Brassinosteroid and Light Quality Synergistically Regulate Aroma Biosynthesis via the CmBES1–4–CmDof13 Module in Postharvest Oriental Melon ( Cucumis melo )

Abstract Brassinosteroids and light quality regulate secondary metabolism in fruits, yet the synergistic control of volatile aroma biosynthesis in oriental melon (Cucumis melo var. makuwa) remains unclear. In this study, we used volatile metabolomics, RNA sequencing (RNA-seq), and DNA Affinity Purification Sequencing (DAP-seq) methods to show that red light combined with brassinosteroids effectively increased total volatiles, particularly esters, at day 6 after harvest. Weighted gene coexpression network analysis (WGCNA) identified a module strongly associated with ester content, in which the brassinosteroid-responsive transcription factor CmBES1–4 co-occurred with CmDof13 and the downstream target genes CmLOX18 and CmAAT1. DAP-seq analysis revealed that CmBES1–4 bound E-box and BRRE motifs genome-wide, thereby directly targeting CmDof13. Dual-luciferase, yeast one-hybrid, and EMSA assays confirmed that CmBES1–4 activated CmDof13 expression via E-box binding. These findings identified a novel light/BR–CmBES1–4–CmDof13–ester biosynthesis regulatory module, which provided theoretical insights for improving postharvest aroma quality in oriental melon.