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Article|01 May 2020|OPEN
Transcriptome analysis and metabolic profiling reveal the key role of carotenoids in the petal coloration of Liriodendron tulipifera
Zhaodong Hao1, Siqin Liu1, Lingfeng Hu1, Jisen Shi1 & Jinhui Chen1,
1Key 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

Horticulture Research 7,
Article number: 20070 (2020)
doi: 10.1038/hortres.2020.70
Views: 289

Received: 07 Nov 2019
Revised: 23 Feb 2020
Accepted: 08 Mar 2020
Published online: 01 May 2020


Liriodendron tulipifera, 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 L. tulipifera 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 L. tulipifera and Liriodendron 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 (CRTISO) and epsilon lycopene cyclase (ε-LCY), encode the core enzymes responsible for petal band-specific orange pigmentation in L. tulipifera. In particular, a putative additional ε-LCY copy specific to L. tulipifera may contribute to the distinct petal coloration pattern, compared with L. chinense. 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.