title: Laccase is necessary and nonredundant with peroxidase for lignin polymerization during vascular development in Arabidopsis.
abstract: The evolution of lignin biosynthesis was critical in the transition of plants from an aquatic to an upright terrestrial lifestyle. Lignin is assembled by oxidative polymerization of two major monomers, coniferyl alcohol and sinapyl alcohol. Although two recently discovered laccases, LAC4 and LAC17, have been shown to play a role in lignin polymerization in Arabidopsis thaliana, disruption of both genes only leads to a relatively small change in lignin content and only under continuous illumination. Simultaneous disruption of LAC11 along with LAC4 and LAC17 causes severe plant growth arrest, narrower root diameter, indehiscent anthers, and vascular development arrest with lack of lignification. Genome-wide transcript analysis revealed that all the putative lignin peroxidase genes are expressed at normal levels or even higher in the laccase triple mutant, suggesting that lignin laccase activity is necessary and nonredundant with peroxidase activity for monolignol polymerization during plant vascular development. Interestingly, even though lignin deposition in roots is almost completely abolished in the lac11 lac4 lac17 triple mutant, the Casparian strip, which is lignified through the activity of peroxidase, is still functional. Phylogenetic analysis revealed that lignin laccase genes have no orthologs in lower plant species, suggesting that the monolignol laccase genes diverged after the evolution of seed plants.
authors.affiliation: Plant Biology Division, Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401.
authors.forename: Qiao
authors.initials: Q
authors.lastname: Zhao
authors.forename: Jin
authors.initials: J
authors.lastname: Nakashima
authors.forename: Fang
authors.initials: F
authors.lastname: Chen
authors.forename: Yanbin
authors.initials: Y
authors.lastname: Yin
authors.forename: Chunxiang
authors.initials: C
authors.lastname: Fu
authors.forename: Jianfei
authors.initials: J
authors.lastname: Yun
authors.forename: Hui
authors.initials: H
authors.lastname: Shao
authors.forename: Xiaoqiang
authors.initials: X
authors.lastname: Wang
authors.forename: Zeng-Yu
authors.initials: ZY
authors.lastname: Wang
authors.forename: Richard A
authors.initials: RA
authors.lastname: Dixon
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D042845:Laccase / Q000235:genetics / Q000378:metabolism*; D008031:Lignin / Q000096:biosynthesis*; D010544:Peroxidases / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D058526:Plant Vascular Bundle / Q000254:growth & development; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: D029681:Arabidopsis Proteins; D014157:Transcription Factors; D008031:Lignin; D042845:Laccase; D010544:Peroxidases; C042858:lignin peroxidase