The SlHYL1 ‐ SlRBP1 module integrates gibberellin metabolism to promote plant height in tomato ( Solanum lycopersicum )

SUMMARY Plant height is an essential agronomic trait that significantly influences crop yield and quality. The HYPONASTIC LEAVES 1 (HYL1), a core component of microRNA biogenesis, remains poorly understood in terms of its regulatory mechanisms on agronomic traits in tomato ( Solanum lycopersicum , Sl). In this study, we demonstrated that CRISPR/Cas9‐mediated knockout of SlHYL1 caused dwarfism, and partial suppression of SlHYL1 in tomato cultivar “Ailsa Craig” (AC) via RNA interference (RNAi) increased internode number but reduced internode length, resulting in a semi‐dwarf phenotype, confirming the role of SlHYL1 in regulating plant height. Cytological analysis showed that SlHYL1 suppression decreased both cell number and size within internodes. Yeast two‐hybrid screening identified that SlHYL1 interacted with another tomato RNA‐binding protein 1 (SlRBP1). Knockdown of SlRBP1 resembled the SlHYL1‐RNAi semi‐dwarf phenotype. Further studies revealed that the SlHYL1‐SlRBP1 module additively promotes the expression of gibberellin (GA) biosynthetic genes, thereby facilitating GA accumulation. Additionally, the dwarf phenotypes of both SlHYL1‐RNAi and SlRBP1‐RNAi plants were partially rescued by exogenous GA 3 application. Notably, unlike SlHYL1, SlRBP1 did not affect the biogenesis of most miRNAs. In summary, our findings demonstrate that the SlHYL1‐SlRBP1 module regulates tomato plant height by enhancing GA accumulation.