Functional Analysis of the Gene Family in Peach.

Peach ( L. Batsch) trees grow vigorously and are subject to intense pruning during orchard cultivation. Reducing the levels of endogenous gibberellins (GAs) represents an effective method for controlling branch growth. Gibberellin 2-oxidases (GA2oxs) deactivate bioactive GAs, but little is known about the GA2ox gene family in peach. In this study, we identified seven genes in the peach genome, which were clustered into three subgroups: C-GA2ox-I, C-GA2ox-II, and C-GA2ox-I. Overexpressing representative genes from the three subgroups, , , and , in tobacco resulted in dwarf plants with shorter stems and smaller leaves than the wild type. An analysis of the GA metabolic profiles of the transgenic plants showed that PpGA2ox-5 (a member of subgroup C-GA2ox-II) is simultaneously active against both C-GAs and C-GAs,which implied that C-GA2ox-II enzymes represent intermediates of C-GA2oxs and C-GA2oxs. Exogenous GA treatment of shoot tips activated the expression of all seven genes, with different response times: the - genes were transcriptionally activated more rapidly than the genes. GA metabolic profile analysis suggested that C-GA2ox depletes GA levels more broadly than C-GA2ox. These results suggest that the gene family is responsible for fine-tuning endogenous GA levels in peach. Our findings provide a theoretical basis for appropriately controlling the vigorous growth of peach trees.