Imaginal discs: a unique evolutionary innovation
Fig 1. Leg development in Drosophila
In response to a pulse of the molting hormone ecdysone, each leg disc everts and elongates - the central portion of the disc becoming the distal part of the appendage - and through a series of tightly orchestrated events transforms itself into an adult leg. Surprisingly this process occurs in the absence of cell proliferation. One could say that at the end of the pupal stage, the adult leg is already “hidden” in the imaginal disc, waiting to be unfolded - like a reverse origami - at the appropriate developmental moment. Through studying the mechanisms that govern the transformation of a leg disc into an adult leg, Prof. Ohsawa is trying to answer universal questions concerning the folding and unfolding of an epithelial tissue in 3-dimensional space.