title: Multi-site modulation of flux during monolignol formation in loblolly pine (Pinus taeda).
abstract: Loblolly pine (Pinus taeda L.) cell suspension cultures secrete monolignols when placed in 8% sucrose/20 mM KI solution, and these were used to identify phenylpropanoid pathway flux-modulating steps. When cells were provided with increasing amounts of either phenylalanine (Phe) or cinnamic acid, cellular concentrations of immediate downstream products (cinnamic and p-coumaric acids, respectively) increased, whereas caffeic and ferulic acid pool sizes were essentially unaffected. Increasing Phe concentrations resulted in increased amounts of p-coumaryl alcohol relative to coniferyl alcohol. However, exogenously supplied cinnamic, p-coumaric, caffeic, and ferulic acids resulted only in increases in their intercellular concentrations, but not that of downstream cinnamyl aldehydes and monolignols. Supplying p-coumaryl and coniferyl aldehydes up to 40, 000-320,000-fold above the detection limits resulted in rapid, quantitative conversion into the monolignols. Only at nonphysiological concentrations was transient accumulation of intracellular aldehydes observed. These results indicate that cinnamic and p-coumaric acid hydroxylations assume important regulatory positions in phenylpropanoid metabolism, whereas cinnamyl aldehyde reduction does not serve as a control point.
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, 99164-6340, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Anterola
authors.forename: H
authors.initials: H
authors.lastname: van Rensburg
authors.forename: P S
authors.initials: PS
authors.lastname: van Heerden
authors.forename: L B
authors.initials: LB
authors.lastname: Davin
authors.forename: N G
authors.initials: NG
authors.lastname: Lewis
mesh_terms: D000447:Aldehydes / Q000008:administration & dosage; D002109:Caffeic Acids / Q000378:metabolism; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D002934:Cinnamates / Q000008:administration & dosage / Q000378:metabolism; D003373:Coumaric Acids / Q000378:metabolism; D005960:Glucosides / Q000378:metabolism; D007700:Kinetics; D008031:Lignin / Q000096:biosynthesis*; D010649:Phenylalanine / Q000008:administration & dosage / Q000378:metabolism; D041603:Pinus taeda
chemical_list: D000447:Aldehydes; D002109:Caffeic Acids; D002934:Cinnamates; D003373:Coumaric Acids; D005960:Glucosides; C029010:cinnamic acid; D010649:Phenylalanine; D008031:Lignin; C004999:ferulic acid; C040048:caffeic acid