Distinct Transcriptomic Profile Underlying High CO₂ and Ethylene-Induced Deastringency in 'Daebong' Persimmon Fruit

Astringent persimmons (Diospyros kaki Thunb.) require effective postharvest deastringency treatments due to their high soluble tannin content at harvest. While high CO₂ and ethylene are commonly used to remove astringency, their different effects on fruit firmness and quality require cultivar-specific approaches. This study investigated the transcriptomic and biochemical responses of 'Daebong' persimmon to high CO₂ and ethylene treatments during deastringency. Both treatments significantly decreased soluble tannin and total phenolic content, enhancing fruit edibility. However, the firmness was maintained under high levels of CO₂, but it decreased quickly after exposure to ethylene. RNA-Seq analysis identified 2271 differentially expressed genes (DEGs) and revealed distinct transcriptional signatures for each treatment. CO₂ treatment activated hypoxia-responsive genes, stress-related transcription factors (e.g., WRKY, ERF14/26), and components of antioxidant defense (e.g., GSTU17, peroxidases), which contributed to oxidative stress reduction and preservation of firmness. On the other hand, ethylene treatment increased ethylene biosynthesis (ACS), signaling (EIN3-binding F-box), and ripening-related genes (polygalacturonase, laccase, ERF061/113), which promote cell wall degradation and softening. Functional enrichment analysis revealed that various regulatory mechanisms are responsible for the insolubilization of tannins, loss of antioxidants, and changes in firmness. These findings provide new insights into the molecular responses of pollination-constant astringent (PCA) persimmons, particularly the 'Daebong' cultivar, to postharvest deastringency treatments for the development of more effective postharvest management strategies. The results suggest that high CO₂ helps maintain fruit quality by promoting stress adaptation and suppressing pathways that lead to softening, whereas ethylene accelerates the ripening process by activating signaling pathways associated with ethylene.