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The Arabidopsis cinnamoyl CoA reductase irx4 mutant has a delayed but coherent (normal) program of lignification
Author(s) -
Laskar Dhrubojyoti D.,
Jourdes Michaël,
Patten Ann M.,
Helms Gregory L.,
Davin Laurence B.,
Lewis Norman G.
Publication year - 2006
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2006.02918.x
Subject(s) - lignin , mutant , arabidopsis , heteronuclear molecule , chemistry , heteronuclear single quantum coherence spectroscopy , biochemistry , arabidopsis thaliana , wild type , stereochemistry , two dimensional nuclear magnetic resonance spectroscopy , organic chemistry , nuclear magnetic resonance spectroscopy , gene
Summary Previous studies have indicated that the Arabidopsis thaliana irregular xylem 4 ( irx4 ) mutant is severely lignin‐deficient, forming abnormal lignin from aberrant monomers. Studies of lignin structure in dwarfed cinnamoyl CoA reductase (CCR)‐downregulated tobacco were also previously reported to incorporate feruloyl tyramine derivatives. The lignin in the Arabidopsis irx4 mutant was re‐investigated at 6 weeks and at maturation (9 weeks). Application of 1 H, 13 C, 2D Heteronuclear Multiple Quantum Coherence and 2D Heteronuclear Multiple Bond Coherence spectroscopic analyses to the lignin‐enriched isolates from both Arabidopsis wild‐type (L er ) and the CCR‐ irx4 mutant at both developmental stages revealed that only typical guaiacyl/syringyl lignins were formed. For the irx4 mutant, the syringyl content at 6 weeks growth was lower, in accordance with a delayed but coherent program of lignification. At maturation, however, the syringyl/guaiacyl ratio of the irx4 mutant approached that of wild‐type. There was no evidence for feruloyl tyramines, or homologues thereof, accumulating as a chemical signature in lignins resulting from CCR mutation. Nor were there any noticeable increases in other phenolic components, such as hydroxycinnamic acids. These findings were further confirmed by application of thioacidolysis, alkaline nitrobenzene oxidation and acetyl bromide analyses. Moreover, in the case of CCR downregulation in tobacco, there were no NMR spectroscopic correlations that demonstrated feruloyl tyramines being incorporated into the lignin biopolymers. This study thus found no evidence that abnormal lignin formation occurs when CCR activity is modulated.

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