Evolutionary developmental genetic studies on morphological variations: Floral structures in Lepidium L. (Brassicaceae) and nectaries in eudicots

Rapid progress in developmental genetics and evolutionary biology has led to new approaches to address to one of the fundamental biological questions: how evolution acts on the gene and morphology.; The main goal of this dissertation research was to understand the nature of morphological variations in flowering plants using the current knowledge of gene functions and available methods. Two main developmental processes were studied: variations of floral structure in Lepidium (Brassicaceae) and the diversity of nectaries in core eudicots.; Phylogenetic analysis of Lepidium using nuclear marker, in this case sequences of the first intron of PISTILLATA, revealed that the diversification of floral structures in Lepidium was influenced by allopolyploid hybridization events. Analysis of floral structures of interspecific hybrids suggested that the allelic dominance of the reduced stamen numbers contributed to the propagation of species with reduced stamen numbers via allopolyploidization.; To understand the diverse nature of nectary development in eudicots two studies were performed. We analyzed the promoter of CRC, a key gene of nectary and carpel development in Arabidopsis, in a comparative approach. Functional analysis of conserved promoter regions in Arabidopsis and Lepidium, close relatives in Brassicaceae, showed that evolutionarily conserved regions include cis-regulatory elements required for the regulation of CRC. In conserved regions, putative binding sites of LEAFY and MADS-box proteins were identified and they were found to be significant for proper CRC expression in nectaries and carpels. Molecular genetic studies of nectary development and CRC suggested that CRC might be a general regulator for nectaries of diverse structure. Expression analyses of CRC in exemplary species with differing nectary positions and morphologies suggested that CRC might have been recruited as a general regulator of nectary development before the diversification of core eudicots whereas it might have evolved to establish carpel polarity in the evolution of angiosperms.