Improvement of in-rumen digestibility of alfalfa forage by genetic manipulation of lignin O-methyltransferases |
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Authors: | Guo Dianging Chen Fang Wheeler John Winder John Selman Susan Peterson Michael Dixon Richard A |
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Institution: | (1) Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA;(2) Agricultural Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA;(3) W-L Research, Inc, 8701 W Highway 14, Evansville, WI 53536, USA |
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Abstract: | Lignin inhibits forage digestibility by ruminant animals, and lignin levels and the proportion of dimethylated syringyl (S) lignin monomers increase with progressive maturity in stems of forage crops. We generated transgenic alfalfa (Medicago sativa L.) with reduced lignin content and altered lignin composition. Down-regulation of caffeic acid 3-O-methyltransferase (COMT) reduces lignin content, accompanied by near total loss of S lignin, whereas down-regulation of caffeoyl coenzyme A 3-O-methyltransferase (CCoAOMT) reduces lignin content without reduction in S lignin. These changes are not accompanied by altered ratios of cell wall polysaccharides. Analysis of rumen digestibility of alfalfa forage in fistulated steers revealed improved digestibility of forage from COMT down-regulated plants, but a greater improvement in digestibility following down-regulation of CCoAOMT. The results indicate that both lignin content and composition affect digestibility of alfalfa forage, and reveal a new strategy for forage quality improvement by genetic manipulation of CCoAOMT expression. |
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Keywords: | fistulated steers forage digestibility lignification Medicago sativa O-methyltransferases transgenic plants |
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