期刊
PLANT JOURNAL
卷 93, 期 1, 页码 92-106出版社
WILEY
DOI: 10.1111/tpj.13760
关键词
C12; 8-fused STLs; cytochrome P450 (CYP); germacrene A acid C8-hydroxylase; Inula hupehensis; inunolide; sesquiterpene lactones (STLs)
资金
- National Natural Science Foundation of China [31370339, 81230090, 81520108030]
- Ministry of Science and Technology of China [2011YQ120035]
- Natural Sciences and Engineering Research Council of Canada (NSERC)
- Next-Generation Bio-Green 21 Program (SSAC) from Rural Development Administration, Republic of Korea [PJ01105501]
- Basic Science Research Programme through the National Research Foundation of Korea (NRF) - Ministry of Education [2017R1A6A3A03003409]
- National Research Foundation of Korea [2017R1A6A3A03003409] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
Sesquiterpene lactones (STLs) are C15 terpenoid natural products with alpha-methylene gamma-lactone moiety. A large proportion of STLs in Asteraceae species is derived from the central precursor germacrene A acid (GAA). Formation of the lactone rings depends on the regio-(C6 or C8) and stereoselective (alpha- or beta-)hydroxylations of GAA, producing STLs with four distinct stereo-configurations (12,6 alpha-, 12,6-, 12, 8 alpha-, and 12,8 beta-olide derivatives of GAA) in nature. Curiously, two configurations of STLs (C12,8 alpha and C12,8 beta) are simultaneously present in the Chinese medicinal plant, Inula hupehensis. However, how these related yet distinct STL stereo-isomers are co-synthesized in I. hupehensis remains unknown. Here, we describe the functional identification of the I. hupehensis cytochrome P450 (CYP71BL6) that can catalyze the hydroxylation of GAA in either 8 alpha-or 8 beta-configuration, resulting in the synthesis of both 8 alpha- and 8 beta-hydroxyl GAAs. Of these two products, only 8 alpha-hydroxyl GAA spontaneously lactonizes to the C12,8 alpha-STL while the 8 beta-hydroxyl GAA remains stable without lactonization. Chemical structures of the C12,8 alpha-STL, named inunolide, and 8 beta-hydroxyl GAA were fully elucidated by nuclear magnetic resonance analysis and mass spectrometry. The CYP71BL6 displays 63-66% amino acid identity to the previously reported CYP71BL1/2 catalyzing GAA 6aor 8 beta-hydroxylation, indicating CYP71BL6 shares the same evolutionary lineage with other stereoselective cytochrome P450s, but catalyzes hydroxylation in a non-stereoselective manner. We observed that the CYP71BL6 transcript abundance correlates closely to the accumulation of C12,8-STLs in I. hupehensis. The identification of CYP71BL6 provides an insight into the biosynthesis of STLs in Asteraceae.
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