Arabidopsis RBV is a conserved WD40 repeat protein that promotes microRNA biogenesis and ARGONAUTE1 loading

Chao Liang,Bailong Zhang,Ting Lan,Fei Wang,Qiang Cai,Shaofang Li,Beixin Mo,Lei Gao,Chi Xu,Xuemei Chen,Chenjiang You,Dechang Cao

doi:10.1038/s41467-022-28872-x

Abstract

MicroRNAs (miRNAs) play crucial roles in gene expression regulation through RNA cleavage or translation repression. Here, we report the identification of an evolutionarily conserved WD40 domain protein as a player in miRNA biogenesis in Arabidopsis thaliana. A mutation in the REDUCTION IN BLEACHED VEIN AREA (RBV) gene encoding a WD40 domain protein led to the suppression of leaf bleaching caused by an artificial miRNA; the mutation also led to a global reduction in the accumulation of endogenous miRNAs. The nuclear protein RBV promotes the transcription of MIR genes into pri-miRNAs by enhancing the occupancy of RNA polymerase II (Pol II) at MIR gene promoters. RBV also promotes the loading of miRNAs into AGO1. In addition, RNA-seq revealed a global splicing defect in the mutant. Thus, this evolutionarily conserved, nuclear WD40 domain protein acts in miRNA biogenesis and RNA splicing.

Highlights

MicroRNAs play crucial roles in gene expression regulation through RNA cleavage or translation repression
We performed an ethylmethane sulfonate mutagenesis screen for Arabidopsis mutants in miRNA biogenesis, utilizing the veincentered leaf beaching phenotype caused by the phloem-specific expression of an artificial miRNA targeting the SULFUR (SUL) gene as a visible marker for miRNA activity[29]
To rule out the possibility that REDUCTION IN BLEACHED VEIN AREA (RBV) indirectly regulated miRNA accumulation by affecting the expression of the miRNA biogenesis machinery, we examined the expression of the known genes involved in miRNA biogenesis, and no significant changes were observed in rbv-1 (Supplementary Fig. 6b, c)

Summary

Introduction

MicroRNAs (miRNAs) play crucial roles in gene expression regulation through RNA cleavage or translation repression. RNA-seq revealed a global splicing defect in the mutant This evolutionarily conserved, nuclear WD40 domain protein acts in miRNA biogenesis and RNA splicing. Target gene expression is regulated by miRNAs post-transcriptionally through RNA cleavage or translation repression[2]. In Arabidopsis, NOT2, CDC5, and Elongator interact with both Pol II and DCL16–8, suggesting that primiRNA transcription and processing may be coordinated in plants. The efficient processing of pri-miRNAs requires the doublestranded RNA-binding protein HYPONASTIC LEAVES1 (HYL1)[16,17] and the zinc finger protein SERRATE (SE)[18,19], which form the microprocessor complex with DCL120,21. On the basis of these results, we propose that RBV may act to coordinate MIR transcription and pri-miRNA processing in plant miRNA biogenesis. RBV has a global role in pre-mRNA splicing, affecting a set of short introns

Methods

Results

Conclusion