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.

Immune proteases are promising targets for protein engineering to boost disease resistance in plants.