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

摘要

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 GA_(4), which was correlated with the degree of dwarfism.