Redundant and specific roles of individual MIR172 genes in plant development.

Lin Han,Xuemei Chen,Tian-Qi Zhang,Ning Ma,Jia-Wei Wang,Heng Lian,Chuan-Miao Zhou,Long Wang

doi:10.1371/journal.pbio.3001044

Abstract

Evolutionarily conserved microRNAs (miRNAs) usually have high copy numbers in the genome. The redundant and specific roles of each member of a multimember miRNA gene family are poorly understood. Previous studies have shown that the miR156-SPL-miR172 axis constitutes a signaling cascade in regulating plant developmental transitions. Here, we report the feasibility and utility of CRISPR-Cas9 technology to investigate the functions of all 5 MIR172 family members in Arabidopsis. We show that an Arabidopsis plant devoid of miR172 is viable, although it displays pleiotropic morphological defects. MIR172 family members exhibit distinct expression pattern and exert functional specificity in regulating meristem size, trichome initiation, stem elongation, shoot branching, and floral competence. In particular, we find that the miR156-SPL-miR172 cascade is bifurcated into specific flowering responses by matching pairs of coexpressed SPL and MIR172 genes in different tissues. Our results thus highlight the spatiotemporal changes in gene expression that underlie evolutionary novelties of a miRNA gene family in nature. The expansion of MIR172 genes in the Arabidopsis genome provides molecular substrates for the integration of diverse floral inductive cues, which ensures that plants flower at the optimal time to maximize seed yields.

Highlights

MicroRNAs, a class of small single-stranded noncoding RNAs that range in length from 20 to 22 nucleotides, play important roles in regulating gene expression [1,2,3,4,5]
For the MIR172A and MIR172C loci, the entire stem-loop regions were deleted; for the MIR172B and MIR172D loci, the deletions occurred in the loops of the stem-loop regions; for the MIR172E locus, the sequence corresponding to the miRNA was deleted
We found that the flowering of both WT and mir172 quintuple mutant plants was accelerated at 28 ̊C (Fig 7A), indicating that elevated ambient temperature promotes flowering independent of miR172

Summary

Introduction

MicroRNAs (miRNAs), a class of small single-stranded noncoding RNAs that range in length from 20 to 22 nucleotides (nt), play important roles in regulating gene expression [1,2,3,4,5]. The ancient (i.e., evolutionarily conserved) miRNAs such as miR156, miR159/ 319, miR160, miR165/6, miR171, and miR172 are present in high copy numbers in the genome of Arabidopsis thaliana [10]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Methods

Results

Conclusion