How Plants Make Lignin — Researchers Begin to Count the Ways

Lignin is a must for plants--it provides their structure and rigidity--but a headache for humans. For example, dairy producers don't like lignin because it reduces the digestibility of forages, the mainstay of U.S. dairy cow diets. And the paper industry spends millions of dollars annually on lignin removal and clean-up costs.

Agricultural Research Service scientists in Madison, Wis., say the next decade may bring relief in the form of a new kind of lignin--one that's easier for dairy cows to digest or for paper companies to extract.

John Ralph and Ron Hatfield of ARS' U.S. Dairy Forage Research Center in Madison are using a diagnostic analytical technology called nuclear magnetic resonance (NMR) to study a natural mutant pine tree discovered by North Carolina State researchers. The mutant tree is missing one of the enzymes thought necessary for lignin production. The absent enzyme--known as CAD--produces coniferyl alcohol, the main building block for making lignin in normal pine trees. Even though the mutant tree lacks this enzyme, it still produces lignin using two other simple compounds in a way researchers have never before described.

Thanks to the NMR technology, the ARS scientists have provided the first detailed description of the structure of this unusual lignin. They are now looking for traits in lignins to make them easier for the paper industry to pulp or for better digestibility in ruminant animals. This information will allow plant molecular geneticists to develop new plants with lignin that can be modified to suit specific needs.

Scientific contact: John Ralph or Ron Hatfield, U.S. Dairy Forage Research Center, Agricultural Research Service, USDA, Madison, WI 53706-1108. Phone (608) 264-5407 or (608) 264-5358, fax (608) 264-5147, jralph@facstaff.wisc.edu or rdhatfie@facstaff.wisc.edu.