Modification of the ABC Program and the Evolution of Floral Novelty

Harvard University, Cambridge MA

Investigators

Abstract

Kramer 0319103 Understanding how new morphological characters evolve has become a major focus of the rapidly growing field of comparative developmental genetics. In flowering plants, it has been proposed that radical changes in floral morphology may have been mediated by simple shifts in the expression domains of homeotic floral organ identity genes. This hypothesis has not been carefully tested, however, and still leaves unexplained the question of how the underlying program may have been modified in cases where a simple "sliding boundary" model is insufficient to explain morphology. These issues can be addressed through studies of the lower eudicot family Ranunculaceae, which contains a great diversity of floral morphology. Although preliminary data suggest that the ABC program in this family has been reshaped by gene duplications, further characterization of ABC gene homologs is necessary to clarify these findings and test their broader applicability. To these ends, the objectives of the project are: 1) to analyze the expression patterns of AP3, PI, AG, and AP1 homologs in Aquilegia vulgaris using in situ hybridization; 2) to characterize homeotic mutants of A. vulgaris using SEM, gene expression studies, candidate gene sequencing and analysis of genetic segregation; 3) to determine the protein dimerization and DNA binding capabilities of AP3 and PI homologs from Aquilegia vulgaris; and 4) to use antibody localization to determine the protein distribution of AP3, PI, AG and AP1 gene products in Aquilegia vulgaris, Xanthorhiza simplicissima, Clematis integrifolia, Clematis alpina and Ranunculus ficaria. In addition to investigating the evolution of floral morphology, these studies will address issues such as the conservation of organ identity gene function outside the core eudicots and the role of gene duplication in the evolution of novel developmental programs. In terms of broader impact, this project will provide training for undergraduate, graduate and postdoctoral students.