Tao L, Wang X L, Guo M H, Zhang Y W
Genetika. 2015 Aug;51(8):905-14. doi: 10.7868/s0016675815080111.
Vernalization plays a key role in the bolting and flowering of Chinese cabbage (Brassica rapa L. ssp. pekinensis). Plants can switch from vegetative to reproductive growth and then bolt and flower under low temperature induction. The economic benefits of Chinese cabbage will decline significantly when the bolting happens before the vegetative body fully grows due to a lack of the edible value. It was found that continuous seedling breeding reduced the heading of Chinese cabbage and led to bolt and flower more easily. In the present study, two inbred lines, termed A161 and A105, were used as experiment materials. These two lines were subjected to vernalization and formed four types: seeds-seedling breeding once, seedling breeding twice, seedling breeding thrice and normal type. Differences in plant phenotype were compared. DNA methylation analysis was performed based on MSAP method. The differential fragments were cloned and analyzed by qPCR. Results showed that plants after seedling breeding thrice had a loosen heading leaves, elongated center axis and were easier to bolt and flower. It is suggested that continuous seedling breeding had a weaker winterness. It was observed that genome methylation level decreased with increasing generation. Four differential genes were identified, short for BraAPC1, BraEMP3, BraUBC26, and BraAL5. Fluorescent qPCR analysis showed that expression of four genes varied at different reproduction modes and different vernalization time. It is indicated that these genes might be involve in the development and regulation of bolting and flowering of plants. Herein, the molecular mechanism that continuous seedling breeding caused weaker winterness was analyzed preliminarily. It plays an important guiding significance for Chinese cabbage breeding.
春化作用在中国大白菜（Brassica rapa L. ssp. pekinensis）的抽薹开花过程中起着关键作用。植物在低温诱导下可从营养生长转变为生殖生长，进而抽薹开花。当大白菜在营养体未充分生长之前就发生抽薹时，由于缺乏食用价值，其经济效益将显著下降。研究发现，连续育苗会降低大白菜的结球率，并使其更容易抽薹开花。在本研究中，两个自交系A161和A105被用作实验材料。这两个自交系经过春化处理后形成了四种类型：种子-育苗一次、育苗两次、育苗三次和正常类型。比较了不同类型植株的表型差异。基于甲基化敏感扩增多态性（MSAP）方法进行了DNA甲基化分析。对差异片段进行克隆，并通过实时荧光定量PCR（qPCR）进行分析。结果表明，经过三次育苗的植株结球叶片松散，中心轴伸长，更容易抽薹开花。这表明连续育苗的冬性较弱。观察到随着世代增加，基因组甲基化水平降低。鉴定出四个差异基因，分别为BraAPC1、BraEMP3、BraUBC26和BraAL5。荧光定量PCR分析表明，这四个基因在不同繁殖方式和不同春化时间下表达存在差异。这表明这些基因可能参与了植物抽薹开花的发育和调控。在此，初步分析了连续育苗导致冬性减弱的分子机制。这对大白菜育种具有重要的指导意义。
