Multi-omics analysis provided insights into the fruit softening of postharvest okra under carboxymethyl chitosan...

To understand the potential regulatory mechanism of carboxymethyl chitosan (CMCS) treatment on postharvest softening of okra, a joint analysis of physiologic index, transcriptome and metabolome was used. The results showed that CMCS could delay the deterioration of the apparent quality of okra and reduce the degradation of chlorophyll. CMCS can reduce the accumulation of WSP and CSP and the decrease of NSP, and inhibit the enzyme activities of pectin degradation (PE, PG, PL). The results of metabolic pathways related to quality and texture showed that CMCS could increase the metabolic level of pentose phosphate pathway (PPP), inhibit the expression of membrane lipid degradation-related genes, and balance the expression of antioxidant-related genes. Ethylene and abscisic acid (ABA) are two important phytohormones. CMCS down-regulates the biosynthesis of ethylene and increases the expression of ABA. The combined analysis of transcriptome and metabolome showed that CMCS could significantly up-regulate flavonoid biosynthesis metabolites and transcriptional expression levels. Cellulose and pectin are important polymers to maintain the rigidity of okra cell wall. CMCS treatment can slow down the accumulation of cellulose by regulating the expression of DEGs related to cellulose synthesis (CesA) and degradation (EGase). CMCS slowed down the degradation of pectin by down-regulating the expression of pectin degradation-related genes. These results indicate that the quality of okra is deteriorated and the fruit is softened during cold storage. CMCS treatment can improve the nutritional quality of okra and slow down its texture decline. In this study, the regulatory effect of CMCS on softening and quality deterioration of okra during cold storage was discussed at the molecular level, which provided a reference for improving the quality of postharvest okra.