title: Gene silencing of cinnamyl alcohol dehydrogenase in Pinus radiata callus cultures.
abstract: Xylem-derived Pinus radiata cell cultures, which can be induced to differentiate tracheary elements (TEs), were transformed with an RNAi construct designed to silence cinnamyl alcohol dehydrogenase (CAD), an enzyme involved in the biosynthesis of monolignols. Quantitative enzymatic CAD measurements revealed reduced CAD activity levels in most transclones generated. TEs from transclones with approximately 20% residual CAD activity did not release elevated levels of vanillin, which was derived from coniferyl-aldehyde through a mild alkali treatment. However, the activation of the phenylpropanoid pathway in transclones with approximately 20% residual CAD activity through the application of non-physiological concentrations of sucrose and l-phenylalanine produced phenotypic changes. The accumulation of metabolites such as dihydroconiferyl-alcohol (DHCA), which also accumulates in the P. taeda CAD mutant cad-n1, was observed. These results indicate that a substantial reduction in CAD activity is necessary for this enzyme to become a rate-limiting step in lignin biosynthesis in conifers such as P. radiata and confirm that transformable P. radiata callus cultures can be useful to investigate the function of xylogenesis-related genes in conifers.
authors.affiliation: Cellwall Biotechnology Centre (CBC), Forest Research, Private Bag 3020, Rotorua, New Zealand.
authors.forename: Ralf
authors.initials: R
authors.lastname: Möller
authors.forename: Diane
authors.initials: D
authors.lastname: Steward
authors.forename: Lorelle
authors.initials: L
authors.lastname: Phillips
authors.forename: Heather
authors.initials: H
authors.lastname: Flint
authors.forename: Armin
authors.initials: A
authors.lastname: Wagner
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D002478:Cells, Cultured; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D006720:Homozygote; D008031:Lignin / Q000096:biosynthesis*; D009154:Mutation; D010636:Phenols / Q000378:metabolism; D028223:Pinus / Q000201:enzymology* / Q000235:genetics; D041603:Pinus taeda / Q000201:enzymology / Q000235:genetics; D034741:RNA, Small Interfering / Q000378:metabolism
chemical_list: D010636:Phenols; D034741:RNA, Small Interfering; C106832:dihydroconiferyl alcohol; D008031:Lignin; D000429:Alcohol Oxidoreductases; C018656:cinnamyl alcohol dehydrogenase