Does the ocs-element occur as a functional component of the promoters of plant genes?
The structural requirements of the ocs-element, a promoter element in several genes transferred to the host plant nucleus by Agrobacterium tumefaciens and certain DNA viruses, have been further characterized both in vitro and in vivo. Two adjacent and functionally identical protein-binding sites separated by an exact number of nucleotides are required for in vivo activity of the ocs-element. Plant pathogens have presumably recruited cellular transcription factors that interact with these binding sites to drive the high-level expression of their essential genes. Our functional analyses of the ocs-elements from two pathogen promoters define the structure of a sequence motif that might also be expected to occur in plant nuclear genes, and a search of the plant gene database has identified a number of plant gene promoters that contain sequences that resemble the ocs-element. These sequences were analysed for their ability both to bind the maize nuclear protein OCSTF and to activate transcr
