An unusual transposon encoding heat shock inducible and developmentally regulated transcripts in Dictyostelium

We have isolated and characterized a transposable element from Dictyostelium discoideum denoted Tdd-1. There are ∼50 complete copies of the element per haploid genome and ∼100–150 partial elements. Southern blots of DNA from different Dictyostelium discoideum strains show that Tdd-1 is a mobile element. Tdd-1 is 4.9 kb long, with 313 bp inverted repeats. These repeats lie near the termini, but unlike other transposable elements one end of Tdd-1 extends 36 bp past the repeat and the other extends 1 bp. Tdd-1 encodes a series of developmentally regulated transcripts, all with the same polarity, that increase dramatically in abundance after ∼10 hr of development. We have also identified a heat shock inducible transcript of the opposite polarity.