CAD1 enhances antioxidant activity to facilitate cold storage by regulating flavonoid synthesis in cucumber

Abstract

Improving antioxidant activity to preserve nutritional quality and enhance environmental resilience is a primary goal in vegetable breeding. Cucumber is known to have relatively low antioxidant activity among commonly consumed vegetables, yet the specific genetic factors underlying this trait remain largely unexplored. In this study, a significantly divergence in the antioxidant activity of cucumber inbred lines was revealed by Ferric Ion Reducing Antioxidant Power (FRAP) assay. A gene responsible for this divergence, designated as Cvergence 1 (CAD1), was map-based cloned through Bulked Segregant Analysis (BSA) sequencing and molecular marker-assisted selection from a F₂ population. Subsequently, gene editing and overexpression analysis demonstrated that CAD1 is essential for antioxidant activity. Furthermore, qRT-PCR and phylogenetic tree analysis showed that CAD1 encodes a fruit-specific expressed MYB transcription factor. Comprehensive untargeted metabolomics analysis and Electrophoretic Mobility Shift Assay (EMSA) revealed that CAD1 transcriptionally activates genes involved in flavonoid synthesis, thereby promoting flavonoid production and boosting the antioxidant activity of cucumber. Finally, cold treatment showed that CAD1 improves cold storage resilience, which is directly activated by CsCBF2. In summary, this study provides valuable insights and data for breeding cucumbers with enhanced antioxidant activity.