A highly specific microRNA‐mediated mechanism silences LTR retrotransposons of strawberry. (January 2016)

• Record Type: Journal Article
• Authors: Šurbanovski, Nada; Brilli, Matteo; Moser, Mirko; Si‐Ammour, Azeddine
• Is Part Of: Plant journal. Volume 85:Number 1(2016:Jan.)
• Page Start: 70
• Page End: 82
• Publication Date: 2016-01
• Subjects: Degradome -- miRNA -- LTR retrotransposon -- primer binding site -- Fragaria vesca -- tRNA; Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.13090
• Languages: English
• ISSNs: 0960-7412

Abstract

Summary: Small RNAs are involved in a plethora of functions in plant genomes. In general, transcriptional gene silencing is mediated by 24‐nucleotide siRNAs and is required for maintaining transposable elements in a silenced state. However, microRNAs are not commonly associated with transposon silencing. In this study, we performed small RNA transcriptome and degradome analyses of the Rosaceae model plant Fragaria vesca (the woodland strawberry) at the genome‐wide level, and identified miRNA families and their targets. We report a highly specific mechanism of LTR retrotransposon silencing mediated by an abundant, ubiquitously expressed miRNA (fve–miR1511) generated from a single locus. This miRNA specifically targets LTR retroelements, silencing them post‐transcriptionally by perfectly pairing to the highly conserved primer binding site for methionyl initiator tRNA that is essential for reverse transcription. We investigated the possible origins of this miRNA, and present evidence that the pre‐miR1511 hairpin structure probably derived from a locus coding for tRNA iM et through a single microinversion event. Our study shows that this miRNA targets retrotransposons specifically and constitutively, and contributes to features such as genome stability, size and architecture in a far more direct way than previously thought. Significance Statement: Transcriptional gene silencing of transposons is usually attributed to small interfering RNAs (siRNAs). Here we show that a microRNA, miR1511, post‐transcriptionally silences LTR retrotransposons by targeting the evolutionary conserved primer binding site required for reverse transcription. We suggest that this silencing mechanism might be widespread as other miRNA families share core sequence identity with miR1511.