Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark.
Genome Research and Molecular Biomedicine, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
BMC Genomics. 2018 Nov 8;19(1):811. doi: 10.1186/s12864-018-5135-6.
Anthocyanins are water-soluble colored flavonoids present in multiple organs of various plant species including flowers, fruits, leaves, stems and roots. DNA-binding R2R3-MYB transcription factors, basic helix-loop-helix (bHLH) transcription factors, and WD40 repeat proteins are known to form MYB-bHLH-WD repeat (MBW) complexes, which activates the transcription of structural genes in the anthocyanin pathway. Although black cultivars of carrots (Daucus carota L.) can accumulate large quantities of anthocyanin in their storage roots, the regulatory genes responsible for their biosynthesis are not well characterized. The current study aimed to analyze global transcription profiles based on RNA sequencing (RNA-Seq), and mine MYB, bHLH and WD40 genes that may function as positive or negative regulators in the carrot anthocyanin biosynthesis pathways.
RNA was isolated from differently colored calli, as well as tissue samples from taproots of various black carrot cultivars across the course of development, and gene expression levels of colored and non-colored tissue and callus samples were compared. The expression of 32 MYB, bHLH and WD40 genes were significantly correlated with anthocyanin content in black carrot taproot. Of those, 11 genes were consistently up- or downregulated in a purple color-specific manner across various calli and cultivar comparisons. The expression of 10 out of these 11 genes was validated using real-time quantitative reverse transcriptase polymerase chain reaction (qRT-PCR).
The results of this study provide insights into regulatory genes that may be responsible for carrot anthocyanin biosynthesis, and suggest that future focus on them may help improve our overall understanding of the anthocyanin synthesis pathway.
花色苷是一种水溶性的有色类黄酮，存在于多种植物物种的多个器官中，包括花、果实、叶、茎和根。现已知道 DNA 结合 R2R3-MYB 转录因子、碱性螺旋-环-螺旋（bHLH）转录因子和 WD40 重复蛋白形成 MYB-bHLH-WD 重复（MBW）复合物，该复合物激活花色苷途径中结构基因的转录。尽管胡萝卜（Daucus carota L.）的黑色品种可以在其贮藏根中积累大量的花色苷，但负责其生物合成的调控基因尚未得到很好的描述。本研究旨在基于 RNA 测序（RNA-Seq）分析全局转录谱，并挖掘可能作为胡萝卜花色苷生物合成途径中正向或负向调控因子的 MYB、bHLH 和 WD40 基因。
从不同颜色的愈伤组织以及各种黑色胡萝卜品种的主根发育过程中的组织样品中分离出 RNA，并比较有色和无色组织和愈伤组织样品的基因表达水平。32 个 MYB、bHLH 和 WD40 基因的表达与黑色胡萝卜主根中的花色苷含量显著相关。在各种愈伤组织和品种比较中，有 11 个基因以特定于紫色的方式一致地上调或下调。使用实时定量逆转录聚合酶链反应（qRT-PCR）验证了其中 10 个基因的表达。
本研究的结果提供了可能负责胡萝卜花色苷生物合成的调控基因的见解，并表明未来对这些基因的关注可能有助于我们全面了解花色苷合成途径。
