Liu Chunqing, Yao Xueqin, Li Guangqing, Huang Lei, Xie Zhujie
Shanghai Academy of Agricultural Sciences, Institute of Horticulture, Shanghai, China.
School of Ecological Technology and Engineering, Shanghai Institute of Technology, Shanghai, China.
PeerJ. 2020 May 5;8:e8870. doi: 10.7717/peerj.8870. eCollection 2020.
Purple Broccoli ( L. var ) attracts growing attention as a functional food. Its purple coloration is due to high anthocyanin amounts. Light represents a critical parameter affecting anthocyanins biosynthesis. In this study, 'Purple Broccoli', a light-responding pigmentation cultivar, was assessed for exploring the mechanism underlying light-induced anthocyanin biosynthesis by RNA-Seq. Cyanidin, delphinidin and malvidin derivatives were detected in broccoli head samples. Shading assays and RNA-seq analysis identified the flower head as more critical organ compared with leaves. Anthocyanin levels were assessed at 0, 7 and 11 days, respectively, with further valuation by RNA-seq under head-shading and light conditions. RNA sequences were de novo assembled into 50,329 unigenes, of which 38,701 were annotated against four public protein databases. Cluster analysis demonstrated that anthocyanin/phenylpropanoid biosynthesis, photosynthesis, and flavonoid biosynthesis in cluster 8 were the main metabolic pathways regulated by light and had showed associations with flower head growth. A total of 2,400 unigenes showed differential expression between the light and head-shading groups in cluster 8, including 650 co-expressed, 373 specifically expressed under shading conditions and 1,377 specifically expressed under normal light. Digital gene expression (DGE) analysis demonstrated that light perception and the signal transducers and may control anthocyanin accumulation. Following shading, 15 structural genes involved in anthocyanin biosynthesis were downregulated, including , , 4CL, , , and . Moreover, six BoMYB genes (, , , , and ) and three BobHLH genes (, and ) were critical transcription factors controlling anthocyanin accumulation under light conditions. Based on these data, a light-associated anthocyanin biosynthesis pathway in Broccoli was proposed. This information could help improve broccoli properties, providing novel insights into the molecular mechanisms underpinning light-associated anthocyanin production in purple vegetables.
紫花椰菜（L. var）作为一种功能性食品，越来越受到关注。其紫色是由于花青素含量高。光代表影响花青素生物合成的关键参数。在本研究中，通过RNA测序评估了对光有响应的色素沉着品种“紫花椰菜”，以探索光诱导花青素生物合成的潜在机制。在西兰花头样品中检测到矢车菊素、飞燕草素和锦葵素衍生物。遮光试验和RNA测序分析表明，与叶片相比，花球是更关键的器官。分别在第0、7和11天评估花青素水平，并在花球遮光和光照条件下通过RNA测序进行进一步评估。RNA序列被从头组装成50329个单基因，其中38701个与四个公共蛋白质数据库进行了注释比对。聚类分析表明，第8组中的花青素/苯丙烷生物合成、光合作用和类黄酮生物合成是受光调节的主要代谢途径，并且与花球生长有关。共有2400个单基因在第8组的光照和花球遮光组之间表现出差异表达，包括650个共表达的、373个在遮光条件下特异性表达的和1377个在正常光照下特异性表达的。数字基因表达（DGE）分析表明，光感知以及信号转导因子和可能控制花青素积累。遮光后，15个参与花青素生物合成的结构基因被下调，包括、、4CL、、、和。此外，6个BoMYB基因（、、、、和）和3个BobHLH基因（、和）是在光照条件下控制花青素积累的关键转录因子。基于这些数据，提出了西兰花中与光相关的花青素生物合成途径。这些信息有助于改善西兰花的特性，为紫色蔬菜中与光相关的花青素产生的分子机制提供新的见解。
