title: Hinokinin biosynthesis in Linum corymbulosum Reichenb.
abstract: Due to their peculiar stereochemistry and numerous biological activities, lignans are of widespread interest. As only a few biosynthetic steps have been clarified to date, we aimed to further resolve the molecular basis of lignan biosynthesis. To this end, we first established that the biologically active lignan (-)-hinokinin could be isolated from in vitro cultures of Linum corymbulosum. Two hypothetical pathways were outlined for the biosynthesis of (-)-hinokinin. In both pathways, (+)-pinoresinol serves as the primary substrate. In the first pathway, pinoresinol is reduced via lariciresinol to secoisolariciresinol by a pinoresinol-lariciresinol reductase, and methylenedioxy bridges are formed later. In the second pathway, pinoresinol itself is the substrate for formation of the methylenedioxy bridges, resulting in consecutive production of piperitol and sesamin. To determine which of the proposed hypothetical pathways acts in vivo, we first isolated several cDNAs encoding one pinoresinol-lariciresinol reductase (PLR-Lc1), two phenylcoumaran benzylic ether reductases (PCBER-Lc1 and PCBER-Lc2), and two PCBER-like proteins from a cDNA library of L. corymbulosum. PLR-Lc1 was found to be enantiospecific for the conversion of (+)-pinoresinol to (-)-secoisolariciresinol, which can be further converted to give (-)-hinokinin. Hairy root lines with significantly reduced expression levels of the plr-Lc1 gene were established using RNAi technology. Hinokinin accumulation was reduced to non-detectable levels in these lines. Our results strongly indicate that PLR-Lc1 participates in (-)-hinokinin biosynthesis in L. corymbulosum by the first of the two hypothetical pathways via (-)-secoisolariciresinol.
authors.affiliation: Institut für Entwicklungs- und Molekularbiologie der Pflanzen, Heinrich-Heine-Universität Düsseldorf, Universitätsstrasse 1, D-40225 Düsseldorf, Germany.
authors.forename: Urün
authors.initials: U
authors.lastname: Bayindir
authors.forename: August Wilhelm
authors.initials: AW
authors.lastname: Alfermann
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Fuss
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000096:biosynthesis; D000595:Amino Acid Sequence; D052117:Benzodioxoles; D002072:Butylene Glycols / Q000378:metabolism; D002478:Cells, Cultured; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004149:Dioxoles; D019597:Flax / Q000201:enzymology* / Q000235:genetics; D005663:Furans / Q000378:metabolism; D015870:Gene Expression; D015723:Gene Library; D017343:Genes, Plant; D017705:Lignans / Q000096:biosynthesis* / Q000378:metabolism; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000378:metabolism; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D052117:Benzodioxoles; D002072:Butylene Glycols; D018076:DNA, Complementary; D004149:Dioxoles; D005663:Furans; D017705:Lignans; D010940:Plant Proteins; D018749:RNA, Plant; C475934:hinokinin; C060282:lariciresinol; D010088:Oxidoreductases; C084968:lariciresinol reductase; C084969:pinoresinol reductase; C118150:phenylcoumaran benzylic ether reductase; C060283:secoisolariciresinol; D015107:4-Butyrolactone; C103298:pinoresinol