AUTHOR=Huang Jianhua , Wang Yushuai , Liu Wenwen , Shen Xu , Fan Qiang , Jian Shuguang , Tang Tian 

TITLE=EARE-1, a Transcriptionally Active Ty1/Copia-Like Retrotransposon Has Colonized the Genome of Excoecaria agallocha through Horizontal Transfer

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.00045

DOI=10.3389/fpls.2017.00045

ISSN=1664-462X

ABSTRACT=<p>Long terminal repeat (LTR) retrotransposons constitute the majority of the content of angiosperm genomes, but their evolutionary dynamics remain poorly understood. Here, we report the isolation and characterization of a putative full-length (~9550 bp) Ty1/<italic>copia</italic>-like retrotransposon in <italic>Excoecaria agallocha</italic> and its evolution in Euphorbiaceae. The so-called <italic>EARE-1</italic> is phylogenetically closely related to <italic>RIRE-1</italic> from <italic>Oryza australiensis</italic>, and has proliferated recently (~7.19 Mya) in the <italic>E. agallocha</italic> genome. An RT-PCR analysis revealed substantial transcription of <italic>EARE-1</italic> in all examined organs (leaves, staminate flowers, pistillate flowers, seeds, and roots) in unstressed <italic>E. agallocha</italic> plants and indications of elevated expression under stress. We conducted sequence analyses of 256 RT-RH fragments (~860 bp) of <italic>EARE-1</italic> from 34 species representing four subfamilies of Euphorbiaceae that exist in China. <italic>EARE-1</italic> copies from two <italic>Excoecaria</italic> species and <italic>Phyllanthus urinaria</italic> showed incongruent phylogeny with the host species and exhibited high sequence similarity to the host genes, suggesting a horizontal transfer from <italic>P. urinaria</italic> to the common ancestor of <italic>Excoecaria</italic>. However, SSAP analysis detected no new insertions of <italic>EARE-1</italic> among full-sibling progeny plants of <italic>E. agallocha</italic>, despite considerable SSAP polymorphisms among half-siblings. <italic>EARE-1</italic> is the first transcriptionally active Ty1/<italic>copia</italic>-like retrotransposon isolated from <italic>E. agallocha</italic>. Our results provide empirical evidence of the horizontal transfer of LTR retrotransposons in plants, and may suggest a significant role of post-transcriptional host control in the life cycles of transposable elements.</p>