Global changes in metabolic pathways in endocarp of "Dayagan" hybrid citrus fruit during segment drying revealed by widely targeted metabolomics and transcriptomics analysis.

Segment drying is a severe physiological disorder of citrus fruit that occurs during on-tree and postharvest storage. Although many research have focused on the analysis of metabolic pathways in juice vesicles during segment drying, the associated changes in endocarp are poorly understood. Physiological analysis, widely targeted metabolomics, and transcriptomics were utilized to systematically compare the changes in endocarp between normal and disordered fruit affected by segment drying in "Dayagan" hybrid citrus. Physiological analysis showed that segment drying was associated with modification of phenotype, increase in cell wall components contents, and decrease in pectin degradation enzymes activities. Metabolomic profiling identified a total of 951 differentially accumulated metabolites upon segment drying. These metabolites were enriched in metabolic pathways relating to the synthesis of amino acids and derivatives, lipids, and flavonoids. Transcriptomics analysis revealed 6103 genes that were differentially expressed during segment drying, with increased expression of phenylpropanoid pathway genes and cell wall...