Evolution of Genetic Mechanisms Controlling Developmental Fate

Kansas State University, Manhattan KS

Investigators

Abstract

0321882 Denell The intellectual merit of the proposed activity. Studies of the fruit fly, Drosophila melanogaster, have shown that embryonic developmental commitments along most of the anterior-posterior axis are controlled by homeotic genes in two Hox clusters: the Antennapedia complex (ANTC) and bithorax complex (BXC). Comparative molecular studies indicate that a single Hox complex (the equivalent of the ANTC and BXC in juxtaposition) arose very early in animal evolution, and that the genes in such complexes play important roles in regulating developmental commitments throughout the kingdom. A good deal of interest has been stimulated by the hypothesis that changes in Hox gene functions have been an important aspect of morphological evolution. The P.I./co-P.I.s have been developing Tribolium as a second insect genetic model system, which allows meaningful comparisons with Drosophila and other insects. To date over 100 mutations in the Tribolium Hox complex have been isolated. All of the Hox genes have been cloned, and their structure and expression pattern described. These researchers have also shown that a construct based on the lepidopteran transposable element piggyBac can be used for facile germ line transformation, that insertion lines can be easily and stably maintained by selection, and that stable insertions can be remobilized in a fashion which will allow enhancer trapping and mutagenesis by transposon tagging. These techniques provide a very strong rationale for the continued study in Tribolium of the control of developmental decisions and the implications for morphological evolution. Proposed studies include the completion of work in progress and the undertaking of new, transposon-based approaches. Characterization of EMS-induced variants, isolated because they fail to complement one of two deficiencies that overlap in the region of the Hox complex, will be completed. A study of genes specifying antennal fate by characterizing the cloned homothorax and extradenticle genes and by cloning and studying the spineless ortholog will also be completed. A major goal of the next grant period will be to undertake genome-wide transposon mutagenesis by remobilizing an insertion. This approach will allow the recognition of new variants in the Hox complex, as well as the isolation, easy maintenance, and cloning of developmentally significant mutations throughout the genome, and the isolation and characterization of useful enhancers. The roles of Tribolium Hox genes will be studied further by ectopically expressing them as transgenes. The broader impacts resulting from the proposed activity. The proposed work will have a broader impact in several ways. Firstly, the laboratories participating in this proposal have an outstanding record of incorporating undergraduates in research. We intend to continue to incorporate outstanding undergraduates into our research program, with special attention on recruiting female and minority students. Secondly, in addition to working toward answering specific experimental questions, we will continue to develop Tribolium castaneum as a model system for a variety of studies that involve a genetic as well as molecular component. We have freely shared materials and techniques in the past, and will do so in the future.