HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Supplemental Research Data All Versions of this Article: rna.916708v1 14/5/814    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Piriyapongsa, J. Articles by Jordan, I. K. PubMed PubMed Citation Articles by Piriyapongsa, J. Articles by Jordan, I. K. Social Bookmarking                   What's this?

Dual coding of siRNAs and miRNAs by plant transposable elements

School of Biology, Georgia Institute of Technology, Atlanta, Georgia 30332-0230, USA

We recently proposed a specific model whereby miRNAs encoded from short nonautonomous DNA-type TEs known as MITEs evolved from corresponding ancestral full-length (autonomous) elements that originally encoded short interfering (siRNAs). Our miRNA-origins model predicts that evolutionary intermediates may exist as TEs that encode both siRNAs and miRNAs, and we analyzed Arabidopsis thaliana and Oryza sativa (rice) genomic sequence and expression data to test this prediction. We found a number of examples of individual plant TE insertions that encode both siRNAs and miRNAs. We show evidence that these dual coding TEs can be expressed as readthrough transcripts from the intronic regions of spliced RNA messages. These TE transcripts can fold to form the hairpin (stem–loop) structures characteristic of miRNA genes along with longer double-stranded RNA regions that typically are processed as siRNAs. Taken together with a recent study showing Drosha independent processing of miRNAs from Drosophila introns, our results indicate that ancestral miRNAs could have evolved from TEs prior to the full elaboration of the miRNA biogenesis pathway. Later, as the specific miRNA biogenesis pathway evolved, and numerous other expressed inverted repeat regions came to be recognized by the miRNA processing endonucleases, the host gene-related regulatory functions of miRNAs emerged. In this way, host genomes were afforded an additional level of regulatory complexity as a by-product of TE defense mechanisms. The siRNA-to-miRNA evolutionary transition is representative of a number of other regulatory mechanisms that evolved to silence TEs and were later co-opted to serve as regulators of host gene expression.

Keywords: transposable elements; miRNA; siRNA; arabidopsis; rice

CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?