A MODIFIED AUTONOMOUS EN TRANSPOSON IN MAIZE (ZEA-MAYS L.) ELICITS A DIFFERENTIAL RESPONSE OF REPORTER ALLELES

Transposable elements in maize are composed of a defined molecular str ucture that includes coding sequences, determiners of functionality an d ordered terminal motifs that provide binding sites for transposase p roteins. Alterations in these components change the phenotypic express ion of unstable genes with transposon inserts. The molecular basis for the altered timing and frequency of transposition as determined by th e size and number of spots on kernels or stripes on leaves has general ly been described for defective inserts in genes. Most differential pa tterns can be ascribed to alterations in the terminal motifs of the re porter allele structure that supplies a substrate (terminal inverted r epeat motifs) for transposase activity. For autonomously functioning a lleles, the explanations for changes in phenotype are not so clear. In this report, an En-related element identified as F-En is described th at shares with En the recognition of a specific defective element c1(m r)888104 but differs from En in that this F-En clement does not recogn ize the canonical c1(mr) elements that are recognized by En. Evidence is provided suggesting that F-En does not recognize other En/Spm-relat ed defective elements, some of whose sequences are known. This modifie d En arose from a c1-m autonomously mutating En allele.