Vicillin (or 7S) seed storage protein genes are expressed specifically in the apical and central regions (cotyledons, shoot apical meristem and hypocotyl) of dicot plant embryos after the periods of cell division and morphogenesis. THey are good markers for the late stage of cotyledon maturation. Necessary and sufficient information for apical expression in transgenic tobacco embryos is contained within a fragment of DNA (UAS1, -295 to -109) from a bean 7S gene (B-phaseolin). We have used electrophoretic mobility shift assays and methylation interference to identify UAS1 nucleotide motifs which are directly contacted by bean nuclear protein(s) in vitro. In order to understand how the UAS2 element regulates gene activation during development we are cloning cDNA sequences that code for UAS1 binding proteins. We will complete cloning of cDNA sequences coding for bean nuclear protein(s) that bind to the Vb1 and Vb2 segments of the seed-specific enhancer. We will also study the interactions between individual protein factors and their target sites on the DNA and how they affect spatial regulation of gene transcription in tobacco plants. %%% The rational design of improved agricultural crops regquires targeting novel gene activities to specific plant tissues and organs. In order to accomplish that economically important goal, a thorough understanding of the factors that regulate plant development must be achieved. These studies on the interaction between specific DNA sequences and nuclear regulatory proteins leading to developmentally controlled and tissue specific gene expression will enhance our understanding of those mechanisms.
