title: Phenolic compounds and expression of 4CL genes in silver birch clones and Pt4CL1a lines.
abstract: A small multigene family encodes 4-coumarate:CoA ligases (4CLs) catalyzing the CoA ligation of hydroxycinnamic acids, a branch point step directing metabolites to a flavonoid or monolignol pathway. In the present study, we examined the effect of antisense Populus tremuloides 4CL (Pt4CL1) to the lignin and soluble phenolic compound composition of silver birch (Betula pendula) Pt4CL1a lines in comparison with non-transgenic silver birch clones. The endogenous expression of silver birch 4CL genes was recorded in the stems and leaves and also in leaves that were mechanically injured. In one of the transgenic Pt4CL1a lines, the ratio of syringyl (S) and guaiacyl (G) lignin units was increased. Moreover, the transcript levels of putative silver birch 4CL gene (Bp4CL1) were reduced and contents of cinnamic acid derivatives altered. In the other two Pt4CL1a lines changes were detected in the level of individual phenolic compounds. However, considerable variation was found in the transcript levels of silver birch 4CLs as well as in the concentration of phenolic compounds among the transgenic lines and non-transgenic clones. Wounding induced the expression of Bp4CL1 and Bp4CL2 in leaves in all clones and transgenic lines, whereas the transcript levels of Bp4CL3 and Bp4CL4 remained unchanged. Moreover, minor changes were detected in the concentrations of phenolic compounds caused by wounding. As an overall trend the wounding decreased the flavonoid content in silver birches and increased the content of soluble condensed tannins. The results indicate that by reducing the Bp4CL1 transcript levels lignin composition could be modified. However, the alterations found among the Pt4CL1a lines and the non-transgenic clones were within the natural variation of silver birches, as shown in the present study by the clonal differences in the transcripts levels of 4CL genes, soluble phenolic compounds and condensed tannins.
authors.affiliation: Department of Biology, University of Oulu, Oulu, Finland.
authors.forename: Suvi
authors.initials: S
authors.lastname: Sutela
authors.affiliation: Department of Biology, University of Oulu, Oulu, Finland.
authors.forename: Terhi
authors.initials: T
authors.lastname: Hahl
authors.affiliation: The Finnish Border Guard, Border and Coast Guard Academy, Imatra, Finland.
authors.forename: Heidi
authors.initials: H
authors.lastname: Tiimonen
authors.affiliation: Finnish Forest Research Institute, Eastern Finland Regional Unit (Punkaharju Unit), Punkaharju, Finland.
authors.forename: Tuija
authors.initials: T
authors.lastname: Aronen
authors.affiliation: Finnish Forest Research Institute, Southern Finland Regional Unit (Vantaa Unit), Vantaa, Finland.
authors.forename: Tiina
authors.initials: T
authors.lastname: Ylioja
authors.affiliation: Finnish Forest Research Institute, Southern Finland Regional Unit (Vantaa Unit), Vantaa, Finland.
authors.forename: Tapio
authors.initials: T
authors.lastname: Laakso
authors.affiliation: Finnish Forest Research Institute, Southern Finland Regional Unit (Vantaa Unit), Vantaa, Finland.
authors.forename: Pekka
authors.initials: P
authors.lastname: Saranpää
authors.affiliation: Forest Biotechnology Group, Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, North Carolina, United States of America.
authors.forename: Vincent
authors.initials: V
authors.lastname: Chiang
authors.affiliation: Department of Biology, University of Eastern Finland, Joensuu, Finland.
authors.forename: Riitta
authors.initials: R
authors.lastname: Julkunen-Tiitto
authors.affiliation: Department of Biology, University of Oulu, Oulu, Finland.
authors.forename: Hely
authors.initials: H
authors.lastname: Häggman
mesh_terms: D029662:Betula / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D001696:Biomechanical Phenomena; D003001:Cloning, Molecular; D003066:Coenzyme A Ligases / Q000172:deficiency / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D010636:Phenols / Q000737:chemistry / Q000378:metabolism*; D018515:Plant Leaves / Q000235:genetics; D030821:Plants, Genetically Modified; D032107:Populus / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012995:Solubility
chemical_list: D010636:Phenols; D012333:RNA, Messenger; D003066:Coenzyme A Ligases; C019943:4-coumarate-CoA ligase