背景:明亮的花颜色有助于植物吸引昆虫完成授粉并提供独特的观赏价值。在一些药用植物中,不同的花颜色变化通常意味着活性成分的差异。与黄芩花(SB)常见的蓝紫色相比,在山东省真正的产区,在相同的生长条件下筛选出玫瑰红(SR)和白色(SW)花的天然变体,中国。然而,黄芩花色变异的机理尚不清楚。在本研究中,我们进行了整合的转录组和代谢组分析,以揭示三种黄芩花的代谢差异和调节机制。
结果:结果表明鉴定出9种花色苷。其中,仅在SB中检测到4种基于delphinidin的花色苷,4基于花青素的花青素(不含花青素-3-O-葡萄糖苷)主要在SR中积累,没有花色苷,但黄烷酮含量很高,柚皮苷,在SW中检测到。基因表达谱表明,类黄酮和花色苷生物合成途径中的关键结构基因在不同颜色的花中差异表达。与SB相比,F3\'5\'H的表达下调,ANS,SR中的3GT基因可能会影响花色苷的组成。特别是SR中F3\'5\'H中缺失7个核苷酸的InDel位点(AATAGAG)可能是玫瑰红花中缺乏基于飞燕素的花色苷的决定因素。在SW,DFR和两个F3H基因的较低表达水平可能会减少花青素的积累。值得注意的是,SW中DFR剪接位点中G>A突变的SNP位点可能会阻断黄酮类化合物的花色苷生物合成,从而导致白花。此外,几个关键的转录因子,包括MYB,bHLH,NAC,还鉴定了与结构基因表达和花色苷含量高度相关的基因。
结论:这些结果为揭示黄芩花色变异的分子调控机制提供了线索,并促进了对花色苷生物合成和调控的新认识。
BACKGROUND: Bright flower colour assists plants attract insects to complete pollination and provides distinct ornamental values. In some medicinal plants, diverse flower colour variations usually imply differences in active ingredients. Compared to the common bluish purple of Scutellaria baicalensis flower (SB), the natural variants present rose red (SR) and white (SW) flowers were screened out under the same growing conditions in the genuine producing area Shandong Province, China. However, the mechanism of flower colour variation in S. baicalensis was remain unclear. In the present study, we conducted integrated transcriptome and metabolome analyses to uncover the metabolic difference and regulation mechanism in three S. baicalensis flowers.
RESULTS: The results showed that 9 anthocyanins were identified. Among which, 4 delphinidin-based anthocyanins were only detected in SB, 4 cyanidin-based anthocyanins (without cyanidin-3-O-glucoside) mainly accumulated in SR, and no anthocyanin but high level of flavanone, naringenin, was detected in SW. The gene expression profile indicated that the key structural genes in the flavonoid and anthocyanin biosynthesis pathway differentially expressed in flowers with different colours. Compared to SB, the down-regulated expression of F3\'5\'H, ANS, and 3GT gene in SR might influence the anthocyanin composition. Especially the InDel site with deletion of 7 nucleotides (AATAGAG) in F3\'5\'H in SR might be the determinant for lack of delphinidin-based anthocyanins in rose red flowers. In SW, the lower expression levels of DFR and two F3H genes might reduce the anthocyanin accumulation. Notably the SNP site of G > A mutation in the splicing site of DFR in SW might block anthocyanin biosynthesis from flavanones and thus cause white flowers. In addition, several key transcription factors, including MYB, bHLH, and NAC, which highly correlated with structural gene expression and anthocyanin contents were also identified.
CONCLUSIONS: These results provide clues to uncover the molecular regulatory mechanism of flower colour variation in S. baicalensis and promote novel insights into understanding the anthocyanin biosynthesis and regulation.