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Oxidosqualene cyclases involved in the biosynthesis of triterpenoids in Quercus suber cork.

ABSTRACT: Cork is a water-impermeable, suberin-based material harboring lignin, (hemi)cellulose, and extractable small molecules (primarily triterpenoids). Extractables strongly influence the properties of suberin-based materials. Though these previous findings suggest a key role for triterpenoids in cork material quality, directly testing this idea is hindered in part because it is not known which genes control cork triterpenoid biosynthesis. Here, we used gas chromatography and mass spectrometry to determine that the majority (>85%) of non-polar extractables from cork were pentacyclic triterpenoids, primarily betulinic acid, friedelin, and hydroxy-friedelin. In other plants, triterpenoids are generated by oxidosqualene cyclases (OSCs). Accordingly, we mined Quercus suber EST libraries for OSC fragments to use in a RACE PCR-based approach and cloned three full-length OSC transcripts from cork (QsOSC1-3). Heterologous expression in Saccharomyces cerevisiae revealed that QsOSC1-3 respectively encoded enzymes with lupeol synthase, mixed ?- and ?-amyrin synthase, and mixed ?-amyrin and friedelin synthase activities. These activities together account for the backbone structures of the major cork triterpenoids. Finally, we analyzed the sequences of QsOSC1-3 and other plant OSCs to identify residues associated with specific OSC activities, then combined this with analyses of Q. suber transcriptomic and genomic data to evaluate potential redundancies in cork triterpenoid biosynthesis.

SUBMITTER: Busta L

PROVIDER: S-EPMC7229149 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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Oxidosqualene cyclases involved in the biosynthesis of triterpenoids in Quercus suber cork.

Busta Lucas L Serra Olga O Kim Ok Tae OT Molinas Marisa M Peré-Fossoul Irene I Figueras Mercè M Jetter Reinhard R

Scientific reports 20200515 1

Cork is a water-impermeable, suberin-based material harboring lignin, (hemi)cellulose, and extractable small molecules (primarily triterpenoids). Extractables strongly influence the properties of suberin-based materials. Though these previous findings suggest a key role for triterpenoids in cork material quality, directly testing this idea is hindered in part because it is not known which genes control cork triterpenoid biosynthesis. Here, we used gas chromatography and mass spectrometry to dete ...[more]

PMID: 32415159

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Project description:BACKGROUND: Cork oak (Quercus suber) is one of the rare trees with the ability to produce cork, a material widely used to make wine bottle stoppers, flooring and insulation materials, among many other uses. The molecular mechanisms of cork formation are still poorly understood, in great part due to the difficulty in studying a species with a long life-cycle and for which there is scarce molecular/genomic information. Cork oak forests are of great ecological importance and represent a major economic and social resource in Southern Europe and Northern Africa. However, global warming is threatening the cork oak forests by imposing thermal, hydric and many types of novel biotic stresses. Despite the economic and social value of the Q. suber species, few genomic resources have been developed, useful for biotechnological applications and improved forest management. RESULTS: We generated in excess of 7 million sequence reads, by pyrosequencing 21 normalized cDNA libraries derived from multiple Q. suber tissues and organs, developmental stages and physiological conditions. We deployed a stringent sequence processing and assembly pipeline that resulted in the identification of ~159,000 unigenes. These were annotated according to their similarity to known plant genes, to known Interpro domains, GO classes and E.C. numbers. The phylogenetic extent of this ESTs set was investigated, and we found that cork oak revealed a significant new gene space that is not covered by other model species or EST sequencing projects. The raw data, as well as the full annotated assembly, are now available to the community in a dedicated web portal at http://www.corkoakdb.org. CONCLUSIONS: This genomic resource represents the first trancriptome study in a cork producing species. It can be explored to develop new tools and approaches to understand stress responses and developmental processes in forest trees, as well as the molecular cascades underlying cork differentiation and disease response.

Project description:Purpose:Acetylcholinesterase (AChE) inhibitors are used to treat Alzheimer's patients because they enhance cholinergic neurotransmission. It is urgent to find new and efficient inhibitors from natural sources, highly bioavailable with low or no toxicity. The plant kingdom is extremely rich in a variety of compounds that are potent AChE inhibitors: flavonoids and other phenolic compounds have been recognized as promising Alzheimer's treatment agents. In this study, in vitro acetylcholinesterase inhibition, antioxidant activities, and total flavonoid and phenolic contents of ethanol-water extracts from Quercus suber cork and corkback were evaluated. Methods:The acetylcholinesterase activity was determined by a colorimetric assay based on Ellman's methodology. The Folin-Ciocalteu colorimetric method was used for total phenolic content determination and the aluminium chloride method for the determination of total flavonoid content. Antioxidant activity assays were performed using the DPPH and FRAP assays. Results:The acetylcholinesterase inhibitory activity from Q. suber cork and corkback ethanol-water extracts was as follows: 62% inhibition with corkback extracts over 0.5?mg/mL and around 49% inhibition in cork extracts over 1.0?mg/mL extracts' concentration. Regarding the DPPH radical scavenging activity, the concentrations of cork and corkback ethanol-water extracts required for 50% DPPH inhibition (IC50) were 3.2??g/mL and 4.0-5.2??g/mL. Corkback extracts are less effective than Trolox standard (3.2??g/mL) but cork extracts showed the same free radical scavenging activity compared to Trolox. Cork and corkback extracts have antioxidant power of 750.9-775.4?mg TEAC/g extract and 1051.2-2052.4?mg TEAC/g extract, respectively, which are significantly higher than the ones obtained with Trolox: 19.6-21.0?mg TEAC/g extract (cork assays) and 57.4-66.3?mg TEAC/g extract (corkback assays). The amounts of total phenolic (TPC) and flavonoid (TFC) compounds were 8.7-32.3?mg GAE/g and 4.8-10.7?mg CE/g dry mass for cork and 5.4-5.7?mg GAE/g and 42.5?mg CE/g dry mass for corkback extracts, respectively, using catechin (CE) and GAE (gallic acid) as standards. Conclusion:These findings demonstrate the remarkable potential of these extracts as valuable source of antioxidants with interesting acetylcholinesterase inhibitory activity.

Dataset Information

Oxidosqualene cyclases involved in the biosynthesis of triterpenoids in Quercus suber cork.

Publications

Oxidosqualene cyclases involved in the biosynthesis of triterpenoids in Quercus suber cork.

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