Recent research has shown clearly that animal morphological evolution has depended in important ways on the reutilization of genetic regulatory pathways in different species. Much of what is known about the regulation of development has depended on a limited number of genetic model species, such as Drosophila (the fruit fly), Caenorhabditis (the worm), and zebrafish. In some ways, however, development is too divergent in these organisms to understand in detail how genetic changes have been important to evolution. Recently the red flour beetle, Tribolium castaneum, has emerged as a second powerful insect genetic model system. Although fly and beetle morphology are variations of a common theme, in many ways beetle development is much more typical of other insects, while that of Drosophila is highly specialized. Thus, comparisons of these and other insect species can and has given insight into changes in genetic mechanisms underlying morphological evolution.
The current research is focused on the genetic regulatory mechanisms underlying the establishment of antennal identity. The mechanisms for adult development in Drosophila are well described, but (because of the highly specialized morphology of the fly larva) those for larval development are much more poorly characterized. Because of the much more typical morphology of the beetle larval antenna, studies of the regulation of beetle antennal development will illuminate mechanisms in more typical insects and show how these mechanisms have changed during evolution of the flies. Firstly, the roles of genes known to be important to the establishment of antennal identity in Drosophila will be explored in Tribolium by examining when and where they are active as well as the consequences of interfering with their developmental effects. Secondly, the power of genetic analysis possible with Tribolium (unparalleled among arthropods other than Drosophila and its close relatives) will be used to identify by mutation other important genes not predicted from Drosophila studies. This approach will provide key information on the evolution of genetic regulatory mechanisms as well as demonstrate that a mutational approach to understanding development is possible in an insect other than Drosophila.
The proposed work has excellent potential to provide a model relevant to a general understanding of the genetic basis of morphological evolution. Moreover, the work will further support the utility of Tribolium as an insect genetic model system. The participants have freely shared genetic and molecular materials, as well as techniques, in the past, and will continue to do so. (This is an expectation of all researchers, but is especially important in an emerging system like Tribolium.) Likewise, although not primarily supported by NSF, support will contribute to a large transposon mutagenesis project from which insertion lines are publicly available, and to the improvement of BeetleBase, a site devoted to Tribolium molecular and genetic data. These are major resources for the Tribolium community. Further, the participating laboratories have an outstanding record of incorporating undergraduates in research. Although not all undergraduates have generated a publishable body of work, six undergraduates have authored eight papers. Undergraduate researchers will continue to participate in this NSF-funded study.
