Form follows function - structural interplay between DCL1 and pri-miRNAs.

MicroRNAs (miRNAs) guide post-transcriptional gene silencing in plants and shape developmental outcomes and environmental responses by precisely tuning gene expression. miRNAs originate from primary transcripts (pri-miRNAs) whose structural features - including internal loops, mismatches, and sequence motifs - facilitate interactions with the miRNA processing complex composed of DICER-LIKE 1 (DCL1), HYPONASTIC LEAVES 1 (HYL1), and SERRATE (SE). In vitro structural analyses of DCL1, HYL1, and SE proteins have elucidated their interactions with each other and with pri-miRNAs at unprecedented resolution. These findings highlight plant-specific processing features that are distinct from those of animals and suggest new avenues for manipulating miRNA pathways. We review recent progress in understanding the structural determinants of pri-miRNA processing, knowledge that may also be valuable for future applications in crop species through targeted genome editing.