Effect of defoliation and wounding on expression of pectic polysaccharide-degrading enzyme genes in immature 'Hiratanenashi' persimmon fruit on the tree
Immature 'Hiratanenashi' persimmon (Diospyros kaki Thunb.) fruit soften rapidly on the tree after wounding, concomitant with ethylene production. Defoliation promotes the progress of fruit softening and expression of ethylene biosynthesis enzyme genes. To understand fruit softening on the tree in 'Hiratanenashi' persimmon, we analyzed expression of genes for two polygalacturonase (PG), one β-galactosidase (Gal), and one α-arabinofuranosidase (Arf) enzymes in persimmon fruit after wounding with or without defoliation. Wounding with defoliation accelerated fruit softening on the tree more than wounding without defoliation. DkPG1, DkPG2, DkGal1 and DkArf1 in pulp tissue were expressed at the basal level until four days after wounding without defoliation, but increased DkGal1 and DkArf1 expression in the core section of the fruit was observed at four days after wounding. There was a large increase in DkPG1, DkPG2, DkGal1 and DkArf1 expression after six days in both pulp and core sections of fruit. Wounding combined with defoliation induced DkPG2, DkGal1 and DkArf1 gene expression at two or four days after treatment in both pulp and core tissues; DkGal1 was most highly induced. These results suggest that attachment of leaves to the fruit-bearing shoot prevents fruit softening on the tree by delaying the degradation of polysaccharide side chains.
Nakatsuka, A., Sun, N., Esumi, T. and Itamura, H. (2018). Effect of defoliation and wounding on expression of pectic polysaccharide-degrading enzyme genes in immature 'Hiratanenashi' persimmon fruit on the tree. Acta Hortic. 1195, 239-242
β-galactosidase, Diospyros kaki, ethylene, fruit softening