Down-regulation of caffeic acid o-methyltransferase in maize revisited using a transgenic approach.
Transgenic maize (Zea mays) plants were generated with a construct harboring a maize caffeic acid O-methyltransferase (COMT) cDNA in the antisense (AS) orientation under the control of the maize Adh1 (alcohol dehydrogenase) promoter. Adh1-driven beta-glucuronidase expression was localized in vascular tissues and lignifying sclerenchyma, indicating its suitability in transgenic experiments aimed at modifying lignin content and composition. One line of AS plants, COMT-AS, displayed a significant reduction in COMT activity (15%-30% residual activity) and barely detectable amounts of COMT protein as determined by western-blot analysis. In this line, transgenes were shown to be stably integrated in the genome and transmitted to the progeny. Biochemical analysis of COMT-AS showed: (a) a strong decrease in Klason lignin content at the flowering stage, (b) a decrease in syringyl units, (c) a lower p-coumaric acid content, and (d) the occurrence of unusual 5-OH guaiacyl units. These results are reminiscent of some characteristics already observed for the maize bm3 (brown-midrib3) mutant, as well as for COMT down-regulated dicots. However, as compared with bm3, COMT down-regulation in the COMT-AS line is less severe in that it is restricted to sclerenchyma cells. To our knowledge, this is the first time that an AS strategy has been applied to modify lignin biosynthesis in a grass species.
Piquemal
Joel
J
Signaux et Messages Cellulaires chez les Végétaux, Unité Mixte de Recherche, Centre National de la Recherche Scientifique-Université Paul Sabatier, Pôle de Biotechnologie Végétale, Castanet Tolosan, France.
Chamayou
Simon
S
Nadaud
Isabelle
I
Beckert
Michel
M
Barrière
Yves
Y
Mila
Isabelle
I
Lapierre
Catherine
C
Rigau
Joan
J
Puigdomenech
Pere
P
Jauneau
Alain
A
Digonnet
Catherine
C
Boudet
Alain-Michel
AM
Goffner
Deborah
D
Pichon
Magalie
M
D003373:Coumaric Acids / Q000378:metabolism; D015536:Down-Regulation; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D006651:Histocytochemistry; D008031:Lignin / Q000378:metabolism; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D010641:Phenotype; D018547:Plant Stems / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011422:Propionates; D013379:Substrate Specificity; D003313:Zea mays / Q000235:genetics* / Q000378:metabolism
D003373:Coumaric Acids; D011422:Propionates; D008031:Lignin; D008780:Methyltransferases; C019608:caffeate O-methyltransferase; C495469:p-coumaric acid