Hao Zhaodong, Liu Siqin, Hu Lingfeng, Shi Jisen, Chen Jinhui
Key Laboratory of Forest Genetics and Biotechnology of Ministry of Education, Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, Jiangsu China.
Hortic Res. 2020 May 1;7:70. doi: 10.1038/s41438-020-0287-3. eCollection 2020.
, also known as tuliptree, is a popular ornamental horticultural plant with extraordinary tulip-shaped flowers characterized by an orange band near their base. The mechanisms underlying petal band-specific pigmentation during flower development are unclear. Here, we combined nontargeted and targeted metabolomics and transcriptomics to identify a pathway cascade leading to carotenoid biosynthesis that is specifically activated in the petal band. The comparative analysis of carotenoid metabolites between and hybrids indicates that γ-carotene, a rare carotene in plants, is the most likely orange pigment responsible for the coloration of the petal band. Phenotypic and transcriptomic analyses of developing petals reveal that the band area is first predefined by the loss of green color. Later, the band is maintained by locally activating and repressing carotenoid and chlorophyll biosynthesis genes, respectively. Two rate-limiting genes of carotene biosynthesis, carotenoid isomerase () and epsilon lycopene cyclase (), encode the core enzymes responsible for petal band-specific orange pigmentation in . In particular, a putative additional copy specific to may contribute to the distinct petal coloration pattern, compared with . Taken together, our work provides a first glimpse of the metabolome and transcriptome dynamics in tuliptree flower coloration and provides a valuable resource for flower breeding or metabolic engineering as well as for understanding flower evolution in an early woody angiosperm.
（又称鹅掌楸）是一种受欢迎的观赏园艺植物，其花朵呈独特的郁金香形状，基部附近有橙色条纹。花朵发育过程中花瓣条纹特异性色素沉着的潜在机制尚不清楚。在这里，我们结合非靶向和靶向代谢组学以及转录组学，以确定一条导致类胡萝卜素生物合成的途径级联，该途径在花瓣条纹中被特异性激活。对鹅掌楸及其杂种之间类胡萝卜素代谢物的比较分析表明，γ-胡萝卜素（一种植物中罕见的类胡萝卜素）是最有可能导致花瓣条纹着色的橙色色素。对发育中的花瓣进行表型和转录组分析表明，条纹区域首先由绿色的丧失预先确定。后来，条纹通过分别局部激活和抑制类胡萝卜素和叶绿素生物合成基因来维持。类胡萝卜素生物合成的两个限速基因，类胡萝卜素异构酶（）和ε-番茄红素环化酶（），编码负责鹅掌楸花瓣条纹特异性橙色色素沉着的核心酶。特别是，与鹅掌楸相比，一个假定的特定于鹅掌楸的额外基因拷贝可能有助于形成独特的花瓣着色模式。综上所述，我们的工作首次揭示了鹅掌楸花色中的代谢组和转录组动态，为花卉育种或代谢工程以及理解早期木本被子植物的花进化提供了宝贵资源。
