Molecular regulation of oil gland development and biosynthesis of essential oils in <i>Citrus</i> spp.

Secretory structures in terrestrial plants serve as reservoirs for a variety of secondary metabolites. Among these, the secretory cavity of the Rutaceae family is notable for containing essential oils with a wide range of applications. However, the molecular basis underlying secretory cavity development is unknown. Here, we reveal a molecular framework for <i>Citrus</i> oil gland formation. Using genetic mapping and genome editing, we demonstrated that this process requires LATE MERISTEM IDENTITY1 (LMI1), a key regulator of leaf serration. A conserved GCC box element of the <i>LMI1</i> promoter recruits DORNROSCHEN-like (DRNL) for transcriptional activation. This <i>DRNL-LMI1</i> cascade triggers <i>MYC5</i> activation, facilitating the development of oil glands and the biosynthesis of essential oils. Our findings spotlight <i>cis</i>-regulatory divergence within leaf shape genes, propelling novel functional tissue formation.