National Key Laboratory of Crop Genetic Improvement, College of Plant Science and Technology, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan, 430070, China.
College of Life Science, Institute for Conservation and Utilization of Agro-bioresources in Dabie Mountains, Xinyang Normal University, Xinyang, 464000, China.
Plant J. 2020 Nov;104(4):932-949. doi: 10.1111/tpj.14970. Epub 2020 Oct 11.
Brassica napus is currently cultivated as an important ornamental crop in China. Flower color has attracted much attention in rapeseed genetics and breeding. Here, we characterize an orange-flowered mutant of B. napus that exhibits an altered carotenoid profile in its petals. As revealed by map-based cloning, the change in color from yellow to orange is attributed to the loss of BnaC09.ZEP (zeaxanthin epoxidase) and a 1695-bp deletion in BnaA09.ZEP. HPLC analysis, genetic complementation and CRISPR/Cas9 experiments demonstrated that BnaA09.ZEP and BnaC09.ZEP have similar functions, and the abolishment of both genes led to a substantial increase in lutein content and a sharp decline in violaxanthin content in petals but not leaves. BnaA09.ZEP and BnaC09.ZEP are predominantly expressed in floral tissues, whereas their homologs, BnaA07.ZEP and BnaC07.ZEP, mainly function in leaves, indicating redundancy and tissue-specific diversification of BnaZEP function. Transcriptome analysis in petals revealed differences in the expression of carotenoid and flavonoid biosynthesis-related genes between the mutant and its complementary lines. Flavonoid profiles in the petals of complementary lines were greatly altered compared to the mutant, indicating potential cross-talk between the regulatory networks underlying the carotenoid and flavonoid pathways. Additionally, our results indicate that there is functional compensation by BnaA07.ZEP and BnaC07.ZEP in the absence of BnaA09.ZEP and BnaC09.ZEP. Cloning and characterization of BnaZEPs provide insights into the molecular mechanisms underlying flower pigmentation in B. napus and would facilitate breeding of B. napus varieties with higher ornamental value.
甘蓝型油菜目前在中国被作为一种重要的观赏作物进行栽培。花色在油菜遗传育种中受到了广泛关注。在这里，我们对甘蓝型油菜的一个橙色花瓣突变体进行了研究，该突变体在花瓣中的类胡萝卜素图谱发生了改变。通过图谱定位克隆，花色从黄色变为橙色归因于 BnaC09.ZEP（玉米黄质环氧化酶）的缺失和 BnaA09.ZEP 的 1695bp 缺失。HPLC 分析、遗传互补和 CRISPR/Cas9 实验表明，BnaA09.ZEP 和 BnaC09.ZEP 具有相似的功能，这两个基因的失活导致花瓣中叶黄素含量显著增加，而紫黄质含量急剧下降，但在叶片中没有这种变化。BnaA09.ZEP 和 BnaC09.ZEP 主要在花组织中表达，而它们的同源基因 BnaA07.ZEP 和 BnaC07.ZEP 主要在叶片中发挥作用，这表明 BnaZEP 功能具有冗余性和组织特异性多样化。花瓣转录组分析显示，突变体与其互补系之间类胡萝卜素和类黄酮生物合成相关基因的表达存在差异。互补系花瓣中的类黄酮图谱与突变体相比发生了很大改变，这表明类胡萝卜素和类黄酮途径的调控网络之间存在潜在的相互作用。此外，我们的结果表明，在缺失 BnaA09.ZEP 和 BnaC09.ZEP 的情况下，BnaA07.ZEP 和 BnaC07.ZEP 具有功能补偿。BnaZEPs 的克隆和鉴定为研究油菜花色形成的分子机制提供了线索，并将有助于培育具有更高观赏价值的油菜品种。
