title: Suppression of 4-coumarate-CoA ligase in the coniferous gymnosperm Pinus radiata.
abstract: Severe suppression of 4-coumarate-coenzyme A ligase (4CL) in the coniferous gymnosperm Pinus radiata substantially affected plant phenotype and resulted in dwarfed plants with a "bonsai tree-like" appearance. Microscopic analyses of stem sections from 2-year-old plants revealed substantial morphological changes in both wood and bark tissues. This included the formation of weakly lignified tracheids that displayed signs of collapse and the development of circumferential bands of axial parenchyma. Acetyl bromide-soluble lignin assays and proton nuclear magnetic resonance studies revealed lignin reductions of 36% to 50% in the most severely affected transgenic plants. Two-dimensional nuclear magnetic resonance and pyrolysis-gas chromatography-mass spectrometry studies indicated that lignin reductions were mainly due to depletion of guaiacyl but not p-hydroxyphenyl lignin. 4CL silencing also caused modifications in the lignin interunit linkage distribution, including elevated beta-aryl ether (beta-O-4 unit) and spirodienone (beta-1) levels, accompanied by lower phenylcoumaran (beta-5), resinol (beta-beta), and dibenzodioxocin (5-5/beta-O-4) levels. A sharp depletion in the level of saturated (dihydroconiferyl alcohol) end groups was also observed. Severe suppression of 4CL also affected carbohydrate metabolism. Most obvious was an up to approximately 2-fold increase in galactose content in wood from transgenic plants due to increased compression wood formation. The molecular, anatomical, and analytical data verified that the isolated 4CL clone is associated with lignin biosynthesis and illustrated that 4CL silencing leads to complex, often surprising, physiological and morphological changes in P. radiata.
authors.affiliation: Scion, Rotorua 3010, New Zealand. armin.wagner@scionresearch.com
authors.forename: Armin
authors.initials: A
authors.lastname: Wagner
authors.forename: Lloyd
authors.initials: L
authors.lastname: Donaldson
authors.forename: Hoon
authors.initials: H
authors.lastname: Kim
authors.forename: Lorelle
authors.initials: L
authors.lastname: Phillips
authors.forename: Heather
authors.initials: H
authors.lastname: Flint
authors.forename: Diane
authors.initials: D
authors.lastname: Steward
authors.forename: Kirk
authors.initials: K
authors.lastname: Torr
authors.forename: Gerald
authors.initials: G
authors.lastname: Koch
authors.forename: Uwe
authors.initials: U
authors.lastname: Schmitt
authors.forename: John
authors.initials: J
authors.lastname: Ralph
mesh_terms: D050260:Carbohydrate Metabolism; D003066:Coenzyme A Ligases / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D017343:Genes, Plant; D008031:Lignin / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D028223:Pinus / Q000201:enzymology* / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018547:Plant Stems / Q000033:anatomy & histology / Q000737:chemistry; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics; D014934:Wood / Q000033:anatomy & histology / Q000737:chemistry
chemical_list: D010940:Plant Proteins; D008031:Lignin; D003066:Coenzyme A Ligases; C019943:4-coumarate-CoA ligase