Overexpression of Jatropha Gibberellin 2-oxidase 6 (JcGA2ox6) Induces Dwarfism and Smaller Leaves, Flowers and Fruits in Arabidopsis and Jatropha

Abstract

Gibberellins (GAs) are plant hormones that play fundamental roles in plant growth and development. Gibberellin 2-oxidase (GA2ox) plays a direct role in determining the levels of bioactive GAs by catalyzing bioactive GAs or their immediate precursors to inactive forms. In this study, a GA2ox gene, designated JcGA2ox6, was isolated from Jatropha curcas. JcGA2ox6 is expressed in all tissues of adult Jatropha, with the highest expression level in male flowers and the lowest expression level in young leaves. Overexpression of JcGA2ox6 in Arabidopsis resulted in a typical dwarf phenotype, along with late flowering, smaller leaves and flowers, shorter siliques and smaller seeds. Similarly, when JcGA2ox6 was overexpressed in Jatropha, the transgenic plants exhibited a dwarf phenotype with dark-green leaves and smaller inflorescences, flowers, fruits and seeds. However, the flowering time of Jatropha was not affected by overexpression of JcGA2ox6, unlike that in the transgenic Arabidopsis. Moreover, the number of flowers per inflorescence, the weight of 10 seeds and the seed oil content were significantly decreased in transgenic Jatropha. The results indicated that overexpression of JcGA2ox6 had a great impact on the vegetative and reproductive growth of transgenic Jatropha. Furthermore, we found that the dwarf phenotype of transgenic Jatropha was caused by a decrease in endogenous bioactive GA4, which was correlated with the degree of dwarfism.

Analysis of Transcriptional Responses of the Inflorescence Meristems in Jatropha curcas Following Gibberellin Treatment

“…In GAs biosynthesis and catabolism pathways, the bioactive GAs, including GA 1 and GA 4 , could be catalyzed by GA 20-oxidases (GA20OX) and GA 3-oxidases (GA3OX), but the bioactive GAs can be converted to inactive forms by GA 2-oxidases (GA2OX) [ 11 ]. The number of flowers could be decreased by the overexpression of JcGA2OX6 in J. curcas [ 12 ].DELLA proteins were nuclear negative regulators to repress GA signaling. The GAs receptor, GID1 (GA Insensitive Dwarf 1), could achieve GAs signaling transduction by degrading DELLA proteins [ 13 ].…”

The HDA19 histone deacetylase complex is involved in the regulation of flowering time in a photoperiod‐dependent manner

“…The expression of GASA5 and GA2OX6 was significantly upregulated in both the hdc1 and hda19 mutants, but not in the hda6 mutant (Figure e). Overexpression of GASA5 and GA2OX6 was shown to cause late flowering in the wild‐type background (Zhang et al ., ; Hu et al ., ). Thus, the late‐flowering phenotype of the hdc1 and hda19 mutants is at least partially caused by the upregulation of GASA5 and GA2OX6 .…”

“…The flowering repressors GASA5 and GA2OX6 are known to be negative regulators of the gibberellin signaling pathway (Zhang et al ., ; Hu et al ., ). To confirm that HDC1 is involved in the regulation of flowering time through the gibberellin signaling pathway, we treated the wild‐type and hdc1 mutant plants with Gibberellin A3 (GA3) to determine whether the effect of hdc1 on flowering time is related to the gibberellin signaling pathway.…”

Systematic Analysis of Gibberellin Pathway Components in Medicago truncatula Reveals the Potential Application of Gibberellin in Biomass Improvement

“…Furthermore, GA3ox also participates in the synthesis of bioactive GAs and the ga3ox1 ga3ox2 double mutants display defects in shoot and root development [ 15 ]. Similar to the ga20ox and ga3ox mutants, overexpression of BnGA2ox6 and JcGA2ox6 in Arabidopsis results in GA-deficiency phenotypes, including late flowering, smaller leaves, and shorter siliques [ 16 , 17 ]. However, ectopic overexpression of the AtGA20ox1 gene in hybrid aspen results in trees with longer xylem fibers, larger leaves, and increased biomass [ 18 ].…”