Yuan Yu-Xiang, Wu Jian, Sun Ri-Fei, Zhang Xiao-Wei, Xu Dong-Hui, Bonnema Guusje, Wang Xiao-Wu
Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
J Exp Bot. 2009;60(4):1299-308. doi: 10.1093/jxb/erp010. Epub 2009 Feb 3.
FLOWERING LOCUS C (FLC), encoding a MADS-domain transcription factor in Arabidopsis, is a repressor of flowering involved in the vernalization pathway. This provides a good reference for Brassica species. Genomes of Brassica species contain several FLC homologues and several of these colocalize with flowering-time QTL. Here the analysis of sequence variation of BrFLC1 in Brassica rapa and its association with the flowering-time phenotype is reported. The analysis revealed that a G-->A polymorphism at the 5' splice site in intron 6 of BrFLC1 is associated with flowering phenotype. Three BrFLC1 alleles with alternative splicing patterns, including two with different parts of intron 6 retained and one with the entire exon 6 excluded from the transcript, were identified in addition to alleles with normal splicing. It was inferred that aberrant splicing of the pre-mRNA leads to loss-of-function of BrFLC1. A CAPS marker was developed for this locus to distinguish Pi6+1(G) and Pi6+1(A). The polymorphism detected with this marker was significantly associated with flowering time in a collection of 121 B. rapa accessions and in a segregating Chinese cabbage doubled-haploid population. These findings suggest that a naturally occurring splicing mutation in the BrFLC1 gene contributes greatly to flowering-time variation in B. rapa.
开花位点C（FLC）在拟南芥中编码一种MADS结构域转录因子，是参与春化途径的开花抑制因子。这为芸苔属物种提供了很好的参考。芸苔属物种的基因组包含几个FLC同源物，其中一些与开花时间QTL共定位。本文报道了白菜型油菜中BrFLC1的序列变异分析及其与开花时间表型的关联。分析表明，BrFLC1第6内含子5'剪接位点的G→A多态性与开花表型相关。除了正常剪接的等位基因外，还鉴定出了三种具有可变剪接模式的BrFLC1等位基因，其中两种保留了第6内含子的不同部分，一种转录本中排除了整个第6外显子。据推测，前体mRNA的异常剪接导致BrFLC1功能丧失。针对该位点开发了一个CAPS标记，以区分Pi6+1(G)和Pi6+1(A)。在121份白菜型油菜种质资源和一个分离的大白菜双单倍体群体中，用该标记检测到的多态性与开花时间显著相关。这些发现表明，BrFLC1基因中自然发生的剪接突变对白菜型油菜的开花时间变异有很大贡献。
