The ocs-element is a component of the promoters of several T-DNA and plant viral genes

Abstract

The ocs-element is an enhancer element first identified in the promoter of the octopine synthase gene (OCS) where it occurs as a 16 bp palindromic sequence. The transcriptional enhancing activity of the ocs-element correlated with in vitro binding of a transcription factor. We have now identified ocs-elements in the promoter regions of six other T-DNA genes involved in opine synthesis and three plant viral promoters including the 35S promoter of cauliflower mosaic virus. These elements bind the ocs transcription factor in vitro and enhance transcription in plant cells. Comparison of the sequences of these 10 elements has defined a 20 bp consensus sequence, TGACG(T/C)AAG(C/G)(G/A)(A/C)T(G/T)ACG(T/C)(A/C)(A/C), which includes the 16 bp palindrome in its central region. We propose the name ocs-element for this class of promoter elements of similar sequence and function.