Growing up is never easy, but with discrete developmental stages to be successfully completed, growing up fly-style is far more risky. Fly larvae embark upon a developmental program where they progress through instars,triggered by ecdysteroid hormones and regulated by transcription factors,before pupating. But Lynn Riddiford and her team at the University of Washington discovered that if one of the ecdysteroid hormone regulated transcription factors BR-Z3, known as Broad, was inadvertently activated, the larvae failed to moult, bypassing the usual moulting program, and progressing directly on to the insect's final right of passage: pupation. Intrigued by this unusual departure from the insect's developmental program, Xiaofeng Zhou began investigating Drosophila, where he could activate BR-Z3 and related transcription factors at will. Watching the flies altered developmental progress, he discovered that misexpression of Broad transcription factors blocks the surge of ecdysteroid hormones that insects need to initiate moulting. Instead the insects continued growing until they reached their critical weight, when they begin pupating despite having missed their final instar ().
