Functional characterization of an oxidosqualene cyclase (PdFRS) encoding a monofunctional friedelin synthase in Populus davidiana

• Published in: Planta Vol. 249; no. 1; pp. 95 - 111
• Main Authors: Han, Jung Yeon, Ahn, Chang-Ho, Adhikari, Prakash Babu, Kondeti, Subramanyam, Choi, Yong Eui
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Science + Business Media 01.01.2019; Springer Berlin Heidelberg; Springer Nature B.V
• Subjects: Agriculture; Amino acid sequence; Amino acids; Biomedical and Life Sciences; Biosynthesis; Chemical compounds; Ecology; Forestry; Gene expression; Genetic transformation; Intramolecular Transferases - genetics; Intramolecular Transferases - metabolism; Life Sciences; Methyl jasmonate; Organic chemistry; ORIGINAL ARTICLE; Plant Proteins - genetics; Plant Proteins - metabolism; Plant Sciences; Populus - genetics; Populus - metabolism; Populus davidiana; Proteins; Saponins; Sterols; Terpenes and Isoprenoids; Triterpenes; Triterpenes - metabolism; Yeast; Yeasts; Friedelin synthase; Triterpene synthase; Oxidosqualene cyclase; Populus davidiana
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-018-2985-8

Triterpenes are one of the largest classes of plant chemical compounds composed of three terpene units, which form the basic skeleton of all sterols and saponins. Friedelin (friedelan-3-one), a pentacyclic triterpene, occurs in many plant families and is particularly present in rich amounts in cork tissues from trees. The biosynthesis of friedelin occurs through the oxidosqualene cyclase (OSC) enzyme that generates friedelin from 2,3-oxidosqualene after the maximum rearrangement of a triterpene skeleton. Populus davidiana is called Korean aspen and grows in northern East Asia. From 57,322 unique sequences generated from the P. davidiana transcriptome database, one complete coding sequence (PdFRS) was obtained from a contig, which showed 74% identity to Betula platyphylla β-amyrin synthase and 73% identity with friedelin synthase from Maytenus ilicifolia. The open reading frame (ORF) region of the PdFRS sequence was 2280 bp long and composed a 759 amino acid protein with a predicted molecular mass of 87.81 kDa. qPCR analysis revealed that methyl jasmonate treatments strongly upregulated PdFRS gene expression and resulted in enhanced friedelin accumulation in leaves. Heterologous expression of the PdFRS gene in yeast resulted in the production of friedelin triterpene as a single product, which was confirmed by comparison with the mass fragmentation pattern from an authentic friedelin standard by GC/MS analysis. Transgenic P. davidiana overexpressing the PdFRS gene was constructed via Agrobacterium-mediated transformation. Overexpression of PdFRS in transgenic P. davidiana lines resulted in enhanced friedelin production.