Dissection of imaginal discs in Drosophila.

INTRODUCTIONImaginal disc primordia appear in embryos as clusters of 20-40 cells that invaginate from the embryonic epithelium. Each disc is a single-layered epithelial sheet or sac that stays connected to the embryonic and larval epithelium by a thin stalk. Eventually, each sac flattens and the two sides of the sac take on different characteristics, forming on one side the thicker, highly folded disc epithelium and on the other side, the thinner, unfolded peripodial membrane. The imaginal discs are set aside during embryonic development and do not participate appreciably in larval life. However, the discs undergo extensive proliferation during the three larval instars, and by late in the third instar, just before metamorphosis, each disc contains tens of thousands of cells. During metamorphosis, the larval epidermis is converted into the pupal case, and the imaginal discs (along with the histoblast nests) form the outer covering of the developing adult. Most of the ectodermal adult structures are derived from the disc epithelium. This protocol describes methods for dissecting imaginal discs from Drosophila larvae.