Plant & Animal Genomes XIV Conference

January 14-18, 2006
Town & Country Convention Center
San Diego, CA

Manipulating Cell Wall Phenolic Composition By Targeted Expression Of Fungal Enzymes Towards More Digestible Grasses

Marcia M. de O. Buanafina , Tim Langdon , Susan Dalton , Barbara Hauck , Phillip Morris

  Plant Animal Microbial Science Department IGER- Institute of Grassland and Environmental Research Aberystwyth Ceredigion, SY23 3EB Wales, UK

Recombinant DNA technology provides a valuable tool for genome manipulation and crop improvement. Numerous studies have shown that ferulic acid (4-hydroxy-3-methoxy-cinnamic acid), the most abundant hydroxycinnamic acid in grass cell walls, acts as a cross-linking agent between carbohydrates and between carbohydrates and lignin and is among the factors most inhibitory to the biodegradation of plant cell wall carbohydrates. Reducing the level of ferulates is therefore a predictable way to increase the degradation of cell wall polymers and consequently the rate and extent of grass digestibility.
We have produced Festuca arundinacea plants expressing a ferulic acid esterase gene (FAE) from Aspergillus niger and demonstrated its potential to break phenolic cross-linking from solubilized plant cell wall. This was enhanced several fold by the exogenous addition of recombinant Trichoderma ß-1,4-endo-xylanase (Buanafina et al., 2002) in vacuole targeted FAE plants.
We show here that it is possible to genetically modify the levels of cell wall phenolics and digestibility in grasses by inducible expression of FAE targeted to apoplast, ER and golgi. Whether the synergistic interaction between Aspergillus ferulic acid esterase and Trichoderma xylanase on the release of cell wall ferulates by co-expressing them in grasses could increase further the release of cell wall ferulates and have a greater effect on the release of reducing sugars, consequently increasing the biodegradability of grasses cell wall carbohydrates, will be addressed by co-expressing endo-ß-1,4-xylanase from Trichoderma reesei targeted to the apoplast under a senescence promoter in Festuca arundinacea plants expressing apoplast targeted FAE.
Buanafina, M.M de O., Langdon, T., Hicks, H., Hauck, B., Dalton, S.J. and Morris, P. In: Proc. 19th European Grassland Federation – General Meeting La Rochelle (France) 27030 May 2002. Pg. 66- 67.