An assessment of morphological and molecular conservation of floral development between Arabidopsis thaliana and Theobroma cacao

by Swanson, John-David.

iii Comparative anatomical and developmental studies on Theobroma cacao L. flower development were conducted to provide insight into the general mechanisms that control floral development. These studies were also conducted to assess the level of conservation of these systems among plant species, especially with reference to Arabidopsis thaliana. To this end, we underwent a study to compare “normal” flowers of T. cacao to what is already known in model species. To provide complementary approaches to the same set of questions, we examined T. cacao floral development at the morphological, genetic and gene expression levels. Morphological comparisons were made though the analysis of time-lapse photography and light and electron microscopy to create mathematical models of flower development for T. cacao. At the genetic level, we compared EST sequence data from Arabidopsis, poplar, cotton and T. cacao through phylogenetic methods. To precisely localize gene expression patterns during T. cacao flower development, we performed in situ hybridizations using the floral integrator LEAFY as a probe, as well as several ABC genes. Comparison of the T. cacao floral developmental program with that of Arabidopsis revealed that although the final sizes and morphologies of flowers in the two species differ, their developmental programs are strikingly similar both morphologically and genetically. Consistent with this analysis, a cross-species analysis of the current knowledge in this field indicates a high degree of conservation kingdom wide.