Oregano Oil Fumigation Suppresses Postharvest Yellowing in Broccoli by Enhancing Antioxidant Capacity

Abstract The present study utilized integrated physiological, transcriptomic, and metabolomic analyses to comprehensively investigate the molecular mechanisms through which oregano oil (OO) fumigation delays postharvest yellowing of broccoli during storage. Results indicated that the OO treatment significantly suppressed respiration and ethylene biosynthesis, reduced reactive oxygen species (ROS) accumulation, and membrane lipid peroxidation, while activating the antioxidant enzyme system in broccoli. OO fumigation was found to activate the MAPK signaling pathway that regulates a downstream network of transcription factors (TFs), including NAC, MYB, and WRKY TFs. This enhances both the ASA-GSH cycle and phenylpropanoid metabolism. This multi-level regulation promoted the accumulation of antioxidant metabolites (e.g., ascorbic acid and anthocyanins) and also contributed to the maintenance of cellular energy homeostasis. Our study provides the first evidence that plant essential oils modulate the antioxidant defense system in postharvest crops through the MAPK signaling pathway and provides a new potential strategy for the development of signal pathway-based green preservation technologies for harvested produce.