NaHCO3 promotes postharvest de-astringency of Torreya grandis nuts via TgERF71-mediated activation of TgPDC1

Astringency caused by soluble tannins limits the eating quality of Torreya grandis nuts and necessitates postharvest de-astringency treatments. Sodium bicarbonate (NaHCO 3 ) can accelerate de-astringency, but its molecular basis remains unclear. Here, T. grandis nuts were immersed in 0.1 mol L -1 NaHCO 3 for 24 h and sampled during treatment and storage. NaHCO 3 accelerated post-ripening, promoted acetaldehyde accumulation, and enhanced the conversion of soluble tannins into insoluble tannins. By day 20, soluble tannin reduction in NaHCO 3 -treated nuts was 3.0-fold greater than in CK, accompanied by a 2.2-fold increase in insoluble tannins. Alcohol dehydrogenase and pyruvate decarboxylase activities increased, and TgADH5 and TgPDC1 were identified as the most responsive genes. Transient overexpression and virus-induced gene silencing confirmed that both genes promote tannin insolubilization. Transcriptome-guided screening identified TgERF71 , an ERF-VII transcription factor, as an upstream regulator that activated the TgPDC1 promoter by 3.6-fold in dual-luciferase assays and directly bound the promoter via yeast one-hybrid and electrophoretic mobility shift assays. Gain- and loss-of-function assays indicated that TgERF71 positively regulates TgPDC1 expression and insoluble tannin accumulation. These results suggest that TgERF71-mediated activation of TgPDC1 represents an important regulatory mechanism underlying NaHCO 3 -promoted postharvest de-astringency in T. grandis nuts, providing mechanistic support for a postharvest enhancement strategy.