Integrated metabolomics and transcriptomics reveal that role of L-pyroglutamic acid in alleviating eggplant pericarp shrinkage

LPA treatment alleviates eggplant pericarp shrinkage. • The biosynthesis of functional amino acids depresses pericarp shrinkage. • The maintenance of TCA cycle decreases pericarp shrinkage. • The activation of linoleic acid metabolism lowers pericarp shrinkage under enhanced antioxidant capacity. • The enhancement of cell wall rigidity and hydrophobicity reduces pericarp shrinkage. Eggplant is prone to pericarp shrinkage during room-temperature storage, reducing its commercial value. While L -pyroglutamic acid (LPA), a glutathione cycle derivative, shows potential in post-harvest preservation, its exact mechanisms in eggplant post-harvest storage remain unclear. This study found that LPA treatment alleviated pericarp shrinkage and darkening, reduced water loss, and maintained the contents of nutrients (soluble sugar, soluble protein, and amino acid) in eggplant. Through integrated transcriptomic, metabolomic, physiological, and biochemical analyses, we elucidated the regulatory effects of LPA. LPA promoted the biosynthesis of osmoregulatory and resistance-related amino acids, such as proline, glutamate, arginine, and glutamine. LPA enhanced the accumulation of citrate, stimulated the TCA cycle, and regulated energy supply. Additionally, LPA activated linoleic acid metabolism, leading to the oxidation of linoleic acid by lipoxygenase to produce oxylipins, including 9(S)-HPODE, 9-OxoODE, and 13(S)-HODE. Under the buffering effect of the antioxidant system, these oxylipins may act as defense signal activators, enhancing fruit defense capacity. Furthermore, LPA enhanced the mechanical strength and hydrophobicity of the cell wall by promoting the accumulation of polysaccharides, including cellulose, hemicellulose, pectin, and lignin, thereby reinforcing the epidermal barrier function. This study elucidates the molecular mechanisms by which LPA maintains post-harvest eggplant quality through the regulation of primary metabolism, defense signaling, and cell wall barrier, providing a theoretical basis for its application in fruit and vegetable preservation.