Two miRNAs are sufficient for C. elegans embryogenesis
The Microprocessor, composed of Drosha and Pasha/DGCR8, is necessary for the biogenesis of canonical microRNAs (miRNAs), and required for animal embryogenesis. However, the cause for this requirement is largely unknown. The Microprocessor may be required to produce one or few essential miRNAs, or alternatively, many individually non-essential miRNAs. Additionally, Drosha and Pasha/DGCR8 may be required for processing non-miRNA substrates. To distinguish between these possibilities, we developed a system in C. elegans to stringently deplete embryos from the Microprocessor and miRNAs. We show that the early embryonic arrest upon loss of the Microprocessor is rescued by the addition of two individual miRNAs from the miR-35 and miR-51 families, resulting in morphologically normal larvae. Thus, just two canonical miRNAs are sufficient for morphogenesis and organogenesis in C. elegans, and indicate that miRNA processing explains the essential requirement for the Microprocessor during embryogenesis. Overall design: 22 small RNA libraries from C. elegans embryos / L1 larvae, as well as Arabidopsis total RNA for control purposes. Spike in oligos have been added [design based on (Lutzmayer et al., 2017, Sci Rep)] and used for absolute quantification of mature miRNA levels