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

• Published in: Journal of plant physiology 2013-11, Vol.170 (16), p.1416-1423
• Main Authors: Otani, Masahiro, Meguro, Shuhei, Gondaira, Haruka, Hayashi, Megumi, Saito, Misaki, Han, Dong-Sheng, Inthima, Phithak, Supaibulwatana, Kanyaratt, Mori, Shiro, Jikumaru, Yusuke, Kamiya, Yuji, Li, Tuoping, Niki, Tomoya, Nishijima, Takaaki, Koshioka, Masaji, Nakano, Masaru
• Format: Article
• Language: English
• Subjects: Agrobacterium - genetics; bioactive properties; biochemical pathways; Breeding; Chromatography, Liquid; Correlation analysis; engineering; Enzymes; flowers; Flowers - genetics; Flowers - growth & development; Gene Expression Regulation, Developmental; Gene Expression Regulation, Plant; gene overexpression; Genes; Gibberellic acid; Gibberellin metabolic pathway; Gibberellins; Gibberellins - administration & dosage; Gibberellins - metabolism; growth and development; Japan; Lamiaceae - genetics; leaves; Liliaceae - genetics; Liliaceae - growth & development; Liliaceous ornamental plant; Mass Spectrometry; Microscopy, Electron, Scanning; Mixed Function Oxygenases - genetics; Mixed Function Oxygenases - metabolism; Morphological alteration; ornamental plants; Pathways; phenotype; plant architecture; plant breeding; Plant Leaves - genetics; Plant Leaves - growth & development; Plant Proteins - genetics; Plant Proteins - metabolism; Plants (organisms); Plants, Genetically Modified - genetics; Plants, Genetically Modified - growth & development; Polymerase Chain Reaction; reverse transcriptase polymerase chain reaction; shoots; signal transduction; spectroscopy; stem elongation; Torenia fournieri; Transformation, Genetic; Transgenic; Transgenic plant; transgenic plants; Tricyrtis
• ISSN: 0176-1617; 1618-1328
• DOI: 10.1016/j.jplph.2013.05.002

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.