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

RCF1 is a highly conserved DEAD-box helicase found in yeast, plants and mammals. Studies about the functions of RCF1 in plants are limited. Here we uncovered the functions of RCF1 inArabidopsis thalianaas a player in pri-miRNA processing and splicing, as well as in pre-mRNA splicing. A mutant with miRNA biogenesis defects was isolated and the defect was traced to a recessive point mutation inRCF1(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 inrcf1-4. Together, this work uncovers roles for RCF1 in miRNA biogenesis and RNA splicing inArabidopsis.One-sentence summaryRCF1 promotes not only the processing of pri-miRNAs, but also the splicing of intron-containing pri-miRNAs, therefore promotes miRNA biogenesis.