Publications

• Identification, functional characterization and developmental regulation of sesquiterpene synthases from sunflower capitate glandular trichomes.

  Goepfert J.C., Macnevin G., Ro D.-K., Spring O.

  <h4>Background</h4>Sesquiterpene lactones are characteristic metabolites of Asteraceae (or Compositae) which often display potent bioactivities and are sequestered in specialized organs such as laticifers, resin ducts, and trichomes. For characterization of sunflower sesquiterpene synthases we emp ... >> More

  <h4>Background</h4>Sesquiterpene lactones are characteristic metabolites of Asteraceae (or Compositae) which often display potent bioactivities and are sequestered in specialized organs such as laticifers, resin ducts, and trichomes. For characterization of sunflower sesquiterpene synthases we employed a simple method to isolate pure trichomes from anther appendages which facilitated the identification of these genes and investigation of their enzymatic functions and expression patterns during trichome development.<h4>Results</h4>Glandular trichomes of sunflower (Helianthus annuus L.) were isolated, and their RNA was extracted to investigate the initial steps of sesquiterpene lactone biosynthesis. Reverse transcription-PCR experiments led to the identification of three sesquiterpene synthases. By combination of in vitro and in vivo characterization of sesquiterpene synthase gene products in Escherichia coli and Saccharomyces cerevisiae, respectively, two enzymes were identified as germacrene A synthases, the key enzymes of sesquiterpene lactone biosynthesis. Due to the very low in vitro activity, the third enzyme was expressed in vivo in yeast as a thioredoxin-fusion protein for functional characterization. In in vivo assays, it was identified as a multiproduct enzyme with the volatile sesquiterpene hydrocarbon delta-cadinene as one of the two main products with alpha-muuorlene, beta-caryophyllene, alpha-humulene and alpha-copaene as minor products. The second main compound remained unidentified. For expression studies, glandular trichomes from the anther appendages of sunflower florets were isolated in particular developmental stages from the pre-to the post-secretory phase. All three sesquiterpene synthases were solely upregulated during the biosynthetically active stages of the trichomes. Expression in different aerial plant parts coincided with occurrence and maturity of trichomes. Young roots with root hairs showed expression of the sesquiterpene synthase genes as well.<h4>Conclusion</h4>This study functionally identified sesquiterpene synthase genes predominantly expressed in sunflower trichomes. Evidence for the transcriptional regulation of sesquiterpene synthase genes in trichome cells suggest a potential use for these specialized cells for the identification of further genes involved in the biosynthesis, transport, and regulation of sesquiterpene lactones. << Less

  BMC Plant Biol. 9:86-86(2009) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.

• Diversity of sesquiterpene synthases in the basidiomycete Coprinus cinereus.

  Agger S., Lopez-Gallego F., Schmidt-Dannert C.

  Fungi are a rich source of bioactive secondary metabolites, and mushroom-forming fungi (Agaricomycetes) are especially known for the synthesis of numerous bioactive and often cytotoxic sesquiterpenoid secondary metabolites. Compared with the large number of sesquiterpene synthases identified in pl ... >> More

  Fungi are a rich source of bioactive secondary metabolites, and mushroom-forming fungi (Agaricomycetes) are especially known for the synthesis of numerous bioactive and often cytotoxic sesquiterpenoid secondary metabolites. Compared with the large number of sesquiterpene synthases identified in plants, less than a handful of unique sesquiterpene synthases have been described from fungi. Here we describe the functional characterization of six sesquiterpene synthases (Cop1 to Cop6) and two terpene-oxidizing cytochrome P450 monooxygenases (Cox1 and Cox2) from Coprinus cinereus. The genes were cloned and, except for cop5, functionally expressed in Escherichia coli and/or Saccharomyces cerevisiae. Cop1 and Cop2 each synthesize germacrene A as the major product. Cop3 was identified as an alpha-muurolene synthase, an enzyme that has not been described previously, while Cop4 synthesizes delta-cadinene as its major product. Cop6 was originally annotated as a trichodiene synthase homologue but instead was found to catalyse the highly specific synthesis of alpha-cuprenene. Coexpression of cop6 and the two monooxygenase genes next to it yields oxygenated alpha-cuprenene derivatives, including cuparophenol, suggesting that these genes encode the enzymes for the biosynthesis of antimicrobial quinone sesquiterpenoids (known as lagopodins) that were previously isolated from C. cinereus and other Coprinus species. << Less

  Mol. Microbiol. 72:1181-1195(2009) [PubMed] [EuropePMC]

  This publication is cited by 4 other entries.

• Selectivity of fungal sesquiterpene synthases: role of the active site's H-1 alpha loop in catalysis.

  Lopez-Gallego F., Wawrzyn G.T., Schmidt-Dannert C.

  Sesquiterpene synthases are responsible for the cyclization of farnesyl pyrophosphate into a myriad of structurally diverse compounds with various biological activities. We examine here the role of the conserved active site H-α1 loop in catalysis in three previously characterized fungal sesquiterp ... >> More

  Sesquiterpene synthases are responsible for the cyclization of farnesyl pyrophosphate into a myriad of structurally diverse compounds with various biological activities. We examine here the role of the conserved active site H-α1 loop in catalysis in three previously characterized fungal sesquiterpene synthases. The H-α1 loops of Cop3, Cop4, and Cop6 from Coprinus cinereus were altered by site-directed mutagenesis and the resultant product profiles were analyzed by gas chromatography-mass spectrometry and compared to the wild-type enzymes. In addition, we examine the effect of swapping the H-α1 loop from the promiscuous enzyme Cop4 with the more selective Cop6 and the effect of acidic or basic conditions on loop mutations in Cop4. Directed mutations of the H-α1 loop had a marked effect on the product profile of Cop3 and Cop4, while little to no change was shown in Cop6. Swapping of the Cop4 and Cop6 loops with one another was again shown to influence the product profile of Cop4, while the product profile of Cop6 remained identical to the wild-type enzyme. The loop mutations in Cop4 also implicate specific residues responsible for the pH sensitivity of the enzyme. These results affirm the role of the H-α1 loop in catalysis and provide a potential target to increase the product diversity of terpene synthases. << Less

  Appl. Environ. Microbiol. 76:7723-7733(2010) [PubMed] [EuropePMC]

  This publication is cited by 4 other entries.