Discovery of a Zdel transposable element in Zea species as a consequence of a retrotransposon insertion

Nucleotide sequences similar to del1 retrotransposon from Lilium henryi have been discovered in Zea diploperennis as a consequence of finding a Zea retrotransposon element inserted into one of them. These sequences named Zdel (Zea del1-like) elements are present in all the Zea species (about 100 copies per haploid genome) and in Tripsacum dactyloides and absent from closely related genera. Sequences corresponding to gag and protease domains from a Zdel element have been identified. The Zdel protease sequence shows a conserved active site motif (DT/SG) from aspartic proteases. The high level of DNA methylation found in Zdel elements may be related to the observed absence of transcriptional activity.