Integration of physiological and transcriptomic analysis reveals the anti-yellowing mechanism of high O2/CO2 pretreatment in fresh-cut broccoli (Brassica oleracea L. var. italica).

High O2/CO2 pretreatment (HOCP) is an effective measurement in delaying postharvest senescence in horticultural product. However, the precise mechanism of yellow inhibiting, especially in fresh-cut broccoli, remains ambiguous. This study explored the impact of HOCP on yellowing in fresh-cut broccoli using physiological and transcriptomic analyses. The results showed that, 50 % O2 + 50 % CO2 (50 HOCP) effectively delayed yellowing and extended shelf-life by significantly retarding the degradation of chlorophyll, ascorbate, and protein, enhancing overall antioxidant capacity, and reducing malondialdehyde accumulation. Further research indicated that HOCP delay yellowing by reducing reactive oxygen species (ROS), enhancing antioxidant capacity, maintaining more intact chloroplasts and the retention of high-level water content. Transcriptomic analysis revealed that HOCP treatment delayed of yellowing via down-regulating many key genes involved in multiple metabolic pathways: (1) Chlorophyll degradation pathway genes (e.g., BoNYC1, BoCLH, BoSGR, BoPAO, BoRCCH); (2) β-carotene and abscisic acid (ABA) biosynthesis genes (e.g., BoBCH, BoLUT5, BoCCD8, BoNCED, BoABA2, BoCYP707A), leading to reduced β-carotene and ABA levels; (3) Flavonoid biosynthesis genes (e.g., BoCHI, BoC4H, BoFLS, BoC3'H, BoCOMT), resulting in decreased flavonoid content. Our findings establish a novel multi-pathway regulatory mechanism for HOCP in suppressing postharvest yellowing, offering significant insights for developing strategies to improve the quality and shelf-life of fresh-cut broccoli. Therefore, as a safe, efficient, convenient, and low-cost technique, HOCP is recommended for the yellowing inhibition and pigments regulation of fresh-cut broccoli and other vegetables.