LfiRAV7 antagonizes LfiGI to regulate gibberellin biosynthesis and modulate plant height of crape myrtle.

The regulatory mechanism underlying plant height determination in woody plants remains a long-standing key scientific issue, and the coordinated manner by which positive and negative regulators maintain endogenous hormone homeostasis and modulate final plant architecture is still poorly understood. Here, we identified LfiRAV7 as a pivotal negative regulator of internode elongation in Lagerstroemia indica, providing novel insights into the functional role of APETALA2/Ethylene-Responsive Factor (AP2/ERF) family Related to ABI3/VP1 (RAV) members in governing woody plant architecture. Silencing of LfiRAV7 alleviated its transcriptional repression on plant height-related pathways, resulting in a 43.3% increase in gibberellin (GA) content and a 30.2% reduction in auxin (IAA) abundance, which further facilitated cell division and consequently promoted internode elongation. Protein-protein interaction assays confirmed that LfiRAV7 physically interacts with the positive regulator LfiGI (GIGANTEA). Silencing of LfiGI suppressed GA biosynthesis and inhibited both cell division and expansion. Integrated multi-omics analysis combining DAP-seq and RNA-seq demonstrated that LfiRAV7 did not exert widespread effects on metabolic pathways; instead, it directly bound to the E-box motif of LfiGA3ox, encoding the terminal rate-limiting enzyme of the GA biosynthesis pathway, and repressed its transcription. Collectively, we uncovered an antagonistic regulatory module consisting of LfiRAV7 and LfiGI, which not only revealed a previously uncharacterized genetic mechanism underlying the regulation of endogenous hormone homeostasis and morphogenesis in woody plants, but also offered key candidate targets for directed creation of ideal plant architecture in woody ornamental species.