Recently, The Plant Journal officially published a research paper entitled "Gene silencing of BnaA09.ZEP and BnaC09.ZEP confers orange color in Brassica napus flowers" by Fu Tingdong's group of our school. The results provide a theoretical basis for revealing the molecular mechanism of rape flower color formation, and bioengineering technology to improve rape flower color and create colorful rape germplasm resources (Nanhu News Network (Correspondent Ye Shenhua).
This study showed that the simultaneous mutation of two homologous genes BnaA09.ZEP and BnaC09.ZEP, encoding zeaxanthin cyclase (ZEP) in Brassica napus could affect the biosynthesis of carotenoids in petals, resulting in the transformation of yellow flowers into orange flowers. The results provide a theoretical basis for the formation of color in rape germplasm. In recent years, with the vigorous development of rape flower tourism, the genetic improvement of rape ornamental traits has gradually attracted the attention of researchers. Although it is known that the yellow flower phenotype of Brassica napus is mainly determined by carotenoids, few studies have carried out cloning and functional studies on the flower color genes except the white flower gene reported by the team in 2015.
In this study, the key flower color genes BnaA09.ZEP and BnaC09.ZEP were isolated and identified by map-based cloning, and their functions were studied. There are four homologous copies of ZEP gene in Brassica napus. BnaA09.ZEP and BnaC09.ZEP are mainly expressed in flowers, while BnaA07.ZEP and BnaC07.ZEP are dominant in leaves. Transgene complementation and CRISPR experiments showed that the simultaneous silencing of BnaA09.ZEP and BnaC09.ZEP resulted in flower color mutation from yellow flower to orange flower. The introduction of a single BnaA09.ZEP or BnaC09.ZEP could restore the flower color to yellow, suggesting that Zep gene has functional redundancy and organ-specific functional differentiation in Brassica napus. The results of HPLC, transcription group and metabolic group showed that the silencing of BnaA07.ZEP and BnaC07.ZEP may cause response regulation of carotenoid synthesis pathways. The key genes of α - carotene and β - carotene branch have significant expression changes, which makes the biosynthesis of purple yellow matter greatly reduced, while lutein accumulated a lot and the color of flower was orange; on the other hand, the two genes were significantly reduced The mutation of the gene also leads to the significant expression changes of key transcription factors and structural genes in the synthesis pathway of flavonoids, and there are also significant differences in flavonoids in petals of different colors, suggesting the coordinated regulation of carotenoids and flavonoids synthesis pathway.
Doctoral student Liu Yingjun from the College of Plant Science and Technology of Huazhong Agricultural University is the first author of the paper, and Associate Professor Wen Jing is the corresponding author of the paper. The research was funded by the National Key Research and Development Program, China Scholarship Council, Modern Agricultural Industrial Technology System, and other projects.
Paper link: https:https://onlinelibrary.wiley.com/doi/10.1111/tpj.14970
Translated by: Zhao Zihan
Revised by: Aamir Sohail