Sensitivity of the timing of Drosophila pupal wing morphogenesis to external perturbations

The morphogenesis of the pupal wing of Drosophila melanogaster is a powerful model for understanding the physical mechanisms of tissue morphogenesis. During this process, the wing undergoes a dramatic reshaping where the hinge region contracts and pulls on the blade region, triggering a dynamic pattern of cell elongation changes, cell divisions, and cell neighborhood changes Etournay et al. (2015). Over our several year study of this process, we noticed that sometime after the year 2016, the onset of morphogenesis became consistently delayed by [~]6 h compared to previous years. Thus, the peak of cell elongation was now observed at 28 hours after puparium formation (hAPF) rather than at 20-22 hAPF. We show here that this delay is independent of genetic background and that the speed of the overall process is relatively unchanged, implying that an environmental factor causes a shift in the onset of the process relative to the start of pupariation. We then investigated how various environmental factors influence the timing of pupal wing morphogenesis, using the dynamics of cell elongation as a proxy. We find that imaging conditions, temperature, diet, Wolbachia infection, and the light/dark cycle have relatively little effect. Preliminary data show that the spectra of light used to rear the flies affects cell elongation dynamics, although the delay was not completely reverted and more experiments are needed to know precisely how this variable affects morphogenesis. In sum, our work suggests the presence of a gate controlling the onset of pupal wing morphogenesis that is influenced by a specific, yet unclear, environmental factor. Once the gate is released, pupal wing morphogenesis occurs at a fairly constant rate, remarkably robust to many environmental variables.