better inform selection of the most appropriate muscle promoter for experimental needs. Specifically, -GAL4 and -GAL4 turn on in the first or second instar larval stages, respectively, and can be used to bypass myogenesis for studies of muscle function after development.