NMR characterization of lignins in Arabidopsis altered in the activity of ferulate 5-hydroxylase.
Nuclear magnetic resonance (NMR) of isolated lignins from an Arabidopsis mutant deficient in ferulate 5-hydroxylase (F5H) and transgenic plants derived from the mutant by overexpressing the F5H gene has provided detailed insight into the compositional and structural differences between these lignins. Wild-type Arabidopsis has a guaiacyl-rich, syringyl-guaiacyl lignin typical of other dicots, with prominent beta-aryl ether (beta-O-4), phenylcoumaran (beta-5), resinol (beta-beta), biphenyl/dibenzodioxocin (5-5), and cinnamyl alcohol end-group structures. The lignin isolated from the F5H-deficient fah1-2 mutant contained only traces of syringyl units and consequently enhanced phenylcoumaran and dibenzodioxocin levels. In fah1-2 transgenics in which the F5H gene was overexpressed under the control of the cauliflower mosaic virus 35S promoter, a guaiacyl-rich, syringyl/guaiacyl lignin similar to the wild type was produced. In contrast, the isolated lignin from the fah1-2 transgenics in which F5H expression was driven by the cinnamate 4-hydroxylase promoter was almost entirely syringyl in nature. This simple lignin contained predominantly beta-aryl ether units, mainly with erythro-stereochemistry, with some resinol structures. No phenylcoumaran or dibenzodioxocin structures (which require guaiacyl units) were detectable. The overexpression of syringyl units in this transgenic resulted in a lignin with a higher syringyl content than that in any other plant we have seen reported.
Marita
J M
JM
United States Dairy Forage Research Center, United States Department of Agriculture, Agricultural Research Service, Madison, WI 53706-1108, USA.
Ralph
J
J
Hatfield
R D
RD
Chapple
C
C
D017360:Arabidopsis / Q000737:chemistry* / Q000201:enzymology; D029681:Arabidopsis Proteins; D003577:Cytochrome P-450 Enzyme System; D008031:Lignin / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000737:chemistry / Q000201:enzymology
D029681:Arabidopsis Proteins; D010940:Plant Proteins; D008031:Lignin; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C097486:CYP84A1 protein, Arabidopsis