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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Research » Publications at this Location » Publication #213436
Title: LIGNIFICATION IN TRANSGENICS DEFICIENT IN P-COUMARATE 3-HYDROXYLASE (C3H) AND THE ASSOCIATED HYDROXYCINNAMOYL TRANSFERASE (HCT)

Author
item Ralph, John
item AKIYAMA, TAKUYA - UNIV OF TOKYO
item KIM, HOON - UNIV OF WISCONSIN
item LU, FACHUANG - UNIV OF WISCONSIN
item RALPH, SALLY - U.S. FOREST PRODUCTS LAB
item CHAPPLE, CLINT - PURDUE UNIVERSITY
item NAIR, RAMESH - PURDUE UNIVERSITY
item CHEN, FANG - NOBLE FOUNDATION
item REDDY, SRINIVASA - NOBLE FOUNDATION
item DIXON, RICHARD - NOBLE FOUNDATION
item COLEMANN, HEATHER - UNIV OF BRITISH COLUMBIA
item MANSFIELD, SHAWN - UNIV OF BRITISH COLUMBIA

Submitted to: Physiologia Plantarum
Publication Type: Proceedings
Publication Acceptance Date: 4/1/2007
Publication Date: 8/12/2007
Citation: Ralph, J., Akiyama, T., Kim, H., Lu, F., Ralph, S.A., Chapple, C.C., Nair, R., Chen, F., Reddy, S., Dixon, R.A., Colemann, H.D., Mansfield, S.D. 2007. Lignification in transgenics deficient in p-coumarate 3-hydroxylase (C3H) and the associated hydroxycinnamoyl transferase (HCT). Physiologia Plantarum. 130(4):Abstract No. 10.

Interpretive Summary:

Technical Abstract: The effects on lignification of downregulating most of the genes for enzymes on the monolignol biosynthetic pathway have been reasonably well studied in angiosperms. The exception to this is the crucial hydroxylase, cinnamate 3-hydroxylase (C3H), and its associated hydroxycinnamyl transferase (HCT), taking p-coumarate to caffeate. Chapple's group discovered that an Arabidopsis mutant deficient in C3H produced no detectable guaiacyl (G) nor syringyl (S) lignin. Only p-hydroxyphenyl (H) units apparently derived from p-coumaryl alcohol could be detected. However, these particularly stunted plants were not readily able to provide sufficient cell wall material for more detailed structural analysis. The Noble Foundation has transformed commercially important alfalfa for improved digestibility and other traits. C3H-deficient plants have been analyzed, particularly by NMR, demonstrating that their lignins are derived from up to 65% of the normally minor (~1-3%) monolignol, p-coumaryl alcohol. As such, the lignification in these plants has been perturbed to a far higher degree than the previously studied perturbation known to enhance p-hydroxyphenyl levels, that occurring in softwood compression wood (where the level reaches about 10-30%). The structural ramifications are also being revealed, with significant variations from normal lignins in the control plants. Mansfield's group has generated C3H-deficient poplar. They appear to have a different monolignol profile from the alfalfa transgenics.