Plant Breeding Institute, Christian-Albrechts-University of Kiel, Olshausenstr. 40, D-24098 Kiel, Germany.
J Exp Bot. 2011 Nov;62(15):5641-58. doi: 10.1093/jxb/err249. Epub 2011 Aug 23.
Oilseed rape (Brassica napus L.) is a major oil crop which is grown worldwide. Adaptation to different environments and regional climatic conditions involves variation in the regulation of flowering time. Winter types have a strong vernalization requirement whereas semi-winter and spring types have a low vernalization requirement or flower without exposure to cold, respectively. In Arabidopsis thaliana, FRIGIDA (FRI) is a key regulator which inhibits floral transition through activation of FLOWERING LOCUS C (FLC), a central repressor of flowering which controls vernalization requirement and response. Here, four FRI homologues in B. napus were identified by BAC library screening and PCR-based cloning. While all homologues are expressed, two genes were found to be differentially expressed in aerial plant organs. One of these, BnaA.FRI.a, was mapped to a region on chromosome A03 which co-localizes with a major flowering time quantitative trait locus in multiple environments in a doubled-haploid mapping population. Association analysis of BnaA.FRI.a revealed that six SNPs, including at least one at a putative functional site, and one haplotype block, respectively, are associated with flowering time variation in 248 accessions, with flowering times differing by 13-19 d between extreme haplotypes. The results from both linkage analysis and association mapping indicate that BnaA.FRI.a is a major determinant of flowering time in oilseed rape, and suggest further that this gene also contributes to the differentiation between growth types. The putative functional polymorphisms identified here may facilitate adaptation of this crop to specific environments through marker-assisted breeding.
油菜（甘蓝型油菜）是一种重要的油料作物，在世界各地都有种植。适应不同的环境和区域气候条件涉及开花时间的调节变化。冬性品种需要较强的春化作用，而半冬性和春性品种则分别需要较低的春化作用或无需经历低温即可开花。在拟南芥中，FRIGIDA（FRI）是一个关键的调节因子，通过激活开花的关键抑制因子 FLOWERING LOCUS C（FLC）来抑制花的转变，FLC 是控制春化要求和反应的开花中央抑制剂。在这里，通过 BAC 文库筛选和基于 PCR 的克隆鉴定了油菜中的四个 FRI 同源物。虽然所有同源物都有表达，但在地上植物器官中发现有两个基因表达差异。其中之一，BnaA.FRI.a，被定位到 A03 染色体上的一个区域，该区域与一个主要的开花时间数量性状位点在多个环境中的加倍单倍体作图群体中共同定位。对 BnaA.FRI.a 的关联分析表明，6 个 SNP，包括至少一个在假定的功能位点，和一个单倍型块，分别与 248 个品种的开花时间变化相关，极端单倍型之间的开花时间差异为 13-19 天。连锁分析和关联作图的结果均表明，BnaA.FRI.a 是油菜开花时间的主要决定因素，并进一步表明该基因也有助于生长类型的分化。这里鉴定的假定功能多态性可能通过标记辅助选择育种促进该作物对特定环境的适应。
