Keep calm and carry on: miRNA biogenesis under stress

Abstract

Summary MicroRNAs (miRNAs) are major post‐transcriptional regulators of gene expression. Their biogenesis relies on the cleavage of longer precursors by a nuclear localized processing machinery. The evolutionary preference of plant miRNAs to silence transcription factors turned these small molecules into key actors during growth and adaptive responses. Furthermore, during their life cycle plants are subject to changes in the environmental conditions surrounding them. In order to face these changes, plants display unique adaptive capacities based on an enormous developmental plasticity, where miRNAs play central roles. Many individual miRNAs have been shown to modulate the plant response to different environmental cues and stresses. In the last few years, increasing evidence has shown that not only individual genes encoding miRNAs but also the miRNA pathway as a whole is subject to regulation in response to external stimulus. In this review, we discuss the current knowledge about the miRNA pathway. We dissect the pathway to analyze the events leading to the generation of these small RNAs and emphasize the regulation of core components of the miRNA biogenesis machinery.

Small RNA Mobility: Spread of RNA Silencing Effectors and its Effect on Developmental Processes and Stress Adaptation in Plants

“…In fact, it has recently begun to emerge that a variety of environmental alterations can differently affect miRNA production and stability by directly altering the main enzymes related to their entire biogenesis pathways. In response to specific stress signals, the whole machinery associated with miRNA production can be turned down through the establishment of feedback regulatory mechanisms [44]. An excellent example is represented by 22-nt miR168 molecules that are produced instead of the 21-nt long isoforms of the same miRNA and that are preferentially complexed with AGO10 to trigger the synthesis of secondary siRNAs from AGO1 loci [134].…”

“…The transport of these molecules within the plant and their consequent effects, including the transgenerational inheritance of epigenetic marks underlying stress memory phenomena, require further investigations to be deciphered completely [43]. Finally, another noteworthy aspect pertains to the flexible regulation of small RNA biogenesis in response to specific stress signals [44].…”

The miR156: A Master Regulator to Harmonize Complex Biofuel Traits in Lignocellulosic Biomass Crops

“…It also reported that miRNAs [98,99] further lead to the synthesis of secondary siRNAs called phasiRNAs and/or easiRNAs. In recent studies, it observed that the multistep process of miRNA biogenesis and degradation plays a crucial role in the "fine-tuning" of plant response to growth and development under environmental stresses [100,101]. Furthermore, it is also noticed that individual components of the miR156 biogenesis pathway such as D-body proteins like DCL1, AGO (Argonaut), HYL 1, SE, DRB2 (Double-stranded RNA binding proteins-2) and miRNA-miRNA* duplex, and their interactome also plays a crucial role to produce a final response at the plant level to external as well as internal perturbations, [102].…”

Argonaute Proteins: Why Are They So Important for the Legume–Rhizobia Symbiosis?

“…Recent evidence indicates that AGO proteins respond to environmental stimuli (Manavella et al, 2019). The direct involvement of plant AGO proteins in biotic interactions is also well known, mainly for plant defense against bacteria and virus (Raja et al, 2008; Carbonell and Carrigton, 2015; Fátyol et al, 2016).…”