Gibberellin 20-Oxidase Gene OsGA20ox3 Regulates Plant Stature and Disease Development in Rice

Abstract

Gibberellin (GA) 20-oxidase (GA20ox) catalyses consecutive steps of oxidation in the late part of the GA biosynthetic pathway. A T-DNA insertion mutant (17S-14) in rice, with an elongated phenotype, was isolated. Analysis of the flanking sequences of the T-DNA insertion site revealed that an incomplete T-DNA integration resulted in enhanced constitutively expression of downstream OsGA20ox3 in the mutant. The accumulation of bioactive GA(1) and GA(4) were increased in the mutant in comparison with the wild-type plant. Transgenic plants overexpressing OsGA20ox3 showed phenotypes similar to those of the 17S-14 mutant, and the RNA interference (RNAi) lines that had decreased OsGA20ox3 expression exhibited a semidwarf phenotype. Expression of OsGA20ox3 was detected in the leaves and roots of young seedlings, immature panicles, anthers, and pollens, based on β-glucuronidase (GUS) activity staining in transgenic plants expressing the OsGA20ox3 promoter fused to the GUS gene. The OsGA20ox3 RNAi lines showed enhanced resistance against rice pathogens Magnaporthe oryzae (causing rice blast) and Xanthomonas oryzae pv. oryzae (causing bacterial blight) and increased expression of defense-related genes. Conversely, OsGA20ox3-overexpressing plants were more susceptible to these pathogens comparing with the wild-type plants. The susceptibility of wild-type plants to X. oryzae pv. oryzae was increased by exogenous application of GA(3) and decreased by S-3307 treatment. Together, the results provide direct evidence for a critical role of OsGA20ox3 in regulating not only plant stature but also disease resistance in rice.

The DELLA Protein SLR1 Integrates and Amplifies Salicylic Acid- and Jasmonic Acid-Dependent Innate Immunity in Rice

“…Leaves of 6-weekold plants were sprayed until runoff with 100 mM GA 3 and/or 100 mM MeJA and 500 mM benzothiadiazole (BTH), a synthetic SA analog, and 3 d later, inoculated with Xoo using the leaf-clipping method. As shown in Figure 5A and consistent with previous findings (Yang et al, 2008;Yamada et al, 2012;Qin et al, 2013), BTH and MeJA pretreatment significantly increased basal leaf blight resistance compared to control, nontreated plants, whereas GA 3 application resulted in enhanced disease susceptibility (Fig. 5A).…”

“…oryzae (Xoo) and M. oryzae, causal agents of bacterial leaf blight and rice blast diseases, respectively Yang et al, 2008;Qin et al, 2013). However, no studies to date have addressed the importance of SLR1, the only DELLA protein in rice, in the resistance against these pathogens.…”

Intervention of Phytohormone Pathways by Pathogen Effectors

“…Thus, the GA-insensitive dwarf mutant gid1, which hyperaccumulates endogenous GA shows increased susceptibility to the rice blast fungus Pyricularia grisea (Tanaka et al, 2006), whereas rice plants compromised in GA biosynthesis show increased resistance to M. oryzae and X. o. pv oryzae (Qin et al, 2013). GAs produced as secondary metabolites in the rice-infecting pathogenic fungus Fusarium fujikuroi are well known examples of phytohormone mimics (Bömke and Tudzynski, 2009).…”

Recombinant DNA modification of gibberellin metabolism alters growth rate and biomass allocation in Populus

“…GA20ox overexpression has been used to successfully modify plant stature in Arabidopsis thaliana (Arabidopsis) ( AtGA20o x1 ; Pd GA2 0ox 1), Sola nu m tube ro sum (StGA20ox1), tobacco (NtGA20ox1), hybrid aspen (PtGA20ox1; PdGA20ox1), Carrizo citrange (CcGA20ox1) ( reviewed by Bhattacharya et al 2009;Jeon et al 2015), tomato (CcGA20ox1) (García-Hurtado et al 2012), rice (OsGA20ox3; Qin et al 2013), and Tricyrtis sp. 'Shinonome' (TfGA20ox2; Otani et al 2014).…”