Laccase down-regulation causes alterations in phenolic metabolism and cell wall structure in poplar.
Laccases are encoded by multigene families in plants. Previously, we reported the cloning and characterization of five divergent laccase genes from poplar (Populus trichocarpa) xylem. To investigate the role of individual laccase genes in plant development, and more particularly in lignification, three independent populations of antisense poplar plants, lac3AS, lac90AS, and lac110AS with significantly reduced levels of laccase expression were generated. A repression of laccase gene expression had no effect on overall growth and development. Moreover, neither lignin content nor composition was significantly altered as a result of laccase suppression. However, one of the transgenic populations, lac3AS, exhibited a 2- to 3-fold increase in total soluble phenolic content. As indicated by toluidine blue staining, these phenolics preferentially accumulate in xylem ray parenchyma cells. In addition, light and electron microscopic observations of lac3AS stems indicated that lac3 gene suppression led to a dramatic alteration of xylem fiber cell walls. Individual fiber cells were severely deformed, exhibiting modifications in fluorescence emission at the primary wall/middle lamella region and frequent sites of cell wall detachment. Although a direct correlation between laccase gene expression and lignification could not be assigned, we show that the gene product of lac3 is essential for normal cell wall structure and integrity in xylem fibers. lac3AS plants provide a unique opportunity to explore laccase function in plants.
Ranocha
Philippe
P
Unité Mixte de Recherche, Centre National de la Recherche Scientifique-Université Paul Sabatier 5546 Signaux et Messages Cellulaires chez les Végétaux, Pôle de Biotechnologie Végétale, 24, Chemin de Borde Rouge, 31326 Castanet Tolosan, France.
Chabannes
Matthieu
M
Chamayou
Simon
S
Danoun
Saïda
S
Jauneau
Alain
A
Boudet
Alain-M
AM
Goffner
Deborah
D
D001592:Benzyl Alcohols / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism* / Q000648:ultrastructure; D016373:DNA, Antisense / Q000235:genetics; D015536:Down-Regulation; D018506:Gene Expression Regulation, Plant; D005960:Glucosides / Q000378:metabolism; D042845:Laccase; D008027:Light; D008031:Lignin / Q000737:chemistry / Q000378:metabolism*; D008854:Microscopy, Electron; D015394:Molecular Structure; D005810:Multigene Family; D010088:Oxidoreductases / Q000235:genetics*; D010636:Phenols / Q000737:chemistry / Q000378:metabolism*; D030821:Plants, Genetically Modified; D012333:RNA, Messenger / Q000032:analysis; D031308:Salicaceae / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D013057:Spectrum Analysis
D001592:Benzyl Alcohols; D016373:DNA, Antisense; D005960:Glucosides; D010636:Phenols; D012333:RNA, Messenger; C095421:tremulacin; C005696:salicin; D008031:Lignin; D010088:Oxidoreductases; D042845:Laccase; C113068:salicortin