Discovery of germacrene A synthases in Barnadesia spinosa: The first committed step in sesquiterpene lactone biosynthesis in the basal member of the Asteraceae

Nguyen, Trinh-Don, Faraldos, Juan A., Vardakou, Maria, Salmon, Melissa, O'Maille, Paul E. and Ro, Dae-Kyun (2016) Discovery of germacrene A synthases in Barnadesia spinosa: The first committed step in sesquiterpene lactone biosynthesis in the basal member of the Asteraceae. Biochemical and Biophysical Research Communications, 479 (4). 622–627. ISSN 0006-291X

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Abstract

The Andes-endemic Barnadesioideae lineage is the oldest surviving and phylogenetically basal subfamily of the Asteraceae (Compositae), a prolific group of flowering plants with world-wide distribution (∼24,000 species) marked by a rich diversity of sesquiterpene lactones (STLs). Intriguingly, there is no evidence that members of the Barnadesioideae produce STLs, specialized metabolites thought to have contributed to the adaptive success of the Asteraceae family outside South America. The biosynthesis of STLs requires the intimate expression and functional integration of germacrene A synthase (GAS) and germacrene A oxidase (GAO) to sequentially cyclize and oxidize farnesyl diphosphate into the advanced intermediate germacrene A acid leading to diverse STLs. Our previous discovery of GAO activity conserved across all major subfamilies of Asteraceae, including the phylogenetically basal lineage of Barnadesioideae, prompted further investigation of the presence of the gateway GAS in Barnadesioideae. Herein we isolated two terpene synthases (BsGAS1/BsGAS2) from the basal Barnadesia spinosa (Barnadesioideae) that displayed robust GAS activity when reconstituted in yeast and characterized in vitro. Despite the apparent lack of STLs in the Barnadesioideae, this work unambiguously confirms the presence of GAS in the basal genera of the Asteraceae. Phylogenetic analysis reveals that the two BsGASs fall into two distinct clades of the Asteraceae's GASs, and BsGAS1 clade is only retained in the evolutionary closer Cichorioideae subfamily, implicating BsGAS2 is likely the ancestral base of most GASs found in the lineages outside the Barnadesioideae. Taken together, these results show the enzymatic capacities of GAS and GAO emerged prior to the subsequent radiation of STL-producing Asteraceae subfamilies.

Item Type: Article
Additional Information: Date of Acceptance: 30/09/2016
Uncontrolled Keywords: germacrene a synthase,terpene synthase,sesquiterpene lactone,asteraceae,barnadesia spinosa
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Pure Connector
Date Deposited: 22 Oct 2016 21:33
Last Modified: 14 Nov 2020 00:53
URI: https://ueaeprints.uea.ac.uk/id/eprint/61001
DOI: 10.1016/j.bbrc.2016.09.165

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