Hierarchical Regulatory Module AcERF1–AcHAT5–AcERF10 Modulates Ethylene‐Dependent Starch Degradation in Postharvest Kiwifruit

The transcriptional regulatory network underlying ethylene‐governed starch‐to‐sugar conversion remains poorly understood. We elucidated the hierarchical regulatory cascade linking ethylene signalling to starch degradation in postharvest kiwifruit. Ethylene treatment accelerated fruit softening, starch degradation, and soluble sugar accumulation, whereas 1‐methylcyclopropene treatment produced opposite effects in kiwifruit. Weighted gene co‐expression network analysis identified 3 β‐amylase genes ( AcBAM3.1/3.3/3.5 ) and 16 transcription factors (TFs) as highly correlated with starch‐to‐sugar conversion. AcERF10 was isolated as a direct transcriptional activator of AcBAM3.1/3.3/3.5 and the ethylene biosynthetic gene AcACO1 . AcERF10 overexpression promoted starch degradation and sugar accumulation; silencing this gene resulted in opposite phenotypes. AcERF10 was directly activated by AcERF1 and AcHAT5—TFs that are induced by ethylene. AcERF1 bound to and activated the promoter of AcHAT5 , while AcHAT5 bound to the AcERF10 promoter and interacted with AcERF10 to synergistically activate expression of AcBAMs and AcACO1 , identifying a regulatory cascade of AcERF1‐AcHAT5‐AcERF10. Overexpression of either AcERF1 or AcHAT5 promoted downstream gene expression, accelerated starch degradation, and enhanced sugar accumulation, whereas silencing of either gene suppressed these processes. This study uncovers an ethylene‐triggered, multi‐layer transcriptional regulatory network that governs starch‐to‐sugar conversion during postharvest kiwifruit ripening, providing new mechanistic insights into ethylene‐regulated fruit quality development during postharvest storage.