Huang Haijiao, Wang Shan, Jiang Jing, Liu Guifeng, Li Huiyu, Chen Su, Xu Huanwen
State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, 26 Hexing Road, Harbin, 150040, China.
Physiol Plant. 2014 Aug;151(4):495-506. doi: 10.1111/ppl.12123. Epub 2014 Jan 29.
The involvement of APETALA1 (AP1) in the flowering transition has been the focus of much research. Here, we produced Betula platyphylla × Betula pendula (birch) lines that overexpressed BpAP1 using Agrobacterium-mediated transformation; we obtained five independent 35S::BpAP1 transgenic lines. Polymerase chain reaction (PCR), Southern, northern and western analyses were used to identify the transformants. As determined by quantitative real-time PCR (qRT-PCR), BpAP1 expression in roots, shoots, leaves and terminal buds of 35S::BpAP1 transgenic lines was significantly higher than that in the wild type (WT, P < 0.01). The average height of 2-year-old 35S::BpAP1 plants was significantly lower (41.17%) than that of non-transgenic plants. In the 35S::BpAP1 lines, inflorescences emerged successively beginning 2 months after transplanting. In addition, the length-diameter ratio of fully developed male and female inflorescences were both significantly less than those of the WT (P < 0.05), i.e. the morphological characteristic was stubby. The male inflorescences emerged early, with empty, draped anthers, and pollen was rarely produced, whereas the female floret structure was not different from WT. The pistils developed normally and could accept pollen, leading to the production of hybrid progeny (F1 ). F1 plants completed flowering within only 1 year after sowing. We demonstrate that BpAP1 can be inherited through sexual reproduction. Overexpression of BpAP1 caused early flowering and dwarfism; these lines had an obviously shortened juvenile phase. These results greatly increase our understanding of the mechanisms underlying the flowering transition and enhance genetic studies of birch traits, and they open up new possibilities for the breeding of birch and other woody plants.
APETALA1（AP1）在开花转变过程中的作用一直是众多研究的焦点。在此，我们利用农杆菌介导的转化方法培育了过表达BpAP1的白桦（Betula platyphylla×Betula pendula）株系；我们获得了5个独立的35S::BpAP1转基因株系。采用聚合酶链反应（PCR）、Southern杂交、Northern杂交和Western分析来鉴定转化体。通过定量实时PCR（qRT-PCR）测定，35S::BpAP1转基因株系的根、茎、叶和顶芽中BpAP1的表达显著高于野生型（WT，P<0.01）。2年生35S::BpAP1植株的平均高度显著低于非转基因植株（降低了41.17%）。在35S::BpAP1株系中，移栽后2个月开始陆续出现花序。此外，完全发育的雄花序和雌花序的长宽比均显著小于野生型（P<0.05），即形态特征粗短。雄花序出现较早，花药空瘪、下垂，很少产生花粉，而雌小花结构与野生型无差异。雌蕊发育正常，能够接受花粉，从而产生杂交后代（F1）。F1植株播种后仅1年内就完成了开花。我们证明BpAP1可以通过有性繁殖遗传。BpAP1的过表达导致早花和矮化；这些株系的幼年期明显缩短。这些结果极大地增进了我们对开花转变潜在机制的理解，加强了白桦性状的遗传研究，并为白桦及其他木本植物的育种开辟了新的可能性。
