Physicochemical and molecular analysis of cell wall metabolism between two navel oranges (Citrus sinensis) with different mastication traits

Abstract

FJ72-1 navel orange and its bud mutant FJWC exhibit differences in melting texture character which are influenced mostly by cell wall metabolism. Here we compared the contents of water soluble pectin (WSP), protopectin, total pectin (TP), cellulose, and hemicellulose, activities of polygalaturonase (PG), pectin methylesterase (PME), pectate lyases (PL), cellulase (Cel) and gene expression levels of PG, PME, PL and Cel between the two cultivars. The content of cellulose and hemicellulose decreased progressively during fruit ripening. At the harvest time (230 DAF), the content of cellulose and hemicellulose in FJWC were obviously higher than those in FJ72-1; the WSP content, PG activities and its gene expression level in FJWC was lower than those in FJ72-1. Moreover, gene expression levels of PME and Cel in FJWC were only one-quarter of those in FJ72-1 at 230 DAF. The present work showed that the inferior melting character of FJWC attributed to the lower WSP, higher TP or protopectins, higher cellulose and hemicellulose than those in the pulp of FJ72-1 at harvest time. Lower expression levels of PG, PME and Cel at harvest time might be associated with the inferior melting character.