Characteristic changes in cell wall metabolism and related gene expression in different parts of Tarocco blood orange pulp during cold storage

Tarocco blood orange is mainly famous for easy mastication. Mastication is the most important quality attribute contributed or determined by parenchyma cell walls, which consisted of a mixture of pectin, lignin, and cellulose. However, there were few studies associated with the components of cell wall for blood orange during cold storage at present. In the present study, the protopectin content first increased and then decreased, the contents of soluble pectin, lignin and cellulose showed an increasing trend, and the activities of PME, POD and cellulase were consistent with the corresponding changes described above in the three pulp parts during cold storage. Therefore, the easy mastication of blood orange may be attributed to the decreased content of protopectin and increased content of water-soluble pectin during cold storage. Regarding the expression of genes related to pectin, lignin and cellulose metabolism, the upregulated genes PE11, PE17, PE18 and PL5 for pectin metabolism, POD1, POD40, POD55 and LAC15 for lignin accumulation and the downregulated genes EG17 and RLSK8 for cellulose, showed the greatest contributions to the changes of above-mentioned cell wall components during cold storage.