title: Biosynthesis of the major tetrahydroxystilbenes in spruce, astringin and isorhapontin, proceeds via resveratrol and is enhanced by fungal infection.
abstract: Stilbenes are dibenzyl polyphenolic compounds produced in several unrelated plant families that appear to protect against various biotic and abiotic stresses. Stilbene biosynthesis has been well described in economically important plants, such as grape (Vitis vinifera), peanut (Arachis hypogaea), and pine (Pinus species). However, very little is known about the biosynthesis and ecological role of stilbenes in spruce (Picea), an important gymnosperm tree genus in temperate and boreal forests. To investigate the biosynthesis of stilbenes in spruce, we identified two similar stilbene synthase (STS) genes in Norway spruce (Picea abies), PaSTS1 and PaSTS2, which had orthologs with high sequence identity in sitka (Picea sitchensis) and white (Picea glauca) spruce. Despite the conservation of STS sequences in these three spruce species, they differed substantially from angiosperm STSs. Several types of in vitro and in vivo assays revealed that the P. abies STSs catalyze the condensation of p-coumaroyl-coenzyme A and three molecules of malonyl-coenzyme A to yield the trihydroxystilbene resveratrol but do not directly form the dominant spruce stilbenes, which are tetrahydroxylated. However, in transgenic Norway spruce overexpressing PaSTS1, significantly higher amounts of the tetrahydroxystilbene glycosides, astringin and isorhapontin, were produced. This result suggests that the first step of stilbene biosynthesis in spruce is the formation of resveratrol, which is further modified by hydroxylation, O-methylation, and O-glucosylation to yield astringin and isorhapontin. Inoculating spruce with fungal mycelium increased STS transcript abundance and tetrahydroxystilbene glycoside production. Extracts from STS-overexpressing lines significantly inhibited fungal growth in vitro compared with extracts from control lines, suggesting that spruce stilbenes have a role in antifungal defense.
authors.affiliation: Department of Biochemistry, Max Planck Institute for Chemical Ecology, 07745 Jena, Germany.
authors.forename: Almuth
authors.initials: A
authors.lastname: Hammerbacher
authors.forename: Steven G
authors.initials: SG
authors.lastname: Ralph
authors.forename: Joerg
authors.initials: J
authors.lastname: Bohlmann
authors.forename: Trevor M
authors.initials: TM
authors.lastname: Fenning
authors.forename: Jonathan
authors.initials: J
authors.lastname: Gershenzon
authors.forename: Axel
authors.initials: A
authors.lastname: Schmidt
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism; D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001203:Ascomycota / Q000472:pathogenicity; D003066:Coenzyme A Ligases / Q000235:genetics / Q000378:metabolism; D017124:Conserved Sequence; D004926:Escherichia coli / Q000235:genetics; D005960:Glucosides / Q000378:metabolism*; D006031:Glycosylation; D054884:Host-Pathogen Interactions; D006900:Hydroxylation; D008316:Malonyl Coenzyme A / Q000378:metabolism; D008745:Methylation; D008969:Molecular Sequence Data; D010802:Phylogeny; D028222:Picea / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology*; D010935:Plant Diseases / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D000077185:Resveratrol; D013267:Stilbenes / Q000378:metabolism*
chemical_list: D000214:Acyl Coenzyme A; D005960:Glucosides; D010940:Plant Proteins; D013267:Stilbenes; C121481:astringin; C571114:isorhapontin; C058644:4-coumaroyl-coenzyme A; D008316:Malonyl Coenzyme A; D000217:Acyltransferases; C022674:stilbene synthase; D003066:Coenzyme A Ligases; C019943:4-coumarate-CoA ligase; D000077185:Resveratrol