One evolutionary theme that can be derived from the field of molecular developmental genetics is that diversity in morphology among species is achieved with a remarkably similar set of regulatory proteins. In the context of this similarity, current models suggest that diversity results from precise alterations in the functions of developmental regulatory genes. However, the molecular mechanisms underlying evolutionary changes in gene function are poorly understood, and they are difficult to derive from comparisons of divergent species because divergent species are the product of a large number of changes. In contrast, comparisons between closely related species may provide a sufficiently similar genetic and developmental background for the mechanism responsible for a specific change to be studied. In the nematode Caenorhabditis elegans, the lin-48 gene encodes a zinc finger transcription factor. lin-48 is important in the development of hindgut (rectum) cells and the excretory duct cell, and is expressed in these cells. Expression of C. elegans lin-48 transgenes is conserved when they are introduced into the closely related species C. briggsae, except the excretory duct expression is absent. This project will investigate regulation of lin-48 as a model for a precise change in a gene's specificity. A first objective is to identify the source of this change by functionally comparing regulatory elements from the promoters of C. elegans and C. briggsae lin-48 genes. A second objective is to investigate changes in lin-48 function between the two species. In C. elegans, lin-48 functions redundantly with other genes in the development of the excretory duct cell. Accordingly, the hypothesis that C. briggsae excretory duct development has shifted to rely on the function of one of these redundant genes will be tested. Graduate student mentoring will be integrated into these first two objectives. A third objective is to survey other Caenorhabditis zinc finger genes for differences in expression pattern between species. This objective will be carried out as part of an undergraduate research program. A fourth objective is to increase problem solving opportunities, peer tutorials, and active learning in a molecular genetics course for non-majors to encourage an interest in, and understanding of, genetics among non-specialists.
