Wageningen UR Plant Breeding, PO Box 386, AJ 6700 Wageningen, The Netherlands.
J Exp Bot. 2013 Nov;64(14):4503-16. doi: 10.1093/jxb/ert264. Epub 2013 Sep 27.
The role of many genes and interactions among genes involved in flowering time have been studied extensively in Arabidopsis, and the purpose of this study was to investigate how effectively results obtained with the model species Arabidopsis can be applied to the Brassicacea with often larger and more complex genomes. Brassica rapa represents a very close relative, with its triplicated genome, with subgenomes having evolved by genome fractionation. The question of whether this genome fractionation is a random process, or whether specific genes are preferentially retained, such as flowering time (Ft) genes that play a role in the extreme morphological variation within the B. rapa species (displayed by the diverse morphotypes), is addressed. Data are presented showing that indeed Ft genes are preferentially retained, so the next intriguing question is whether these different orthologues of Arabidopsis Ft genes play similar roles compared with Arabidopsis, and what is the role of these different orthologues in B. rapa. Using a genetical-genomics approach, co-location of flowering quantitative trait loci (QTLs) and expression QTLs (eQTLs) resulted in identification of candidate genes for flowering QTLs and visualization of co-expression networks of Ft genes and flowering time. A major flowering QTL on A02 at the BrFLC2 locus co-localized with cis eQTLs for BrFLC2, BrSSR1, and BrTCP11, and trans eQTLs for the photoperiod gene BrCO and two paralogues of the floral integrator genes BrSOC1 and BrFT. It is concluded that the BrFLC2 Ft gene is a major regulator of flowering time in the studied doubled haploid population.
许多参与开花时间的基因及其相互作用在拟南芥中得到了广泛研究，本研究的目的是探讨在 Brassica rapa 中，模型物种拟南芥的研究结果的有效性， Brassica rapa 基因组通常更大且更复杂。Brassica rapa 代表一个非常近的亲缘物种，其基因组经过三倍化，亚基因组通过基因组片段化进化而来。问题是这种基因组片段化是随机过程，还是特定基因被优先保留，例如在 Brassica rapa 物种内（通过不同的形态类型显示）极端形态变异中起作用的开花时间（Ft）基因。本文提供的数据表明，实际上 Ft 基因被优先保留，因此下一个有趣的问题是，拟南芥 Ft 基因的这些不同同源基因是否与拟南芥具有相似的作用，以及这些不同的同源基因在 Brassica rapa 中的作用是什么。使用遗传基因组学方法，开花数量性状位点（QTL）和表达 QTL（eQTL）的共定位导致了候选基因的鉴定，以及对 Ft 基因和开花时间的共表达网络的可视化。在 BrFLC2 基因座的 A02 上的一个主要开花 QTL 与 BrFLC2、BrSSR1 和 BrTCP11 的顺式 eQTL 以及光周期基因 BrCO 和 floral 整合基因 BrSOC1 和 BrFT 的两个同源基因的反式 eQTL 共定位。研究结果表明，在研究的双单倍体群体中，BrFLC2 Ft 基因是开花时间的主要调控基因。
