Transgenic barley expressing a fungal xylanase gene in the endosperm of the developing grains

The feasibility of producing plant cell wall polysaccharide-hydrolysing fee d enzymes in the endosperm of barley grain was investigated. The coding reg ion of a modified xylanase gene (xynA) from the rumen fungus, Neocallimasti x patriciarum, linked with an endosperm-specific promoter from cereal stora ge protein genes was introduced into barley by Agrobacterium-mediated trans formation. Twenty-four independently transformed barley lines with the xyla nase gene were produced and analysed. The fungal xylanase was produced in t he developing endosperm under the control of either the rice glutelin B-1 ( GluB-1) or barley B1 hordein (Hor2-4) promoter. The rice GluB-1 promoter pr ovided an apparently higher expression level of recombinant proteins in bar ley grain than the barley Hor2-4 promoter in both transient and stable expr ession experiments. In particular, the mean value for the fungal xylanase a ctivity driven by the GluB-1 promoter in the mature grains of transgenic ba rley was more than twice that with the Hor2-4 promoter. Expression of the x ylanase transgene under these endosperm-specific promoters was not observed in the leaf, stem and root tissues. Accumulation of the fungal xylanase in the developing grains of transgenic barley followed the pattern of storage protein deposition. The xylanase was stably maintained in the grain during grain maturation and desiccation and post-harvest storage. These results i ndicate that the cereal grain expression system may provide an economic mea ns for large scale production of feed enzymes in the future.