Involved in the microRNA (miRNA) and short interfering RNA (siRNA) biogenesis. May facilitate DCL1 to access or recognize primary miRNAs. Binds RNA non-specifically. Interacts with DCL1 (via N-terminus). Expressed in roots, lateral roots, vascular strands of roots and leaves, vegetative meristems, pollen and developing seeds. Delayed growth and reduced fertility. Defective roots, shoots and flowers. Reduced seed set. Reduced levels of primary miRNAs as well as mature miRNAs.