Impact of transposable elements on polyploid plant genomes

Transposable elements (TEs), together with polyploidization have a key role in plant evolution, generating changes in genome size, as well as acting as a source for new coding and regulatory genetic sequences. Vicient and Casacuberta review the main consequences of TE activity in plant genomes and gene evolution, in particular after polyploidization events.

The close connections of polyploidization and TE dynamics. Polyploidization is accompanied by a release of TE silencing, which may be different for parentally or maternally inherited TEs. This release, in addition to activating TE mobilization, may induce changes in the regulation of genes located near TEs. The burst of TEs will produce new TE insertions that can modify the coding capacity of genes or their regulation. The release of TE silencing is reversed after few generations, and TE sequences again become the target of epigenetic silencing mechanisms. The silencing of TEs, including the new insertions resulting from the TE burst, will influence the expression of genes located nearby. This may result in changes of gene expression with respect to the early phases of polyploidy but also with respect to the diploid parents. TEs will also be important for the diploidization of the polyploid genome, as the different TE copies may provide sequence homology for recombination, leading to deletions and chromosome rearrangements.

Over a short period, polyploidization tends to induce bursts of transposition, probably due to a relaxation in the genome’s epigenetic control. Over longer intervals, TE bursts may induce global changes in genome structure, including losses of large genome regions and chromosomal rearrangements.

This paper is part of the Annals of Botany Special Issue on Polyploidy in Ecology and Evolution. It will be free access until October 2017, then available only to subscribers until August 2018 when it will be free access again.