Xu Suxia, Huang Qingyun, Lin Chunsong, Lin Lixian, Zhou Qun, Lin Fucong, He Enming
Key Laboratory of Plant Physiology and Biochemistry, Fujian Institute of Subtropical Botany, 780-800 Jiahe Road, Xiamen 361006, PR China.
Xiamen Botanical Garden, 25 Huyuan Road, Xiamen 361003, PR China.
Funct Plant Biol. 2016 Mar;43(3):278-286. doi: 10.1071/FP15246.
The occurrence of betalains and anthocyanins is mutually exclusive, which is a curious phenomenon in the plant kingdom, and the biochemical mechanisms for this restriction are unknown. In the present study, we performed transcriptome analysis of two betalain-producing species, red Bougainvillea glabra Choisy. 'Sanderiana' (R) and white B. glabra 'Alba' (W) by transcriptome sequencing. In total, we obtained 69692 (Red) and 60727 (White) genes with an average length of 665 and 728bp respectively. Out of 3106 significantly differentially-expressed genes (71%), 1003 were R-specific (32%), and 1605 were W-specific (52%). To validate betalain-/anthocyanidin-biosynthesis genes detected (cytochrome P 450 76AD1 (CYP76AD1), dihydroxy-phenylalanine (DOPA)-4,5-dioxygenase (DODA), cyclo DOPA-5-O-glycosyltransferase (cyclo-DOPA-5-GT) dihydroflavonol 4-reductase (DFR), leucoanthocyanidin dioxygenase (LDOX)), real-time PCR was performed in leaves and three development stages of flowers in four Bougainvilleas, red R, white W, orange Bougainvillea×buttiana 'Salmoea' (O) and purple B. glabra 'Formosa' (P). Contents of betalains were also measured. The results showed that betalains accumulation was consistent with the expression level of DODA in O. A correlation between expression of CYP76AD1 and cyclo-DOPA-5GT and betalains was not discovered. This suggests that production of betacyanins was under the regulation of more complex factors. Both DFR and LDOX responsible for anthocyanidin production were first validated in floral organs and leaves in betalain-producing plants by real-time PCR. These findings suggest a fully functioning anthocyanin pathway, at least, to the stage of LDOX in bougainvilleas.
甜菜色素和花青素的出现是相互排斥的，这在植物界是一个奇特的现象，而这种限制的生化机制尚不清楚。在本研究中，我们通过转录组测序对两种产生甜菜色素的物种进行了转录组分析，即红色叶子花（Bougainvillea glabra Choisy.）‘桑德瑞那’（R）和白色叶子花‘阿尔巴’（W）。我们总共获得了69692个（红色）和60727个（白色）基因，平均长度分别为665和728bp。在3106个显著差异表达基因中（71%），1003个是R特有的（32%），1605个是W特有的（52%）。为了验证检测到的甜菜色素/花青素生物合成基因（细胞色素P450 76AD1（CYP76AD1）、二羟基苯丙氨酸（DOPA）-4,5-双加氧酶（DODA）、环多巴-5-O-糖基转移酶（环多巴-5-GT）、二氢黄酮醇4-还原酶（DFR）、无色花青素双加氧酶（LDOX）），我们在四种叶子花（红色R、白色W、橙色杂交叶子花（Bougainvillea×buttiana）‘萨尔莫埃亚’（O）和紫色叶子花‘福尔摩沙’（P））的叶片和花的三个发育阶段进行了实时定量PCR。我们还测量了甜菜色素的含量。结果表明，甜菜色素的积累与橙色叶子花中DODA的表达水平一致。未发现CYP76AD1和环多巴-5GT的表达与甜菜色素之间存在相关性。这表明甜菜青素的产生受更复杂因素的调控。通过实时定量PCR首次在产生甜菜色素的植物的花器官和叶片中验证了负责花青素产生的DFR和LDOX。这些发现表明，至少在叶子花中，花青素途径至少在LDOX阶段是完全起作用的。
