title: A lignin-specific peroxidase in tobacco whose antisense suppression leads to vascular tissue modification.
abstract: A tobacco peroxidase isoenzyme (TP60) was down-regulated in tobacco using an antisense strategy, this affording transformants with lignin reductions of up to 40-50% of wild type (control) plants. Significantly, both guaiacyl and syringyl levels decreased in essentially a linear manner with the reductions in lignin amounts, as determined by both thioacidolysis and nitrobenzene oxidative analyses. These data provisionally suggest that a feedback mechanism is operative in lignifying cells, which prevents build-up of monolignols should oxidative capacity for their subsequent metabolism be reduced. Prior to this study, the only known rate-limiting processes in the monolignol/lignin pathways involved that of Phe supply and the relative activities of cinnamate-4-hydroxylase/p-coumarate-3-hydroxylase, respectively. These transformants thus provide an additional experimental means in which to further dissect and delineate the factors involved in monolignol targeting to precise regions in the cell wall, and of subsequent lignin assembly. Interestingly, the lignin down-regulated tobacco phenotypes displayed no readily observable differences in overall growth and development profiles, although the vascular apparatus was modified.
authors.affiliation: School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK.
authors.forename: Kristopher A
authors.initials: KA
authors.lastname: Blee
authors.forename: Joon W
authors.initials: JW
authors.lastname: Choi
authors.forename: Ann P
authors.initials: AP
authors.lastname: O'Connell
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schuch
authors.forename: Norman G
authors.initials: NG
authors.lastname: Lewis
authors.forename: G Paul
authors.initials: GP
authors.lastname: Bolwell
mesh_terms: D000595:Amino Acid Sequence; D017124:Conserved Sequence; D015536:Down-Regulation; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008031:Lignin / Q000096:biosynthesis* / Q000737:chemistry; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016376:Oligonucleotides, Antisense / Q000235:genetics / Q000494:pharmacology*; D010544:Peroxidases / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D018547:Plant Stems / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000201:enzymology*; D014026:Nicotiana / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*
chemical_list: D007527:Isoenzymes; D016376:Oligonucleotides, Antisense; D008031:Lignin; D006899:Mixed Function Oxygenases; D010544:Peroxidases; C042858:lignin peroxidase