Effect of defoliation and wounding on expression of pectic polysaccharide-degrading enzyme genes in immature 'Hiratanenashi' persimmon fruit on the tree

摘要

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 B-galactosidase (Gal), and one a-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. DkPGl, DkPG2, DkGall and DkArfl in pulp tissue were expressed at the basal level until four days after wounding without defoliation, but increased DkGall and DkArfl expression in the core section of the fruit was observed at four days after wounding. There was a large increase in DkPGl, DkPG2, DkGall and DkArfl expression after six days in both pulp and core sections of fruit. Wounding combined with defoliation induced DkPG2, DkGall and DkArfl gene expression at two or four days after treatment in both pulp and core tissues; DkGall was most highly induced. These results suggest that attachment of leaves to the fruit-bearing shootprevents fruit softening on the tree by delaying the degradation of polysaccharide side chains.