Integrated transcriptomics, proteomics, and metabolomics analysis reveals the mechanism of litchi pulp deterioration during long-term cold storage

Litchi (Litchi chinensis Sonn.) fruit is delicious and nutritious but has a short storage life. Cold storage is widely used in the litchi industry as the most efficient preservation method for litchi fruit. In this study, comparative analyses of the transcriptomics, proteomics, and metabolomics of 0-d and 28-d litchi pulp were revealed the mechanism underlying litchi pulp deterioration during long-term cold storage. The results indicated that long-term cold storage might maintain the appearance of litchi fruit, but it cannot ensure the quality of the pulp. The differential genes, proteins, and metabolites were primarily involved in the metabolism of amino acids, nucleic acids, lipids, and secondary metabolites, which are regulated by transcription and translation. However, the changes in the gene, protein, and metabolite levels were inconsistent. The metabolic pathways of 28-d pulp were imbalanced because of the degradation of sugars, organic acids, amino acids, and nucleotides, as well as the synthesis of lipids and secondary metabolites. The 28-d pulp was primarily stressed by cold and disease; it resisted these stresses by accumulating resistance proteins, strengthening and maintaining the cell wall and cell membrane structure, and synthesizing secondary metabolites. The deficiencies in energy metabolism substrates and synthesized ATP of 28-d pulp hindered its ability to support life activities and stress resistance. Therefore, the litchi pulp could not maintain regular metabolism, stress resistance, energy supply, and exhibited deteriorated pulp quality during long-term cold storage. This study provides new insights into the effect of cold storage in preserving litchi fruit.