Cleavage of INDOLE-3-ACETIC ACID INDUCIBLE28 mRNA by MicroRNA847 Upregulates Auxin Signaling to Modulate Cell Proliferation and Lateral Organ Growth in Arabidopsis

Abstract

MicroRNAs function in a range of developmental processes. Here, we demonstrate that miR847 targets the mRNA of the auxin/indole acetic acid (Aux/IAA) repressor-encoding gene IAA28 for cleavage. The rapidly increased accumulation of miR847 in Arabidopsis thaliana coincided with reduced IAA28 mRNA levels upon auxin treatment. This induction of miR847 by auxin was abolished in auxin receptor tir1-1 and auxin-resistant axr1-3 mutants. Further analysis demonstrates that miR847 functions as a positive regulator of auxin-mediated lateral organ development by cleaving IAA28 mRNA. Importantly, the ectopic expression of miR847 increases the expression of cell cycle genes as well as the neoplastic activity of leaf cells, prolonging later-stage rosette leaf growth and producing leaves with serrated margins. Moreover, both miR847 and IAA28 mRNAs are specifically expressed in marginal meristems of rosette leaves and lateral root initiation sites. Our data indicate that auxin-dependent induction of miR847 positively regulates meristematic competence by clearing IAA28 mRNA to upregulate auxin signaling, thereby determining the duration of cell proliferation and lateral organ growth in Arabidopsis. IAA28 mRNA encodes an Aux/IAA repressor protein, which is degraded through the proteasome in response to auxin. Altered signal sensitization to IAA28 mRNA levels, together with targeted IAA28 degradation, ensures a robust signal derepression.

The Accumulation of miRNAs Differentially Modulated by Drought Stress Is Affected by Grafting in Grapevine

“…A similar situation was observed previously for novel miRNAs isolated in this and other plant species (Mica et al, 2010;Li et al, 2011;Ren et al, 2012;Ge et al, 2013). Moreover, since miRNAs belonging to lowabundance categories have emerging big roles in plant developmental processes (Wang and Guo, 2015), we hypothesize that the analyzed novel miRNAs that are less abundant than conserved miRNAs could function to modulate the cross talk between plant development and the abiotic stress response. For instance, the novel candidate miRNA n_22 was predicted to target an MLO calmodulin-binding protein (MLO16)-encoding transcript belonging to a plant gene family involved in pathogen defense and abiotic stress response processes (Piffanelli et al, 2002).…”

Genome-wide profiling of sRNAs in the Verticillium dahliae-infected Arabidopsis roots

“…A large number of candidate genes that are potentially regulated by auxins, including the ARF and IAA gene family in Arabidopsis , are targets of miRNAs (Szemenyei et al 2008; Chandler 2016). Previously, we demonstrated that auxin-dependent induction of miR847 is involved in regulating meristematic competence by targeting the mRNA of IAA28 to up-regulate auxin signalling (Wang and Guo 2015). Furthermore, many ARF genes are directly regulated by at least one miRNA in response to biotic or abiotic stress, such as ARF6 and ARF8 are targeted by miR167 while ARF10, ARF16 and ARF17 are targeted by miR160 (Chandler 2016; Li et al 2016).…”

Dynamic roles of microRNAs in nutrient acquisition and plant adaptation under nutrient stress: A review

“…Another detailed study reported by Gutierrez et al (2012), demonstrated the coordinated roles of miR160 and miR167 targeting auxin responsive genes indispensable for root architecture remodeling. Similarly, overexpression of miR847 exhibited more lateral roots thereby modulating indole acetic acid (IAA) related genes (Wang and Guo, 2015). Plants respond according to the availability status of macroand micro-nutrients and in turn adapt certain strategies at the molecular level in order to efficiently use available resources.…”