Phenolic compounds in ectomycorrhizal interaction of lignin modified silver birch.
BACKGROUND
The monolignol biosynthetic pathway interconnects with the biosynthesis of other secondary phenolic metabolites, such as cinnamic acid derivatives, flavonoids and condensed tannins. The objective of this study is to evaluate whether genetic modification of the monolignol pathway in silver birch (Betula pendula Roth.) would alter the metabolism of these phenolic compounds and how such alterations, if exist, would affect the ectomycorrhizal symbiosis.


RESULTS
Silver birch lines expressing quaking aspen (Populus tremuloides L.) caffeate/5-hydroxyferulate O-methyltransferase (PtCOMT) under the 35S cauliflower mosaic virus (CaMV) promoter showed a reduction in the relative expression of a putative silver birch COMT (BpCOMT) gene and, consequently, a decrease in the lignin syringyl/guaiacyl composition ratio. Alterations were also detected in concentrations of certain phenolic compounds. All PtCOMT silver birch lines produced normal ectomycorrhizas with the ectomycorrhizal fungus Paxillus involutus (Batsch: Fr.), and the formation of symbiosis enhanced the growth of the transgenic plants.


CONCLUSIONS
The down-regulation of BpCOMT in the 35S-PtCOMT lines caused a reduction in the syringyl/guaiacyl ratio of lignin, but no significant effect was seen in the composition or quantity of phenolic compounds that would have been caused by the expression of PtCOMT under the 35S or UbB1 promoter. Moreover, the detected alterations in the composition of lignin and secondary phenolic compounds had no effect on the interaction between silver birch and P. involutus.
Department of Biology, University of Oulu, 90014 Oulu, Finland. suvi.sutela@oulu.fi
Suvi
S
Sutela
Karoliina
K
Niemi
Jaanika
J
Edesi
Tapio
T
Laakso
Pekka
P
Saranpää
Jaana
J
Vuosku
Riina
R
Mäkelä
Heidi
H
Tiimonen
Vincent L
VL
Chiang
Janne
J
Koskimäki
Marja
M
Suorsa
Riitta
R
Julkunen-Tiitto
Hely
H
Häggman
D029662:Betula / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D018506:Gene Expression Regulation, Plant; D008031:Lignin / Q000096:biosynthesis*; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism; D038821:Mycorrhizae / Q000502:physiology*; D010636:Phenols / Q000378:metabolism*; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D032107:Populus / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D017422:Sequence Analysis, DNA; D013559:Symbiosis; D013634:Tannins / Q000096:biosynthesis
D010636:Phenols; D018749:RNA, Plant; D013634:Tannins; D008031:Lignin; D008780:Methyltransferases; C019608:caffeate O-methyltransferase