Transposons Continue the Amaze

Abstract

Transposable elements (TEs) were first discovered in maize plants. However, they exist almost in all species with a few exceptions (Plasmodium falciparum, Ashbya gossypii and Kluveromuyces lactis). They are the most important contributors to genome plasticity and evolution and even epigenetic genome regulation. Organisms with large genomes have high transposon percentages. For example, Arabidopsis thaliana has a genome size of 125 Mb which comprises 14% transposons, Homo sapiens (3000 Mb) 45-48.5%, and Hordeum vulgare genome (5300 Mb) has 80%. TEs are classified into two major groups based on their transposition mechanisms: Class I (RNA transposonsretrotransposons) and Class II (DNA transposons). Recent progress in whole-genome sequencing and long-read assembly have resulted in identification of unprecedentedly long transposable units spanning dozens or even hundreds of kilobases, initially in prokaryotic and more recently in eukaryotic systems. All TEs in a cell are named as transposome (mobilome), and transposomics is a new area to work with transposome. Although a number of bioinformatics softwares have recently been developed for the annotation of TEs in sequenced genomes, there are very few computational tools strictly dedicated to the identification of active TEs using genome-wide approaches. In this review article, after a brief introduction and review of the transposable elements, I discussed their effects in gene expression, evolution, recent applications and also share our research on retrotransposons with different organisms.