The transposable element Enhancer (En/Spm) of Zea mays encodes the functions necessary for transposition of members of the En-I family of elements. En constructs were introduced into tobacco and transposition was demonstrated by cloning and DNA sequence analysis. Transcriptional analysis of En transgenic plants revealed 2.5 and 6 kb En homologous transcripts similar in size to those found in maize, in addition to aberrant splice products. Progeny analysis of a primary transformant indicates En transpositional activity after meiosis. In these progeny somatic variegation, at the NPT II gene, was demonstrated to be caused by En excision. Two re-insertions of En were analyzed and found to reside in unique copy DNA while another was found in middle repetitive DNA.