title: Acylphloroglucinol Biosynthesis in Strawberry Fruit.
abstract: Phenolics have health-promoting properties and are a major group of metabolites in fruit crops. Through reverse genetic analysis of the functions of four ripening-related genes in the octoploid strawberry (Fragaria × ananassa), we discovered four acylphloroglucinol (APG)-glucosides as native Fragaria spp. fruit metabolites whose levels were differently regulated in the transgenic fruits. The biosynthesis of the APG aglycones was investigated by examination of the enzymatic properties of three recombinant Fragaria vesca chalcone synthase (FvCHS) proteins. CHS is involved in anthocyanin biosynthesis during ripening. The F. vesca enzymes readily catalyzed the condensation of two intermediates in branched-chain amino acid metabolism, isovaleryl-Coenzyme A (CoA) and isobutyryl-CoA, with three molecules of malonyl-CoA to form phlorisovalerophenone and phlorisobutyrophenone, respectively, and formed naringenin chalcone when 4-coumaroyl-CoA was used as starter molecule. Isovaleryl-CoA was the preferred starter substrate of FvCHS2-1. Suppression of CHS activity in both transient and stable CHS-silenced fruit resulted in a substantial decrease of APG glucosides and anthocyanins and enhanced levels of volatiles derived from branched-chain amino acids. The proposed APG pathway was confirmed by feeding isotopically labeled amino acids. Thus, Fragaria spp. plants have the capacity to synthesize pharmaceutically important APGs using dual functional CHS/(phloriso)valerophenone synthases that are expressed during fruit ripening. Duplication and adaptive evolution of CHS is the most probable scenario and might be generally applicable to other plants. The results highlight that important promiscuous gene function may be missed when annotation relies solely on in silico analysis.
authors.affiliation: Biotechnology of Natural Products, Technische Universität München, 85354 Freising, Germany (C.S., L.R., T.H., F.-C.H., W.S.); andUnited States Department of Agriculture/Agricultural Research Service Genetic Improvement of Fruits and Vegetables Laboratory, Beltsville 20705, Maryland (J.S.).
authors.forename: Chuankui
authors.initials: C
authors.lastname: Song
authors.affiliation: Biotechnology of Natural Products, Technische Universität München, 85354 Freising, Germany (C.S., L.R., T.H., F.-C.H., W.S.); andUnited States Department of Agriculture/Agricultural Research Service Genetic Improvement of Fruits and Vegetables Laboratory, Beltsville 20705, Maryland (J.S.).
authors.forename: Ludwig
authors.initials: L
authors.lastname: Ring
authors.affiliation: Biotechnology of Natural Products, Technische Universität München, 85354 Freising, Germany (C.S., L.R., T.H., F.-C.H., W.S.); andUnited States Department of Agriculture/Agricultural Research Service Genetic Improvement of Fruits and Vegetables Laboratory, Beltsville 20705, Maryland (J.S.).
authors.forename: Thomas
authors.initials: T
authors.lastname: Hoffmann
authors.affiliation: Biotechnology of Natural Products, Technische Universität München, 85354 Freising, Germany (C.S., L.R., T.H., F.-C.H., W.S.); andUnited States Department of Agriculture/Agricultural Research Service Genetic Improvement of Fruits and Vegetables Laboratory, Beltsville 20705, Maryland (J.S.).
authors.forename: Fong-Chin
authors.initials: FC
authors.lastname: Huang
authors.affiliation: Biotechnology of Natural Products, Technische Universität München, 85354 Freising, Germany (C.S., L.R., T.H., F.-C.H., W.S.); andUnited States Department of Agriculture/Agricultural Research Service Genetic Improvement of Fruits and Vegetables Laboratory, Beltsville 20705, Maryland (J.S.).
authors.forename: Janet
authors.identifier: http://orcid.org/0000-0001-6609-7034
authors.initials: J
authors.lastname: Slovin
authors.affiliation: Biotechnology of Natural Products, Technische Universität München, 85354 Freising, Germany (C.S., L.R., T.H., F.-C.H., W.S.); andUnited States Department of Agriculture/Agricultural Research Service Genetic Improvement of Fruits and Vegetables Laboratory, Beltsville 20705, Maryland (J.S.) wilfried.schwab@tum.de.
authors.forename: Wilfried
authors.identifier: http://orcid.org/0000-0002-9753-3967
authors.initials: W
authors.lastname: Schwab
mesh_terms: D031985:Fragaria / Q000378:metabolism*; D005638:Fruit / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D020868:Gene Silencing; D005960:Glucosides / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism; D015394:Molecular Structure; D010696:Phloroglucinol / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D010860:Pigments, Biological; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D059467:Transcriptome
chemical_list: D005960:Glucosides; D010860:Pigments, Biological; D010940:Plant Proteins; D010696:Phloroglucinol