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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Research » Publications at this Location » Publication #96506
Title: REPRESSION OF LIGNIN BIOSYNTHESIS PROMOTES CELLULOSE ACCUMULATION AND GROWTH IN TRANSGENIC TREES

Author
item HU, WEN-JING - MICHIGAN TECH-HOUGHTON MI
item LUNG, JRHAU - MICHIGAN TECH-HOUGHTON MI
item HARDING, SCOTT - MICHIGAN TECH-HOUGHTON MI
item POPKO, JACQUELINE - MICHIGAN TECH-HOUGHTON MI
item Ralph, John
item STOKKE, DOUGLAS - MICHIGAN TECH-HOUGHTON MI
item TSAI, CHUNG-JUI - MICHIGAN TECH-HOUGHTON MI
item CHIANG, VINCENT - MICHIGAN TECH-HOUGHTON MI

Submitted to: Nature Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: A major component in all plants, lignin is a complex component that limits digestion of plants by animals, and is what must be removed from wood to make paper. There has been interest recently in using genetic biotechnologies to knock out specific genes that produce crucial precursors of lignin. Producing viable plants with less lignin and, ideally, more cellulose, has been a goal of many researchers aiming to improve plant utilization. Workers at Michigan Tech have decreased the expression (down- regulated) of a specific lignin-producing gene in poplar trees. In these remarkable down-regulated transgenic aspen plants, the lignin has been reduced by about 45%, and cellulose has increased by 15% in compensation. Studies at the Dairy Forage Research Center show this lignin to be strikingly normal; the lignin does not contain unexpected new components that have been seen in other transgenic and mutant plants deficient in lignin genes. Unexpectedly, the plants show marked growth acceleration as well. These plants, with about twice the cellulose to lignin ratio as normal aspen, are potentially superior for pulp and paper production (which separates the useful cellulose fibers from lignin for paper production); there are, however, many aspects which need researching before such trees are commercially available, but the promise shown by these transgenic plants is encouraging. Similar genetic transformations in forage crop plants may also improve digestibility by ruminants, potentially reducing animal wastes. Such studies are at the heart of efforts to improve agricultural sustainability and maximize our plant resources.

Technical Abstract: Lignin and cellulose comprise 70% of wood mass and are responsible for the mechanical strength of trees. Transgenic aspen (Populus tremuloides) with suppressed expression of a lignin pathway gene (Pt4CL1) encoding 4-coumaric acid:coenzyme A ligase exhibited up to a 45% reduction of lignin, which was compensated for by a 15% increase in cellulose. As a result, the total lignin-cellulose mass remain unchanged. Structural integrity was maintaine and leaf, root and stem growth increased. The reduction of lignin with a concomitant increase in cellulose indicate that the deposition of these two structural components in trees may be regulated in a compensatory fashion not reported in herbaceous plants where altered lignin or cellulose biosynthesis often lead to loss of cellular structural integrity and to abnormal growth. Such regulation may provide metabolic flexibility to sustain the long term structural integrity of woody perennials.