title: 4-Coumarate:CoA ligase family members from elicitor-treated Sorbus aucuparia cell cultures.
abstract: Sorbus aucuparia cell cultures accumulate biphenyl and dibenzofuran phytoalexins in response to elicitor treatment. These polyketide derivatives arise from the starter substrate benzoyl-CoA, the biosynthesis of which is largely unresolved. Two CoA ligases involved are cinnamate:CoA ligase and benzoate:CoA ligase, which were assumed to be related in S. aucuparia to the ubiquitous 4-coumarate:CoA ligase (4CL). cDNAs encoding three distinct 4CLs from elicitor-treated S. aucuparia cell cultures were isolated using RT-PCR and RACE techniques and functionally expressed in Escherichia coli as His(6)-tagged proteins (Sa4CL2 and Sa4CL3) or GST-fusion protein (Sa4CL1). All three isoenzymes preferred 4-coumaric acid over cinnamic acid in spectrophotometric assays and failed to utilize benzoic acid in radioisotopic assays. After elicitor treatment of S. aucuparia cell cultures, the transcript levels of all three Sa4CLs increased but were significantly lower than the maximum expression rates of the phenylalanine ammonia-lyase (PAL) and biphenyl synthase 1 (BIS1) genes. The substrate specificities and the expression profiles indicate that the three 4CL isoenzymes are not involved in benzoyl-CoA biosynthesis in S. aucuparia cell cultures. Sa4CL3 and PAL transcripts also accumulated in response to light treatment. Phylogenetically, Sa4CL1 and Sa4CL2 belong to the class I cluster and Sa4CL3 groups in the class II cluster. Sa4CL3 contains a 49-amino acid N-terminal extension, which includes a chloroplast sorting signal.
authors.affiliation: Institut für Pharmazeutische Biologie, Technische Universität Braunschweig, Mendelssohnstraße 1, D-38106 Braunschweig, Germany.
authors.forename: Mariam M
authors.initials: MM
authors.lastname: Gaid
authors.forename: Helge
authors.initials: H
authors.lastname: Scharnhop
authors.forename: Hussein
authors.initials: H
authors.lastname: Ramadan
authors.forename: Till
authors.initials: T
authors.lastname: Beuerle
authors.forename: Ludger
authors.initials: L
authors.lastname: Beerhues
mesh_terms: D000595:Amino Acid Sequence; D019817:Benzoic Acid / Q000737:chemistry; D002109:Caffeic Acids / Q000737:chemistry; D002478:Cells, Cultured; D048271:Chitosan / Q000737:chemistry; D002934:Cinnamates / Q000737:chemistry; D003001:Cloning, Molecular; D003066:Coenzyme A Ligases / Q000737:chemistry* / Q000235:genetics; D003373:Coumaric Acids / Q000737:chemistry; D020869:Gene Expression Profiling; D007527:Isoenzymes / Q000737:chemistry; D008027:Light; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry; D010650:Phenylalanine Ammonia-Lyase; D010802:Phylogeny; D011422:Propionates; D031994:Sorbus / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D013379:Substrate Specificity
chemical_list: D002109:Caffeic Acids; D002934:Cinnamates; D003373:Coumaric Acids; D007527:Isoenzymes; D009097:Multienzyme Complexes; D011422:Propionates; C482658:biphenyl synthase, Sorbus aucuparia; C029010:cinnamic acid; D019817:Benzoic Acid; D048271:Chitosan; C004999:ferulic acid; D010650:Phenylalanine Ammonia-Lyase; D003066:Coenzyme A Ligases; C019943:4-coumarate-CoA ligase; C055455:benzoate coenzyme A ligase; C495469:p-coumaric acid; C040048:caffeic acid