Appendage morphology and numbers are the keys used to define arthropod subgroups and on that basis, insects are thought to have evolved from a myriapod-like animal which had identical limbs on each of many trunk segments. In a dipteran insect, Drosophila melanogaster, a gene named distal-less (Dll) is expressed in developing limbs. A homologue to that gene was cloned from Precis coenia, a lepidopteran insect. That gene is also expressed in all developing limbs, except the mandible, but in distinct patterns in different limb types. These results suggest that Dll could be a useful probe with which to examine the relationships between the appendages of different arthropods and to determine the origin of appendages in arthropod ancestors. Representative myriapod and crustacean species will be chosen. Homologues of Dll will be cloned from each species chosen and the expression pattern of these genes in developing embryos and appendages will be determined. %%% Although we have some understanding of how simple molecules might have evolved to more complex forms, there is complete mystery surrounding the evolution of complex structures such as limbs or wings. The results of this work should give insight on appendage (and arthropod) evolution and, perhaps, suggest mechanisms for the evolution of such structures. Review Analysis Form 7 BIR 9411213 Grace R. Panganiban Dr. Sean Carroll is striking out in a new direction in his interest in molecular evolution of appendage development. He is an outstanding scientist and this is an excellent environment for Dr. Panganiban to continue her studies in this area. She has been in his lab for 2 1/2 years, first working on a molecular study of neuroblast formation and then switching to this project. (She is tied to this area for personal reasons.) Her references were all positi ve and this is an exciting and novel area of research. The one panelist that was relatively lukewarm in his assessment of this proposal felt that "this proposal lacks a compelling evolutionary motivation" but his colleagues disagreed. Support is recommended.
