The DEAD-box helicase RCF1 plays roles in miRNA biogenesis and RNA splicing in Arabidopsis

RCF1 is a highly conserved DEAD-box helicase found in yeast, plants and mammals. Little is known about the biological functions of RCF1 in plants. Here we uncovered the functions of RCF1 in Arabidopsis thaliana as a player in pri-miRNA processing and splicing, as well as in pre-mRNA splicing. A mutant with global defects in the biogenesis of miRNAs was isolated and the defect was traced to a recessive point mutation in RCF1 (rcf1-4). We show that RCF1 promotes D-body formation and facilitates the interaction between pri-miRNAs and HYL1. Finally, we show that intron-containing pri-miRNAs and pre-mRNAs exhibit a global splicing defect in rcf1-4. Together, this study reveals roles for Arabidopsis RCF1 in miRNA biogenesis and RNA splicing.