Transgenic ‘Duncan’ grapefruit (Citrus paradisi Macf.) and ‘Valencia’ sweet orange (Citrus sinensis [L.] Osbeck) plants ectopically expressing C. sinensis (cv. Washington navel orange) APETALA1 (CsAP1) or LEAFY (CsLFY) genes under control of the Arabidopsis thaliana stress-inducible promoter AtRD29A flowered under non-inductive (warm temperature, well-watered) greenhouse conditions, whereas their wild-type (WT) counterparts did not. The transgenic plants that flowered exhibited no altered morphological features, except the lack of thorns characteristic of juvenile WT plants. The most precocious T0 line, ‘Duncan’ grapefruit (Dun134-3) expressing the CsAP1 gene, flowered and fruited when it was 4.5 years old and the T1 siblings from this line flowered and fruited when they were just over 18 months old. In contrast, T1 seedlings from three lines of ‘Duncan’ grapefruit expressing the CsLFY gene flowered within 3 months after germination, but were unable to support fruit development. Transcript levels of corresponding transgenes in leaves were not correlated with earliness of flowering. To further study the activity of AtRD29A, leaves from three ‘Carrizo’ citrange (C. sinensis × Poncirus trifoliata) rootstock seedlings transformed with the green fluorescent protein (GFP) gene under regulation of the AtRD29A promoter were subjected to drought stress or well-watered conditions. Expression of GFP was not stress-dependent, consistent with the observation of flowering of CsAP1 and CsLFY transgenic plants under non-inductive conditions. Taken together, the results suggest that AtRD29A is constitutively expressed in a citrus background. Despite the loss of control over flowering time, transgenic citrus lines ectopically expressing C. sinensis AP1 or LFY genes under control of the A. thaliana RD29A promoter exhibit precocious flowering, fruit development and viable transgenic seed formation. These transformed lines can be useful tools to reduce the time between generations to accelerate breeding.

转基因 'Duncan' 葡萄柚 ( Citrus paradisi Macf.) 和 'Valencia' 甜橙 ( Citrus sinensis [L.] Osbeck) 植物异位表达C. sinensis (cv. Washington navel orange) APETALA1 ( CsAP1 ) 或LEAFY ( CsLFY ) 基因拟南芥应激诱导启动子AtRD29A的控制在非诱导（温暖的温度，充分浇水）温室条件下开花，而它们的野生型（WT）对应物则没有。开花的转基因植物没有表现出改变的形态特征，除了幼年WT植物缺乏刺特征。最早熟的 T0 系，表达CsAP1基因的“邓肯”葡萄柚 (Dun134-3)，在 4.5 岁时开花结果，该品系的 T1 兄弟姐妹在刚刚超过 18 个月大时开花结果。相比之下，来自三个“邓肯”葡萄柚品系的 T1 幼苗表达CsLFY基因在发芽后3个月内开花，但不能支持果实发育。叶片中相应转基因的转录水平与开花的提前性无关。为了进一步研究 AtRD29A 的活性，在AtRD29A启动子的调控下，用绿色荧光蛋白 ( GFP ) 基因转化了三株'Carrizo' 柑桔 ( C. sinensis  ×  Poncirus trifoliata ) 砧木幼苗的叶子进行干旱胁迫或充分浇水。条件。GFP的表达不依赖于胁迫，与CsAP1和CsLFY的开花观察结果一致非诱导条件下的转基因植物。总之，结果表明AtRD29A在柑橘背景中组成型表达。尽管失去了对开花时间的控制，但在拟南芥 RD29A启动子控制下异位表达中华柑桔AP1或LFY基因的转基因柑橘品系表现出早熟开花、果实发育和可行的转基因种子形成。这些转化的品系可以成为减少世代之间时间以加速育种的有用工具。