Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Zhongguancun Southern Street 12, Beijing, 100081, China.
Theor Appl Genet. 2018 Oct;131(10):2107-2116. doi: 10.1007/s00122-018-3139-x. Epub 2018 Jul 14.
A splicing site mutation in BrFLC5, a non-syntenic paralogue of FLOWERING LOCUS C, was demonstrated to be related to flowering time variation in Brassica rapa. Flowering time regulation in Brassica rapa is more complex than in Arabidopsis, as there are multiple paralogues of flowering time genes in B. rapa. Brassica rapa contains four FLOWERING LOCUS C (FLC) genes, three of which are syntenic orthologues of AtFLC, while BrFLC5 is not. BrFLC1, BrFLC2, and BrFLC3 have been reported to be involved in flowering time regulation. However, BrFLC5 has thus far been deemed a pseudogene. We detected two alternative splicing patterns of BrFLC5 resulting from a nucleotide mutation (G/A) at the first nucleotide of intron 3 (named as Pi3+1(G/A)). Genotyping of BrFLC5Pi3 + 1(G/A) for 301 B. rapa accessions showed that this single nucleotide polymorphism was significantly related to flowering time variation (p < 0.001). In the collection, the frequency of the functional G allele (35.2%) was much lower than that of the nonfunctional A allele (59.1%); however, the frequency of the G allele was very high among the turnips (83.6%). An F2 population segregating at this locus was developed to analyze the genetic effect of BrFLC5. The result showed that the G allele individuals began to bolt two days later than the A allele individuals, indicating that BrFLC5 is a weak regulator of flowering time. BrFLC5 was expressed at the lowest level among the three analyzed BrFLCs. The late allele (G allele) was dominant to the early allele (A allele) at the BrFLC5 locus, which was in contrast to that of BrFLC1 and BrFLC2. This characteristic suggests that BrFLC5 would be more efficient for breeding premature bolting resistance in B. rapa.
甘蓝型油菜 BrFLC5 剪接位点突变与开花时间的变异有关，BrFLC5 是 FLOWERING LOCUS C 的非同源基因。甘蓝型油菜的开花时间调控比拟南芥更为复杂，因为在甘蓝型油菜中有多个开花时间基因的同源基因。甘蓝型油菜含有四个 FLOWERING LOCUS C（FLC）基因，其中三个是 AtFLC 的同源基因，而 BrFLC5 则不是。BrFLC1、BrFLC2 和 BrFLC3 已被报道参与开花时间的调控。然而，BrFLC5 迄今为止被认为是一个假基因。我们检测到 BrFLC5 的两种剪接模式，这是由于第 3 内含子的第一个核苷酸发生核苷酸突变（G/A）（命名为 Pi3+1(G/A)）所致。对 301 个甘蓝型油菜品系进行 BrFLC5Pi3+1(G/A)的基因分型表明，这个单核苷酸多态性与开花时间的变异显著相关（p<0.001）。在该群体中，功能 G 等位基因（35.2%）的频率明显低于非功能 A 等位基因（59.1%）；然而，在萝卜中 G 等位基因的频率非常高（83.6%）。开发了一个分离该基因座的 F2 群体，以分析 BrFLC5 的遗传效应。结果表明，G 等位基因个体比 A 等位基因个体晚开花两天，表明 BrFLC5 是一个弱的开花时间调控因子。在分析的三个 BrFLC 中，BrFLC5 的表达水平最低。该基因座的晚花等位基因（G 等位基因）对早花等位基因（A 等位基因）具有显性，这与 BrFLC1 和 BrFLC2 相反。这一特征表明，BrFLC5 更有利于培育甘蓝型油菜早熟抗抽薹性。
