Biogenesis, Turnover, and Mode of Action of Plant MicroRNAs

Abstract

(K.R.).MicroRNAs (miRNAs) are small RNAs that control gene expression through silencing of target mRNAs. Mature miRNAs are processed from primary miRNA transcripts by the endonuclease activity of the DICER-LIKE1 (DCL1) protein complex. Mechanisms exist that allow the DCL1 complex to precisely excise the miRNA from its precursor. Our understanding of miRNA biogenesis, particularly its intersection with transcription and other aspects of RNA metabolism such as splicing, is still evolving. Mature miRNAs are incorporated into an ARGONAUTE (AGO) effector complex competent for target gene silencing but are also subjected to turnover through a degradation mechanism that is beginning to be understood. The mechanisms of miRNA target silencing in plants are no longer limited to AGO-catalyzed slicing, and the contribution of translational inhibition is increasingly appreciated. Here, we review the mechanisms underlying the biogenesis, turnover, and activities of plant miRNAs.

Genome-Wide Characterization of Maize Small RNA Loci and Their Regulation in the required to maintain repression6-1 (rmr6-1) Mutant and Long-Term Abiotic Stresses

“…In general, the wild-type and rmr6-1 mutant plants responded differently to the treatments in terms of most effective stress (drought for the wild-type and the combined stress for rmr6-1) and in terms of miRNA families altered, which were mostly different between the two genotypes. These differences were not expected, because miRNAs are transcribed by Pol II (Rogers and Chen, 2013) and in control conditions miRNAs were not altered in rmr6-1. It is possible that these differences might be secondary effects of the mutation.…”

“…The stems are precisely cleaved by the DICER-LIKE 1 protein, liberating a miRNA/miRNA* duplex (for review, see Rogers and Chen, 2013). After the duplex is loaded into ARGONAUTE 1, the miRNA guide strand is most frequently retained and directs target repression, while the miRNA* is more often rapidly degraded.…”

Gene silencing in microalgae: Mechanisms and biological roles

“…Based on structural studies, they are characterized by amino-terminal (N-terminal), PAZ (Piwi, Argonaute, Zwille), MID (middle) and PIWI domains, the latter being related to RNase H (Carthew and Sontheimer, 2009;Meister, 2013;Burroughs et al, 2014). Some AGO-Piwi polypeptides function as sRNA-guided endonucleases that cleave complementary transcripts, whereas others lack endonucleolytic activity and may be part of complexes involved in nondegradative RNAi mechanisms such as translation repression (Cerutti and Casas-Mollano, 2006;Carthew and Sontheimer, 2009;Meister, 2013;Rogers and Chen, 2013). In certain species, RDRs also play an important role in RNAi, either by producing an initiating dsRNA trigger from singlestranded transcripts or by enhancing the RNAi response through amplification of the sRNA amount (Cerutti and Casas-Mollano, 2006;Burroughs et al, 2014).…”

“…In the best-characterized RNAi pathway, a variety of double-stranded RNA (dsRNA) precursors are processed into small RNAs (sRNAs) by the RNaseIII-like endonuclease Dicer (Cerutti and Casas-Mollano, 2006;Carthew and Sontheimer, 2009;Rogers and Chen, 2013). These sRNAs are then incorporated into effector complexes, which include members of the AGO-Piwi family of proteins named after A. thaliana ARGONAUTE1 and Drosophila melanogaster Piwi (Cerutti and Casas-Mollano, 2006;Meister, 2013;Burroughs et al, 2014).…”

Identification of microRNA elements from genomic data of European hazelnut (Corylus avellana L.) and its close relatives

“…These small but effective regulators are important elements in elucidating gene regulation pathways in the cell (Tang, 2010;Rogers and Chen, 2013). To date, many studies have focused on the identification of miRNAs methods including cloning, genetic screening, microarray profiling and computational mining approaches (Zhang, 2006).…”