Profile and Department: Professor, Cell & Systems Biology, University of Toronto
A small group of pluripotent stem cells in the shoot meristem is the ultimate source for all aerial parts in higher; plants: the shoot axis, side branches, leaves and fowers. Genetic analysis, in Arabidopsis has identified a myriad of genes that converge to control the juvenile to adult leaf transitions and the switch of the vegetative meristem to reproductive development. However, unlike flowers and leaves, which form from a shoot apical meristem, embryonic leaves, or cotyledons, are formed separately from the shoot meristem during embryogenesis. Though genetic analysis we have determined that the two terpenoid hormones, gibberellin (GA) and abscisic acid (ABA), play important roles in the patterning of embryonic leaves. More importantly, manipulation of these hormone levels can result in the replacement of embryonic leaves with adult leaves indicating that although these organs have different spatial origins they are developmentally related. We are interested in how ABA and GA can do this and in the developmental relationship of embryonic and vegetative foliar organs. Aside from using the standard molecular approaches to address these problems we have also developed a chemical genetics program to identify new plant hormones that may play roles in embryonic and cotyledon development.