Capture of a genomic HMG domain sequence by the En/Spm-related transposable element Tpn1 in the Japanese morning glory

The non-autonomous transposable element Tpn1 from the Japanese morning glory is an En/Spm-related DNA element found in the second intron of the DFR-B gene for flower pigmentation in the mutable line flecked, which shows variegation for flower color. It carries a genomic DNA segment containing at least four exon sequences encoding part of a HMG-box sequence. Spliced hybrid transcripts containing the DFR-B exon(s) and the HMG exons in Tpn1 were detected in the flower buds of the flecked line, and they were polyadenylated within Tpn1. Thus, Tpn1 can be regarded as a specialized transducing transposon carrying a part of the genomic sequence for a HMG box. The possible implications of the finding for evolution are discussed.