title: Involvement of extracellular dilignols in lignification during tracheary element differentiation of isolated Zinnia mesophyll cells.
abstract: During differentiation of isolated Zinnia mesophyll cells into tracheary elements (TEs), lignification on TEs progresses by supply of monolignols not only from TEs themselves but also from surrounding xylem parenchyma-like cells through the culture medium. However, how lignin polymerizes from the secreted monolignols has not been resolved. In this study, we analyzed phenol compounds in culture medium with reversed-phase HPLC, gas chromatography-mass spectrometry and nuclear magnetic resonance spectrometry, and found 12 phenolic compounds including coniferyl alcohol and four dilignols, i.e. erythro-guaiacylglycerol-beta-coniferyl ether, threo-guaiacylglycerol-beta-coniferyl ether, dehydrodiconiferyl alcohol and pinoresinol, in the medium in which TEs were developing. Coniferyl alcohol applied to TE-inductive cultures during TE formation rapidly disappeared from the medium, and caused a sudden increase in dilignols. Addition of the dilignols promoted lignification of TEs in which monolignol biosynthesis was blocked by an inhibitor of phenylalanine anmmonia-lyase (PAL), L-alpha-aminooxy-beta-phenylpropionic acid (AOPP). These results suggested that dilignols can act as intermediates of lignin polymerization.
authors.affiliation: Department of Biology and Earth Sciences, Faculty of Science, Ehime University, Matsuyama, 790-8577 Japan.
authors.forename: Naohito
authors.initials: N
authors.lastname: Tokunaga
authors.forename: Norikazu
authors.initials: N
authors.lastname: Sakakibara
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Umezawa
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Ito
authors.forename: Hiroo
authors.initials: H
authors.lastname: Fukuda
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Sato
mesh_terms: D019659:Asteraceae / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D002454:Cell Differentiation; D002851:Chromatography, High Pressure Liquid; D008401:Gas Chromatography-Mass Spectrometry; D008031:Lignin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008954:Models, Biological; D015394:Molecular Structure; D010636:Phenols / Q000737:chemistry / Q000378:metabolism; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D010636:Phenols; C019145:alpha-aminooxy-beta-phenylpropionic acid; D010649:Phenylalanine; D008031:Lignin