In Vivo Footprinting Identifies an Activating Element of the Maize Adh2 Promoter Specific for Root and Vascular Tissues

In vivo footprinting identifies four putative cis elements of Adh2 that interact with protein factors within the DNase I hypersensitive domains of the 5' flanking region. The power of in vivo footprinting to identify functionally significant sites within a gene promoter was tested by biochemical and transgenic analyses of the putative element at position -160. Biochemical analyses show that proteins isolated from maize cell suspensions will bind to the Adh2 promoter in vitro to generate a footprint at -160 identical to that seen in vivo. The partially purified factor bound to the promoter in vitro can be specifically competed with fragments of DNA containing the element sequence, further demonstrating that a specific protein generates the footprint over that sequence. Transgenic analyses indicate that the -160 element is a functional element of the maize Adh2 promoter that acts as an activator in the meristem and vascular tissue of roots and in the vascular tissue of stems and leaves.