9708540 Purugganan The MADS-box regulatory gene family represents a group of genes that control crucial aspects of flower development. The molecular evolutionary dynamics of these developmental control genes remain poorly understood. This project seeks to investigate the molecular evolution of members of this regulatory gene family in the Hawaiian silversword alliance (Madiinae, Asteraceae), the premier example of island plant adaptive radiation. Three floral control genes - APETALA1, APETALA3 and AGAMOUS - will be isolated by molecular techniques in 14 silversword alliance species and their mainland California relatives, the tarweeds. Analysis of these gene sequences will be used to infer the rates and patterns of gene evolution in these rapidly-evolving taxa, and will provide information on the evolutionary forces that shape the diversification of these regulatory loci. This study will assess the dynamics of change in floral homeotic genes associated with a recent adaptive diversification, and may lead to the development of new nuclear markers for use in sequence-based, plant phylogenetic studies at low taxonomic levels. Determining mode and tempo of regulatory gene evolution is vital to understanding the genetic basis behind differences in morphologies between species. Studying these genes in the context of a well-studied adaptive radiation permits a greater knowledge of how genes that control developmental traits evolve in rapidly diversifying species. By dissecting the mechanisms behind the evolution of these control genes, it may be possible to determine the extent to which changes in gene regulation contribute to the diversity in floral structures we see in the natural world.
