LsRGL1 controls the bolting and flowering times of lettuce by modulating the gibberellin pathway

Bolting, which is a serious problem during lettuce (Lactuca sativa L.) production, is responsible for substantial annual yield and quality losses. Gibberellin plays a critical role in the regulation of lettuce bolting. Additionally, DELLA proteins negatively regulate the gibberellin signaling pathway. However, it is unclear if DELLA proteins are involved in the regulation of lettuce bolting. Therefore, in this study, we identified four DELLA-encoding genes in lettuce, including LsRGL1, which was highly expressed in the stem and negatively correlated with bolting. Knocking down this gene in lettuce promoted bolting, whereas its overexpression inhibited bolting and the biosynthesis of gibberellin and auxin. A transcriptome analysis revealed that genes involved in gibberellin and auxin biosynthesis and flowering were affected in the LsRGL1-overexpressing lines. The yeast two-hybrid and yeast one-hybrid assay results indicated that LsRGL1 can interact with LsGA3ox and the LsYUC4 promoter region. Considered together, the results of this study suggest LsRGL1 negatively regulates lettuce bolting. Furthermore, its function may depend on modifications to gibberellin and auxin levels mediated at the transcript and protein levels.