Mobilization of Stowaway-like MITEs in newly formed allohexaploid wheat species

Abstract

Transposable elements (TEs) dominate the genetic capacity of most eukaryotes, especially plants, where they can account for up to 90% of the genome, such as in wheat. The relationship between TEs and their hosts and the role of TEs in organismal biology are poorly understood. In this study, we have applied next generation sequencing, together with a transposon display technique in order to test whether a Stowaway-like MITE, termed Minos, transposes following allopolyploidization events in wheat. We have generated a 454-pyrosequencing database of Minos-specific amplicons (transposon display products) from a newly formed wheat allohexaploid and its parental lines and retrieved hundreds of novel MITE insertions in the allohexaploid. Clear mobilization of Minos was also seen by site-specific PCR analysis and sequence validation. In addition, using real-time qPCR analysis we observed an insignificant change in the relative quantity of Minos from the expected value of merging the two parental genomes, indicating that, despite its activation, no significant burst in Minos copy number can be seen in the newly formed allohexaploid. Interestingly, we found that CCGG sites surrounding Minos underwent massive hypermethylation following the allohexaploidization process. Our data suggest that MITEs have maintained their capacity for activity throughout the evolution of wheat and might be epigenetically deregulated in the first generations following allopolyploidization.