Integrated transcriptome and proteome analysis reveals the regulatory mechanisms of citric acid and L-Cysteine treatment in mitigating browning and senescence of postharvest litchi fruit

Abstract

Litchi is susceptible to browning and senescence after harvest, with a short shelf-life of only 2 days at room temperature. Our study optimized a preservative treatment (1% citric acid and 1g L⁻¹ L-cysteine), significantly enhanced the storage quality and extended the shelf-life of litchi fruit by 4–6 days. This treatment effectively reduced the respiration rate, decay rate, and browning degree of litchi fruit, lowered the level of malondialdehyde, protein carbonylation, and H₂O₂, as well as the activities of polyphenol oxidase (PPO), peroxidase (POD), and laccase (Lac) of litchi pericarp, while maintained the total soluble solids (TSS) and VC content of litchi pulp. Transcriptome and proteome analyses showed the treatment modulated oxidation-reduction system, phenylpropanoid and flavonoid biosynthesis pathways, fungal inhibition, and cell wall metabolism. Specifically, it promoted ascorbate peroxidase (APX) and superoxide dismutase (SOD) activity, maintained anthocyanin and total phenols (TPs) contents, improved the gene and protein expression levels of glutathione transferase (GST), L-ascorbate oxidase (AAO), FAD-binding proteins, dirigent proteins (DIRs), chitinases, cytochrome P450, and others. Our research presents an improved method to extend litchi fruit's shelf-life at room temperature and a theoretical foundation for further preservation mechanism studies.