Multi-omics analysis revealed room temperature storage affected the quality of litchi by altering carbohydrate metabolism

Litchi (Litchi chinensis Sonn.) fruit easily deteriorates and has a short storage life. Room temperature storage is widely used during short-distance transportation and sale of litchi fruits. This study explored the changes in the quality of litchi pulp at room temperature storage using transcriptomics, proteomics, and metabolomics analyses. The results illustrated significant changes in carbohydrate metabolism pathways. Increases in d-ribose-5-phosphate, d-ribose, d-mannose-6-phosphate, d-mannose, d-mannitol, D-sorbitol, and d-fructose-1-phosphate indicated that fructose and mannose metabolism, the pentose phosphate pathway, and amino sugar and nucleotide sugar metabolism competed with glycolysis for α-d-glucose, α-d-glucose-6-phosphate, and β-d-fructose-6-phosphate. Citrate and l-malic acid from the tricarboxylic acid cycle (TCA cycle) might be consumed via the biosynthesis of amino acids and lipids. Most of the differentially expressed genes and proteins related to glycolysis and the TCA cycle were downregulated, which verified that these two pathways were impeded. Flow direction changes in glycolysis and the TCA cycle might lead to energy deficiency. Upregulated activities of α-amylase and soluble acid invertase cleaved starch and sucrose into glucose and fructose, which replenished deficient energy metabolism substrates. During these processes, the changes in the content and composition of sugar and acid result in a decrease in flavor. Additionally, the polysaccharide degradation softened the texture and reduced the nutritional value. By systematically exploring the regulation of physiological changes in the pulp of litchi fruit stored at room temperature, we provid a basis for optimizing the preservation of litchi fruit and a reference for studying fruit carbohydrate metabolism.