The last year or so has seen a flurry of reports on the control of growth and body size in Drosophila. A central theme to these papers is the idea of signaling between organs as a control mechanism for overall body growth and development (see for summary). This concept is obviously not new; decades of research on the growth hormone/insulin-like growth factor axis in mammals have emphasized the role of endocrine factors in body growth. But these fly studies now open up the possibility of using a genetically tractable system to dissect in detail how organ-to-organ communication dictates body size. For example, one obvious question that these papers leave unanswered concerns the nature of the relevant organ-to-organ signaling molecules. Undoubtedly, the versatility and sophistication of Drosophila genetics, and in particular the ability to perform targeted, tissue-specific loss-of-function RNAi screens, will spur research into the identification of these elusive factors. Once we discover these secreted factors, will we find that they are conserved, and might they play similar endocrine roles in other animals? Certainly, the insulin-like peptides present a strong precedent for conserved organ-to-organ signaling networks that control body growth and size. Nevertheless, even if the factors are not conserved, the principle of organ-to-organ signaling and physiology as governing mechanisms for body size control will probably be central to animal development. And no doubt Drosophila research will continue to lead the way in unraveling these mechanisms.
Signaling between different organs can influence overall growth and development in Drosophila larvae