Eggplant transcription factor SmERF118 mediates light signaling regulation of anthocyanin synthesis

Light significantly impacts anthocyanin synthesis. The anthocyanin content serves as a vital quality indicator for purple eggplant (Solanum melongena L.). Cultivation under low-light conditions often results in inadequate coloration of the purple eggplant rind, adversely affecting fruit quality. This study, aimed to introduce SmERF118, a light-induced ethylene response factor (ERF) transcription factor, as a positive regulator of anthocyanin synthesis in eggplant pericarp under low-light conditions, yet its precise mechanism remained unclear. Further, SmHY5, a bZIP transcription factor was identified, which bound to the G-box element of the SmERF118 promoter, thereby activating its expression. The overexpression of SmERF118 significantly enhanced anthocyanin accumulation in the eggplant stalks. Transcriptome analysis corroborated that the differentially expressed genes in SmERF118-overexpressing plants are predominantly enriched in pathways associated with flavonoid biosynthesis. The analysis revealed a significant upregulation of key transcription factors and structural genes pivotal to anthocyanin biosynthesis. Through a yeast two-hybrid screening assay, SmMYB1, a pivotal MYB transcription factor that promotes anthocyanin synthesis, were screened as an interacting protein of SmERF118. Subsequent bimolecular fluorescence complementation, GST pull-down and co-immunoprecipitation assays confirmed the interaction between SmERF118 and SmMYB1 both in vivo and in vitro. Additionally, dual-Luciferase (dual-LUC) and transient overexpression experiments demonstrated that SmERF118 and SmMYB1 formed a complex that jointly activated essential genes involved in anthocyanin synthesis, specifically SmCHS and SmDFR, thereby enhancing anthocyanin accumulation. Ultimately, the study elucidated that light signaling promoted anthocyanin synthesis in eggplant via SmERF118-SmMYB1 regulatory module. These findings contributed to a refined understanding of the molecular regulatory network governing anthocyanin synthesis in eggplant and enhanced the comprehension of how light signaling regulated this process.