MicroRNAs (miRNAs) and Plant Development

microRNAs (miRNAs) are a novel class of 21–24 nucleotide, endogenous, noncoding small ribonucleic acids (RNAs) that play critical roles in diverse biological processes such as: development, cellular differentiation, cell-cycle control, apoptosis and oncogenesis. In plants, roles of miRNAs in development have been extensively investigated in recent years. This review highlights and discusses the current knowledge about the roles of microRNAs in leaf development, patterning and polarity, floral identity and flower development, developmental phase transition and flowering time, shoot and root development, vascular development and hormone signalling for plant development.

Keywords: microRNAs; plant development; gene regulation; transcription factors; arabidopsis

Figure 1. miRNAs regulate various aspects of plant development. miRNAs regulate plant development via their posttranscriptional control on the expression of many transcription factors and F-box proteins. This control that fine-tunes the regulatory network of plant development is an important level of regulation, which ensures a proper development of a plant.
Figure 2. Biogenesis of miRNA and ta-siRNA in the RNA-silencing pathways.

(a) miRNA genes is transcribed by Pol II to produce fold-back structure of pri-miRNA transcripts. Following transcription, the pri-miRNA is processed by DCL1 with the aid of HYL1 and probably other unknown factors. In contrast to animal miRNA biogenesis, in which miRNA precursor (pre-miRNA) is generated by a different set of enzymes, the detail for the production of plant pre-miRNAs by DCL1 complex is unclear. In plants, miRNA duplex are first methylated by HEN1 in nucleus and then exported to the cytoplasm by HASTY. Mature methylated miRNAs are assembled into AGO1-containing complex or RISC that target complementary mRNAs for cleavage or translation repression. (b) pri-tasiRNA transcripts are transcribed in the same way as primary miRNAs (pri-miRNAs). miRNA-directed AGO1-associated RISC guides double cleavage on the pri-tasiRNA to generate templates of RNA fragments for RDR6, an RNA dependent RNA polymerase, to produce long double stranded RNAs (dsRNAs). DCL4 initiates processing of the dsRNA to produce phased ta-siRNAs that are also methylated by HEN1. ta-siRNAs are subsequently assembled into RISC to cleave homologous mRNAs.
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Wang, Wang‐Xia, Gaffney, Bobby, Hunt, Arthur G., and Tang, Guiliang(Jul 2007) MicroRNAs (miRNAs) and Plant Development. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0020106]