Research

The structure, organization and radiation of Sadhu non-long terminal repeat retroelements in Arabidopsis species

Sanjida H Rangwala^1,2 and Eric J Richards^1,3

¹  Department of Biology, Washington University in St Louis, St Louis, MO, USA

²  Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, PA, USA

³  Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, NY, USA

author email corresponding author email

Mobile DNA 2010, 1:10doi:10.1186/1759-8753-1-10

Published:	1 March 2010

Abstract

Background

Sadhu elements are non-autonomous retroposons first recognized in Arabidopsis thaliana. There is a wide degree of divergence among different elements, suggesting that these sequences are ancient in origin. Here we report the results of several lines of investigation into the genomic organization and evolutionary history of this element family.

Results

We present a classification scheme for Sadhu elements in A. thaliana, describing derivative elements related to the full-length elements we reported previously. We characterized Sadhu5 elements in a set of A. thaliana strains in order to trace the history of radiation in this subfamily. Sequences surrounding the target sites of different Sadhu insertions are consistent with mobilization by LINE retroelements. Finally, we identified Sadhu elements grouping into distinct subfamilies in two related species, Arabidopsis arenosa and Arabidopsis lyrata.

Conclusions

Our analyses suggest that the Sadhu retroelement family has undergone target primed reverse transcription-driven retrotransposition during the divergence of different A. thaliana strains. In addition, Sadhu elements can be found at moderate copy number in three distinct Arabidopsis species, indicating that the evolutionary history of these sequences can be traced back at least several millions of years.