Functional Analysis of the Gibberellin 2-oxidase Gene Family in Peach

Abstract

Peach (<i>Prunus persica</i> 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 <i>PpGA2ox</i> genes in the peach genome, which were clustered into three subgroups: C₁₉-GA2ox-I, C₁₉-GA2ox-II, and C₂₀-GA2ox-I. Overexpressing representative genes from the three subgroups, <i>PpGA2ox-1</i>, <i>PpGA2ox-5</i>, and <i>PpGA2ox-2</i>, 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 C₁₉-GA2ox-II) is simultaneously active against both C₁₉-GAs and C₂₀-GAs,which implied that C₁₉-GA2ox-II enzymes represent intermediates of C₁₉-GA2oxs and C₂₀-GA2oxs. Exogenous GA₃ treatment of shoot tips activated the expression of all seven <i>PpGA2ox</i> genes, with different response times: the <i>C</i> ₁₉-<i>GA2ox</i> genes were transcriptionally activated more rapidly than the <i>C₂₀-GA2ox</i> genes. GA metabolic profile analysis suggested that C₂₀-GA2ox depletes GA levels more broadly than C₁₉-GA2ox. These results suggest that the <i>PpGA2ox</i> 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.