UK-Brazil partnership.

The proposal is for a small project which, if successful, would represent a major step forward in our understanding of genes controlling cell wall properties of grasses, which include not only grassland crops but also major food crops such as wheat, rice and sugar cane. These cell walls represent the great majority of biomass in grass vegetation and therefore are the main constituent of by-products of crop food production such as cereal straw and sugar cane residues. If they could be made more digestible, these huge amounts of biomass would become more valuable for bioethanol production and for animal feed. It is believed that feruloylation in grass cell walls makes them less digestible by linking the polysaccharide sugars to lignin, which inhibits digestion. However the genes responsible for feruloylation are unknown. We have identified candidate genes in the BAHD gene family and have designed a DNA sequence to specifically suppress the acitivity of these genes in a model grass species (Brachypodium distachyon). The proposed work is to introduce this sequence into the Brachypodium plants and then compare the GM plants with control plants. We will therefore determine if feruloylation has been decreased by suppressing the BAHD genes. If it has, these plants will become invaluable tools for studying feruloylation of cell walls and the way it affects the properties of the cell walls. In particular, we will study the impact on digestibility of biomass.

The proposal is for a small project which, if successful, would represent a major step forward in our understanding of genes controlling grass cell wall properties. These cell walls represent the great majority of biomass in grass vegetation and by-products of crop food production such as wheat straw and sugar cane residues. If they could be made more digestible, these huge amounts of biomass would become more valuable for bioethanol production and for animal feed. It is believed that feruloylation in grass cell walls makes them less digestible by linking the polysaccharide sugars to lignin, which inhibits digestion. However the genes responsible for feruloylation are unknown. In a previous project, we have already identified all the candidate genes within the BAHD family that are highly expressed in Brachypodium distachyon. An RNAi construct has been designed to specifically suppress expression of all 8 of these genes in Brachypodium. Two versions of this RNAi construct have been created, one driven by a constitutive promoter and one by a IRX3-1.5kb upstream region isolated from Brachypodium which we expect to act as a strong secondary cell wall specific promoter. The proposed work is to transform Brachypodium plants with these constructs and then analyse the cell wall feruloylation using a protocol that we have already applied extensively to Brachypodium tisssues. We will therefore determine if feruloylation has been decreased by suppressing the BAHD genes. If it has, these plants will become invaluable tools for studying feruloylation of cell walls and the way it affects the properties of the cell walls. In particular, we will study the impact on digestibility of biomass as part of a wide investigation of the cell walls of the transgenic plants.

Societal:
Since use of lignocellulose feedstock for biofuel has far greater benefits for CO2 emissions than starch or sugar, a successful outcome in showing a means for increasing digestibility of grass biomass would be a step towards reducing emissions in Brazil and UK and would reduce competition between food and fuel for land.

Academic:
Grass cell walls are a topic of great interest worldwide and the major evolutionary division between dicots and grasses is in the feruloylation of xylan in grass cell walls. Therefore definitive evidence that the BAHD gene candidates are responsible for feruloylation would have major importance for our understanding of evolution of cell walls and would be a high impact publication.

Commercial:
Identification of genes responsible for feruloylation may open opportunites for developing new varieties with increased digestibility of biomass for animal feed.