Arabidopsis RBV is a conserved WD40 repeat protein that promotes microRNA biogenesis and ARGONAUTE1 loading [sRNA-seq]
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. Overall design: small RNA profiles of 15-d-old Arabidopsis thaliana seedlings with amiR-SUL, amiR-SUL ab57, wild type (Columbia background)and ab57 in Col background input and after AGO1 IP  were generated by deep sequencing, in triplicate, using Illumina HiSeq2500 and illumina Nextseq, respectively.