Factors determining chromosomal localization of transposable elements in plants

Abstract

Transposable elements (TEs) constitute a significant part of plant genomes and shape their genomic landscape. While some TEs are ubiquitously dispersed, other elements specifically occupy discrete genomic loci. The evolutionary forces behind the chromosomal localization of TEs are poorly understood. Therefore, we first review specific chromosomal niches where TEs are often localized including (i) centromeres, (ii) (sub)telomeres, (iii) genes, and (iv) sex chromosomes. In the second part of this review, we focus on the processes standing behind non-equal distribution of various TEs in genomes including (i) purifying selection, (ii) insertion site preference or targeting of TEs, (iii) post-insertion ectopic recombination between TEs, and (iv) spatiotemporal regulation of TE jumping. Using the combination of the above processes, we explain the distribution of TEs on sex chromosomes. We also describe the phenomena of mutual nesting of TEs, epigenetic mark silencing in TEs, and TE interactions in the 3D interphase nucleus concerning TE localization. We summarize the functional consequences of TE distribution and relate them to cell functioning and genome evolution.