Involved in the RNA silencing pathway. Cleaves double-stranded RNA to produce microRNAs (miRNAs) of 21-24 nucleotides which target the selective destruction of complementary RNAs. Regulates by this way the development of the plant. May not be involved in small interfering RNAs (siRNAs) production. May interact with ARGONAUTE1 or PINHEAD through their common PAZ domains. Severe dwarfism and dark green color. Seedling viability compromised. Belongs to the helicase family. Dicer subfamily.