Home
This Title All WIREs
WIREs RSS Feed
How to cite this WIREs title:
WIREs RNA
Impact Factor: 4.928

New insights into pri‐miRNA processing and accumulation in plants

Full article on Wiley Online Library:   HTML PDF

Can't access this content? Tell your librarian.

MicroRNAs (miRNAs) regulate many biological processes such as development, metabolism, and others. They are processed from their primary transcripts called primary miRNA transcripts (pri‐miRNAs) by the processor complex containing the RNAse III enzyme, DICER‐LIKE1 (DCL1), in plants. Consequently, miRNA biogenesis is controlled through altering pri‐miRNA accumulation and processing, which is crucial for plant development and adaptation to environmental changes. Plant pri‐miRNAs are transcribed by DNA‐dependent RNA polymerase II (Pol II) and their levels are determined through transcription and degradation, whereas pri‐miRNA processing is affected by its structure, splicing, alternative splicing, loading to the processor and the processor activity, which involve in many accessory proteins. Here, we summarize recent progresses related to pri‐miRNA transcription, stability, and processing in plants. WIREs RNA 2015, 6:533–545. doi: 10.1002/wrna.1292 This article is categorized under: Regulatory RNAs/RNAi/Riboswitches > Biogenesis of Effector Small RNAs
Simplified model for plant microRNAs (miRNA) pathway. After polymerase II (Pol II)‐dependent transcription, primary miRNA transcripts (pri‐miRNAs) are processed to the miRNA/miRNA* duplex through two steps cleavage by DICER‐LIKE1 (DCL1) in nucleus. The resulting miRNA/miRNA* duplex is then methylated by HUA1 ENHANCER1 (HEN1), which likely happens in nucleus. miRNAs are then loaded into ARGONAUTE1 (AGO1) to direct target cleavage or translational inhibition.
[ Normal View | Magnified View ]
Protein phosphorylation status affects the efficiency of primary miRNA transcript (pri‐miRNA) processing. (a) The phosphorylation status of HYPONASTIC LEAVES1 (HYL1) influences the DICER‐LIKE1 (DCL1) activity. Mitogen‐activated Protein Kinase (MPK3)‐mediated HYL1 phosphorylation decreases the cleavage efficiency and accuracy of pri‐miRNAs. C‐terminal domain phosphatase‐like 1 (CPL1)‐directed HYL1 dephosphorylation requires SERRATE (SE)‐dependent CPL1–HYL1 interaction and promotes DCL1 activity. (b) The phosphorylation status of DCL1 affects the DCL1–DDL interaction and pri‐miRNA processing
[ Normal View | Magnified View ]
Structures of primary miRNA transcripts (pri‐miRNAs) affect their processing patterns. (a) Base‐to‐loop processing of pri‐miRNAs. Some pri‐miRNAs with a ∼15 bp stem followed by an internal loop below the miRNA/miRNA* are cut first at a position distal to the loop and then a second cut at a position proximal to the loop that releases the miRNA/miRNA* duplex. (b) Sequential base‐to‐loop processing of pri‐miRNAs. Some pri‐miRNAs with long stems are initially cleaved at a position distal to the loop, which is ∼21 nt away from miRNA/miRNA*. miRNA/miRNA* then is released through sequential cleavage. There is often a 15 bp stem followed by an internal loop below the first cut position. (c) Loop‐to‐base processing pattern of pri‐miRNAs. pri‐miRNAs containing a structured and homogeneous terminal region with a ∼42 bp stem and a small loop usually are initially cleaved at a position proximal to the loop. (d) Sequential loop‐to‐base processing pattern of pri‐miRNAs. Some pri‐miRNAs with long stem loops are processed through multiple cleavages starting from the position proximal to the loop. (e) Bidirectional processing of pri‐miRNAs with a multibranched terminal loop. Some pri‐miRNAs with multibranched loops can be processed bidirectionally. However, not all processing patterns are productive.
[ Normal View | Magnified View ]
Diagram of the putative primary miRNA transcript (pri‐miRNA) processing complex. The known components associated with the Dicer‐LIKE1 (DCL1) complex include: CAP BINDING PROTEIN 20/80 (CBP20/80), SERRATE (SE), HYPONASTIC LEAVES1 (HYL1), TOUGH (TGH), NOT2, Cell Division Cycle 5 (CDC5), PLEIOTROPIC REGULATORY LOCUS 1 (PRL1), and DDL. Among of them, CDC5 and NOT2 do not interact with HYL1, suggesting that the components in the DCL1 complex may not be tightly associated. Alternatively, multiple subcomplexes containing DCL1 may exist. The 5′ cap structure of pri‐miRNAs, PRL1, and DDL prevents pri‐miRNAs from degradation.
[ Normal View | Magnified View ]
Transcriptional control of miRNA‐coding gene (MIR) expression in plants. (a) Diagram of polymerase II (Pol II)‐associated transcription factors with a general role in MIR transcription. (b) Temporal, spatial, and physiological regulation of MIR156 and MIR172 at transcriptional levels. (c) Spatial regulation of MIR165/166 at transcriptional levels during root development. After produced in from the vascular cylinder, SHORT ROOT (SHR), a transcription factor, moves into the endodermis to activate SCARECROW (SCR). These two transcription factors then initiate the expression MIR165A and MIR166B in the endodermis, repressing the expression of PHB, a transcription factor, in the endodermis and stele periphery. En, endodermis; PE, pericycle; PX, protoxylem.
[ Normal View | Magnified View ]
miRNA‐coding genes (MIRs) with various structures. (a) Diagram of typical intergeneric MIRs with or without introns. (b) Diagram of a polycistronic MIR from intergenic region. (c) Diagram of an intergenic MIR with a stem loop generating multiple small RNAs. (d) Diagram of typical intragenic MIRs residing in the exon or intron of host genes. (e) Diagram of typical MIRs rose from transposable elements.
[ Normal View | Magnified View ]

Browse by Topic

Regulatory RNAs/RNAi/Riboswitches > Biogenesis of Effector Small RNAs

Access to this WIREs title is by subscription only.

Recommend to Your
Librarian Now!

The latest WIREs articles in your inbox

Sign Up for Article Alerts