The long term goals of Dr. An's work are to understand the regulatory mechanisms of gene expression and the molecular basis of differentiation using plants as a model system. He has been working on the nopaline synthesis (nos) promoter to identify cis- acting regulatory elements of the promoter and to study the functional role of these elements. He will continue to study the nos promoter to further define the sequence specificity of the regulatory elements and function of these elements. He will focus on the nos upstream regulatory region which consists of several cis-acting elements. These elements will be further defined by saturation mutagenesis. He proposes to isolate regulatory genes whose products specifically interact with the nos upstream region by screening a lambda phage expression library with the nos promoter fragment as a probe. He will also attempt to obtain regulatory mutants from Arabidopsis thaliana which fail to turn on the nos promoter during a specific stage of development. Although the nos promoter is small and originated from the Ti plasmid, the promoter consists of several interesting regulatory elements that respond to various developmental and environmental conditions of plant growth. %%% The information obtained from the study of this regulator of gene expression will serve as a useful model for understanding the structure and function of complex regulatory mechanisms of plants.
