Submitted to: International Symposium on Wood and Pulping Chemistry
Publication Type: Proceedings
Publication Acceptance Date: 2/28/2003
Publication Date: 6/8/2003
Citation: MARITA, J.M., RALPH, J., HATFIELD, R.D., GUO, D., CHEN, F., DIXON, R. MODIFICATIONS IN LIGNIN OF TRANSGENIC ALFALFA DOWN-REGULATED IN COMT AND CCOAOMT. INTERNATIONAL SYMPOSIUM ON WOOD AND PULPING CHEMISTRY. 2003. Interpretive Summary:
Technical Abstract: Alfalfa (Medicago sativa L.) is a leading forage crop. It has high nutritive value because it is rich in protein, minerals, and vitamins, and if harvested prior to flowering can retain a low fiber and high energy content. The intake and digestibility of forage by dairy animals directly affect their production of meat and milk. A reduction in feeding value results from a lower leaf to stem ratio and the deposition of lignin and polysaccharides in stem cell walls during maturation. The present study examined the alterations to alfalfa lignin structure and composition resulting from independent down-regulation of caffeic acid 3-O-methyltransferase (COMT) and caffeoyl Coenzyme A 3-O-methyltransferase (CCoAOMT) two key enzymes in the lignin pathway. Previous work has shown genetically modified alfalfa to have altered lignin composition and improved in situ digestibility. The results of this study reveal new details of the incorporation of novel units in the lignin of COMT-deficient alfalfa including units not previously identified and an increase in the cellulose:lignin ratio in CCoAOMT-deficient alfalfa. This information allows researchers insight into which lignin structural modifications positively impact alfalfa digestibility.