Overexpression of the gibberellin 2-oxidase gene from Torenia fournieri induces dwarf phenotypes in the liliaceous monocotyledon Tricyrtis sp

Gibberellins (GAs) are the plant hormones that control many aspects of plant growth and development, including stem elongation. Genes encoding enzymes related to the GA biosynthetic and metabolic pathway have been isolated and characterized in many plant species. Gibberellin 2-oxidase (GA2ox) catalyzes bioactive GAs or their immediate precursors to inactive forms; therefore, playing a direct role in determining the levels of bioactive GAs. In the present study, we produced transgenic plants of the liliaceous monocotyledon Tricyrtis sp. overexpressing the GA2ox gene from the linderniaceous dicotyledon Torenia fournieri (TfGA2ox2). All six transgenic plants exhibited dwarf phenotypes, and they could be classified into two classes according to the degree of dwarfism: three plants were moderately dwarf and three were severely dwarf. All of the transgenic plants had small or no flowers, and smaller, rounder and darker green leaves. Quantitative real-time reverse transcription-polymerase chain reaction (PCR) analysis showed that the TfGA2ox2 expression level generally correlated with the degree of dwarfism. The endogenous levels of bioactive GAs, GA1 and GA4, largely decreased in transgenic plants as shown by liquid chromatography-mass spectrometry (LC-MS) analysis, and the level also correlated with the degree of dwarfism. Exogenous treatment of transgenic plants with gibberellic acid (GA3) resulted in an increased shoot length, indicating that the GA signaling pathway might normally function in transgenic plants. Thus, morphological changes in transgenic plants may result from a decrease in the endogenous levels of bioactive GAs. Finally, a possibility of molecular breeding for plant form alteration in liliaceous ornamental plants by genetically engineering the GA metabolic pathway is discussed.

Electroporation of rapeseed protoplasts - transient and stable transformation

Protoplasts of Brassica napus hypocotyls were transfected using electroporation. Parameters such as discharge potential, protoplast density and buffer constituents were tested to determine the most suitable conditions for gene transfer. To monitor the introduction of DNA into protoplasts a plasmid containing the β-glucuronidase (EC 3.2.1.31), and the neomycin phospotransferase (EC 2.7.1.95) genes was used. By using this construct, expression of a screenable marker gene for transient expression analysis as well as an antibiotic resistance marker gene for selection of stable transformants were obtained. Refined electroporation conditions resulted in a frequency of 0.1% transiently transformed protoplasts. Microcalluses were cultured under selective conditions in a bead-type culture system. Resistant callus, with an absolute transformation frequency of 4.9 × 10^-5 and a relative transformation frequency of 0.3% could be achieved. X-ray irradiation of newly electroporated protoplasts did not enhance absolute transformation frequencies. From some of the resistant calluses, transgenic plants could be regenerated which were characterized by molecular analysis.