Organ formation in Drosophila: specification and morphogenesis of the salivary gland

The Drosophila salivary gland has emerged as an outstanding model system fo r the process of organ formation. Many of the component steps, from initial regional specification through cell specialization and morphogenesis, are known and many of the genes required for these different processes have bee n identified. The salivary gland is a relatively simple organ; the entire g land comprises of only two major cell types, which derive from a single con tiguous primordium. Salivary cells cease dividing once they are specified, and organ growth is achieved simply by an increase in size of individual ce lls, thus eliminating concerns about the potential unequal distribution of determinants during mitosis. Drosophila salivary glands form by the same ce llular mechanisms as organs in higher organisms, including regulated cell s hape changes, cell intercalation and directed cell migration. Thus, learnin g how these events are coordinated for tissue morphogenesis in an organism for which the genetic and molecular tools are unsurpassed should provide ex cellent paradigms for dissecting related processes in the more intricate or gans of more complicated species. (C) 2001 John Wiley & Sons, Inc.