Molecular interactions between the components of the En-I transposable element system of Zea mays

Abstract
The sequence of the Inhibitor element Spm‐I8 isolated from the wx‐m8 allele has been determined. The element is 2242 bp in length. Its ends can be folded into long stem and loop structures. In a line containing the autonomous En element (wx‐m8+En) we have detected a 2.5‐kb transcript hybridizing to Spm‐I8. A cDNA copy of this En‐specific transcript containing 1.2 kb of the 3′ end was cloned and its DNA sequence was determined. The 3′ half of the cDNA is homologous to Spm‐I8 and the region of homology is interrupted by intervening sequences. In the absence of an autonomous En element two chimeric transcripts are observed in the wx‐m8 line which are probably initiated at the wx promoter and terminate in the Spm‐I8 insertion. In the presence of the En element, these transcripts are suppressed, possibly by a trans‐acting function of En, inhibiting transcription read‐through into Spm‐I8.