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

Abstract

Peach (Prunus persica 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 PpGA2ox 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, PpGA2ox-1, PpGA2ox-5, and PpGA2ox-2, 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 PpGA2ox genes, with different response times: the C19-GA2ox genes were transcriptionally activated more rapidly than the C20-GA2ox genes. GA metabolic profile analysis suggested that C20-GA2ox depletes GA levels more broadly than C19-GA2ox. These results suggest that the PpGA2ox 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.

Physiological and Comparative Transcriptome Analyses of the High-Tillering Mutant mtn1 Reveal Regulatory Mechanisms in the Tillering of Centipedegrass (Eremochloa ophiuroides (Munro) Hack.)

“…Gibberellin 2-oxidases (GA2oxs) are important GA metabolism enzymes that reduce the GA content [ 35 , 36 , 37 ]. In this work, the expression level of GA2ox1 was upregulated in the mtn1 mutant.…”

Effects of gibberellins on important agronomic traits of horticultural plants

“…Editing PROCERA / SlDELLA in tomato and MaGA20ox2 in Musa acuminate (banana) using CRISPR-Cas9 results in shortened internodes (a dominant mutation and a loss-of-function mutation; Tomlinson et al., 2019 ; Shao et al., 2020 ). Overexpression of PsGA3ox1 and PpGA2ox1 lead to longer and more compact internodes in pea and Nicotiana tabacum (tobacco), respectively ( Reinecke et al., 2013 ; Cheng et al., 2021 ). GAs and PAC application also obviously change the internode length of two commercial grapevine cultivars ( Acheampong et al., 2015 ).…”

“…All of the genes discussed above ( Cla015407 , TIE1 , NHM1 , MaGA20ox2 , PsGA3ox1 , and PROCERA ) are classified into GA synthesis or signal genes directly influencing endogenous GA in tissues, and abnormal concentrations of endogenous GAs affect development of tissues, such as stem. We assume that this is also a conservative mechanism of horticultural species as in model plants where GAs positively regulate stem elongation ( Tomlinson et al., 2019 ; Shao et al., 2020 ; Cheng et al., 2021 ; Kou et al., 2021 ; Liu et al., 2022 ). Internode/stem is made up of millions of cells, and cell fate determines internode elongation.…”

“…GA biosynthesis in plants consists of a series of complicated oxidation-reduction reactions, including reactions from geranylgeranyl diphosphate (GGDP) to bioactive GAs ( Yamaguchi, 2008 ; Hedden, 2020 ). This process is usually classified into three stages in Arabidopsis ( Figure 1A ; Yamaguchi, 2008 ; Zhang et al., 2020 ; Cheng et al., 2021 ; Shohat et al., 2021 ). The first stage is the synthesis of GGDP to ent -kaurene using GGDP as starting material in plastids, which is consecutively catalyzed and oxidated by ent -copalyl diphosphate synthase (CPS) and ent -kaurene synthase (KS) ( Figure 1A ; Sun and Kamiya, 1997 ; Helliwel et al., 2001 ; Hedden, 2020 ).…”

The distribution of bioactive gibberellins along peach annual shoots is closely associated with PpGA20ox and PpGA2ox expression profiles

“…GA is the primary growth-promoting hormone of peach annual shoots, but the genes involved in biosynthesis and degradation are poorly understood. To properly regulate the growth of annual shoots, it is necessary to identify the genes that encode the enzymes that synthesize and deactivate GA. Our previous study identified seven PpGA2ox genes in peach [16]. The present study identifies the GA biosynthetic genes and analyzes their transcription levels as well as those of the deactivating PpGA2oxs in six internodes from the top to the bottom of peach shoots.…”