OVEREXPRESSION OF THE GIBBERELLIN 20-OXIDASE OR GIBBERELLIN 3-OXIDASE GENE FROM TORENIA FOURNIERI AFFECTING PLANT MORPHOLOGY IN TRANSGENIC TRICYRTIS SP.
Gibberellins (GAs) are plant hormones controlling many aspects of plant growth and development including stem elongation, germination and transition from vegetative growth to flowering. GA 20-oxidase (GA 20ox) and GA 3-oxidase (GA 3ox), classes of 2-oxoglutarate-dependent dioxygenases, catalyze the conversion of precursor GAs to their bioactive forms, and therefore play a direct role in determining the levels of bioactive GAs in plants. Transgenic plants of the liliaceous ornamental Tricyrtis sp. Shinonome overexpressing the GA 20ox or GA 3ox gene from Torenia fournieri (TfGA20ox2 and TfGA3ox1) were produced. After 3 years of cultivation, 4 and 2 independent transgenic plants containing TfGA20ox2 and TfGA3ox1, respectively, were subjected to morphological characterization at the flowering stage. Because GA 20ox and GA 3ox catalyze the last step in the formation of bioactive GAs, overexpression of TfGA20ox2 or TfGA3ox1 was initially expected to induce a GA-overproduction phenotype in transgenic plants, such as internode elongation. However, on the contrary, all the transgenic plants exhibited reduced plant height, reduced internode length and reduced stem diameter compared with the control, non-transgenic plants, irrespective of the kind of transgene. In addition, all the transgenic plants had slender leaves and narrow flower tepals. Exogenous treatment of transgenic plants with gibberellic acid and a GA biosynthesis inhibitor, uniconazol, resulted in increased and decreased plant height, respectively. Possible factors leading to morphological alterations, observed in the present study, of transgenic Tricyrtis sp. were proposed.
Otani, M., Meguro, S., Gondaira, H., Hayashi, M., Saito, M., Han , D.S., Nakano, M., Mori, S., Li, T., Niki, T., Nishijima , T. and Koshioka, M. (2014). OVEREXPRESSION OF THE GIBBERELLIN 20-OXIDASE OR GIBBERELLIN 3-OXIDASE GENE FROM TORENIA FOURNIERI AFFECTING PLANT MORPHOLOGY IN TRANSGENIC TRICYRTIS SP.. Acta Hortic. 1025, 23-30
GA biosynthetic pathway, liliaceous ornamental plant, transgenic plant, morphological alteration