title: Antisense down-regulation of 4CL expression alters lignification, tree growth, and saccharification potential of field-grown poplar.
abstract: Transgenic down-regulation of the Pt4CL1 gene family encoding 4-coumarate:coenzyme A ligase (4CL) has been reported as a means for reducing lignin content in cell walls and increasing overall growth rates, thereby improving feedstock quality for paper and bioethanol production. Using hybrid poplar (Populus tremula × Populus alba), we applied this strategy and examined field-grown transformants for both effects on wood biochemistry and tree productivity. The reductions in lignin contents obtained correlated well with 4CL RNA expression, with a sharp decrease in lignin amount being observed for RNA expression below approximately 50% of the nontransgenic control. Relatively small lignin reductions of approximately 10% were associated with reduced productivity, decreased wood syringyl/guaiacyl lignin monomer ratios, and a small increase in the level of incorporation of H-monomers (p-hydroxyphenyl) into cell walls. Transgenic events with less than approximately 50% 4CL RNA expression were characterized by patches of reddish-brown discolored wood that had approximately twice the extractive content of controls (largely complex polyphenolics). There was no evidence that substantially reduced lignin contents increased growth rates or saccharification potential. Our results suggest that the capacity for lignin reduction is limited; below a threshold, large changes in wood chemistry and plant metabolism were observed that adversely affected productivity and potential ethanol yield. They also underline the importance of field studies to obtain physiologically meaningful results and to support technology development with transgenic trees.
authors: Department of Wood Science and Engineering, Oregon State University, Corvallis, Oregon 97331, USA.
authors: Steven L
authors: SL
authors: Voelker
authors: Barbara
authors: B
authors: Lachenbruch
authors: Frederick C
authors: FC
authors: Meinzer
authors: Michael
authors: M
authors: Jourdes
authors: Chanyoung
authors: C
authors: Ki
authors: Ann M
authors: AM
authors: Patten
authors: Laurence B
authors: LB
authors: Davin
authors: Norman G
authors: NG
authors: Lewis
authors: Gerald A
authors: GA
authors: Tuskan
authors: Lee
authors: L
authors: Gunter
authors: Stephen R
authors: SR
authors: Decker
authors: Michael J
authors: MJ
authors: Selig
authors: Robert
authors: R
authors: Sykes
authors: Michael E
authors: ME
authors: Himmel
authors: Peter
authors: P
authors: Kitin
authors: Olga
authors: O
authors: Shevchenko
authors: Steven H
authors: SH
authors: Strauss
mesh_terms: D018533:Biomass; D003066:Coenzyme A Ligases / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D008031:Lignin / Q000737:chemistry*; D008969:Molecular Sequence Data; D010636:Phenols / Q000032:analysis; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D032107:Populus / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D016372:RNA, Antisense / Q000235:genetics*; D014197:Trees / Q000254:growth & development*; D014934:Wood / Q000737:chemistry
chemical_list: D010636:Phenols; D016372:RNA, Antisense; D008031:Lignin; D003066:Coenzyme A Ligases