Suppressed expression of O-methyltransferase gene imparts facilitated lignin biodegradation

in International Symposium (oral presentation paper), 國際研討會(全文口頭發表)
標題Suppressed expression of O-methyltransferase gene imparts facilitated lignin biodegradation
AuthorsHong-Lin Lee, 李鴻麟
會議名稱中華林學會95 年度學術論文發表會
出版日期Oct 13 2006 12:0

Biopulping has not been implemented into commercialization due to its inefficiency in lignin degradation. Here, using Liquidambar styraciflua (sweetgum) as a model, we show lignins with low syringyl-to-guaiacyl (S/G) ratios can be easily degraded by white rot fungi, Trametes versicolor. Agrobacterium-mediated genetic transformation and whole plant regeneration systems via nodular cultures were developed for sweetgum. Using these systems, sense aspen (Populus tremuloides)5-hydroxyconiferyl aldehyde O-methyltransferase (AldOMT) gene was transferred to sweetgum, and the field-grown transgenic trees at ages of three and six years were characterized. Pyrolysis GC-MS analyses revealed that transgenic trees were drastically reduced in lignin S/G ratio (0.54~0.96) as compared with control tree (1.80) and resulted in a significant lignin structural alteration in these transgenic trees. Molecular evidence of RT-PCR and western blotting with developing xylem tissues indicated that
lignin compositional changes were caused by co-suppression of the sweetgum endogenous AldOMT gene with the sense aspen transgene. Although the total lignin
content in these transgenics remained essentially unchanged, these transgenic lignins
could be degraded by Trametes versicolor with rates doubling the rate of degrading the wildtype lignin. Our results challenge the traditional wisdom that high lignin S/G ratio facilitates enzyme degradation of lignin and suggest that chemical linkages between S and G monomers in lignin play a more important role than the frequency of S and G constituents in determining the rate of lignin enzymatic degradability.

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