The gibberellin content of rolA transgenic tobacco plants is specifically altered

Transgenic tobacco plants (Nicotiana tabacum L.) that express the rolA gene of Agrobacterium rhizogenes TL-DNA are dwarfs with wrinkled leaves. The concentration of gibberellin A(1), determined by gas chromatography-mass spectrometry, was reduced by up to 40% in both the apical shoot and young leaves of rolA transgenics compared with wild-type. The GA(20) concentration was reduced to a similar extent. In contrast, the concentrations of the metabolic precursors GA(53) and GA(19) were significantly increased. These changes were positively correlated with the strength of rolA gene expression. The results indicate a metabolic block of the conversion of GA(19) to GA(20), a reaction mediated by GA(20)-oxidase, and suggests that the reduction in biologically active GA(1) is causally related to the rolA phenotype.