Endo Tomoko, Shimada Takehiko, Fujii Hiroshi, Kobayashi Yasushi, Araki Takashi, Omura Mitsuo
Department of Citrus Research, National Institute of Fruit Tree Science, National Agricultural Research Organization, Shizuoka, Okitsu Shimizu-ku 424-0292, Japan.
Transgenic Res. 2005 Oct;14(5):703-12. doi: 10.1007/s11248-005-6632-3.
Citrus FT (CiFT) cDNA, which promoted the transition from the vegetative to the reproductive phase in Arabidopsis thaliana, when constitutively expressed was introduced into trifoliate orange (Poncirus trifoliata L. Raf.). The transgenic plants in which CiFT was expressed constitutively showed early flowering, fruiting, and characteristic morphological changes. They started to flower as early as 12 weeks after transfer to a greenhouse, whereas wild-type plants usually have a long juvenile period of several years. Most of the transgenic flowers developed on leafy inflorescences, apparently in place of thorns; however, wild-type adult trifoliate orange usually develops solitary flowers in the axils of leaves. All of the transgenic lines accumulated CiFT mRNA in their shoots, but there were variations in the accumulation level. The transgenic lines showed variation in phenotypes, such as time to first flowering and tree shape. In F(1) progeny obtained by crossing 'Kiyomi' tangor (C. unshiu x sinensis) with the pollen of one transgenic line, extremely early flowering immediately after germination was observed. The transgene segregated in F(1) progeny in a Mendelian fashion, with complete co-segregation of the transgene and the early flowering phenotype. These results showed that constitutive expression of CiFT can reduce the generation time in trifoliate orange.
柑橘成花素（CiFT）的互补DNA（cDNA）在拟南芥中持续表达时可促进其从营养生长阶段向生殖生长阶段的转变，将其导入枳橙（Poncirus trifoliata L. Raf.）中。持续表达CiFT的转基因植株表现出早花、早结果以及特征性的形态变化。它们在转移到温室后最早12周就开始开花，而野生型植株通常有长达数年的幼年期。大多数转基因花在叶状花序上发育，明显取代了刺；然而，野生型成年枳橙通常在叶腋处发育单花。所有转基因株系的嫩枝中都积累了CiFT信使核糖核酸（mRNA），但积累水平存在差异。转基因株系在表型上存在差异，如首次开花时间和树形。在用“清见”橘橙（C. unshiu x sinensis）与一个转基因株系的花粉杂交获得的F(1)代子代中，观察到种子萌发后立即出现极早开花现象。转基因在F(1)代子代中以孟德尔方式分离，转基因与早花表型完全共分离。这些结果表明，CiFT的持续表达可以缩短枳橙的世代时间。
