Over-expression of microRNA171 affects phase transitions and floral meristem determinancy in barley

Abstract

BackgroundThe transitions from juvenile to adult and adult to reproductive phases of growth are important stages in the life cycle of plants. The regulators of these transitions include miRNAs, in particular miR156 and miR172 which are part of a regulatory module conserved across the angiosperms. In Arabidopsis miR171 represses differentiation of axillary meristems by repressing expression of SCARECROW-LIKE(SCL) transcription factors, however the role of miR171 has not been examined in other plants.ResultsTo investigate the roles of mir171 and its target genes in a monocot, the Hvu pri-miR171a was over-expressed in barley (Hordeum vulgare L. cv. Golden promise) leading to reduced expression of at least one HvSCL gene. The resulting transgenic plants displayed a pleiotropic phenotype which included branching defects, an increased number of short vegetative phytomers and late flowering. These phenotypes appear to be the consequence of changes in the organisation of the shoot meristem. In addition, the data show that miR171 over-expression alters the vegetative to reproductive phase transition by activating the miR156 pathway and repressing the expression of the TRD (THIRD OUTER GLUME) and HvPLA1 (Plastochron1) genes.ConclusionsOur data suggest that some of the roles of miR171 and its target genes that have been determined in Arabidopsis are conserved in barley and that they have additional functions in barley including activation of the miR156 pathway.

Interaction between Two Timing MicroRNAs Controls Trichome Distribution in Arabidopsis

“…Notably miR171a* is also functional in gene silencing and the miR171a*- SU(VAR)3-9 HOMOLOG8 pair was proposed to have evolved very recently in the Arabidopsis lineage [44]. A recent report showed that overexpression of miR171 ( Hvu-pri-miR171a ) in barley up-regulated miR156 and repressed vegetative phase transitions [49], which is in contrast with the opposite effects of the two miRNAs in Arabidopsis described herein and reported by others [26], [29], [50]. Whether the interplay between the two conserved aging miRNAs varies with plant taxa is a subject of further study.…”

The rolB gene activates the expression of genes encoding microRNA processing machinery

“…Arabidopsis plants overexpressing miR168a display abscisic acid hypersensitivity and drought tolerance (Li et al 2012). The overexpression of miR172 promotes leaf length elongation in adult plants and increases root and hypocotyl growth (Kim et al 2014), and miR171 overexpression affects floral meristem determinancy in barley (Curaba et al 2013).…”

Short tandem target mimic rice lines uncover functions of miRNAs in regulating important agronomic traits

“…Barley plants overexpressing miR171 were dwarf and had a reduced number of tillers compared with WT, whereas rice miR171 overexpression lines were taller and had increased tiller numbers compared with WT (45,46). In Arabidopsis, miR171 targets the scarecrow-like (SCL) transcription factors and is thought to regulate meristematic cell proliferation, polar organization, and chlorophyll synthesis (47,48).…”