Overexpression and silent expression of CrGA20ox1 from Camellia reticulata 'Hentiangao' and its effect on morphological alterations in transgenic tobacco plants

Gibberellin 20-oxidase (GA20ox) is a multifunctional enzyme that is involved in the regulation of GA biosynthesis and the control of plant growth. We identified and characterized a GA20ox gene (CrGA20ox1) in Camellia reticulata 'Hentiangao'; subsequently, expression levels of CrGA20ox1 in four phenotypically different camellias were analysed using fluorescent quantitative real-time PCR (qRT-PCR). The results demonstrated that the CrGA20ox1 gene was expressed in all four camellias at various levels, indicating that the gene's expression intensity was positively associated with camellia height. In addition, phenotypic comparison among transgenic tobacco plants saw a nearly 3.6-fold increase in height of sense CrGA20ox1 lines as contrasted with wild-type tobacco. Interestingly and contrarily, the height of the transgenic plants expressing antisense CrGA20ox1 copies decreased by only around 0.5-fold of the controls' height. Endogenous hormone measurements illustrated that bioactive GA(4) predominantly increased in sense transgenic plants, whereas an obvious drop was observed in the antisense lines. Hence, overexpression of the CrGA20ox1 gene could accelerate vegetative growth; however, silent expression of the CrGA20ox1 gene impelled plants towards dwarfism.