Choice Solved: Grasses for Food, Fuel

Tuesday, January 17, 2012 @ 01:01 PM gHale


The search for a quality way to produce energy and take away from the dependence on oil is now leading to a family of genes that could help breed grasses to improve properties for diet and bioenergy.

The genes are important in the development of the fibrous, woody parts of grasses, like rice and wheat, said researches from the Biotechnology and Biological Sciences Research Council (BBSRC) Sustainable Bioenergy Centre (BSBEC).

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This team hopes by understanding how these genes work, they might for example be able to breed varieties of cereals where the fibrous parts of the plants confer dietary benefits or crops whose straw requires less energy-intensive processing in order to produce biofuels.

The majority of the energy stored in plants is within the woody parts, and billions of tons of this material come from global agriculture each year in growing cereals and other grass crops, but this energy remains tightly locked away and hard to get at. This research could offer the possibility of multi-use crops where the grain part could be food and feed, while the straw parts used to produce energy efficiently. This help alleviate the issue of whether to use plants for food or fuel. This way you could use the one plant for both.

“Unlike starchy grains, the energy stored in the woody parts of plants is locked away and difficult to get at,” said Professor Paul Dupree, of the University of Cambridge. “Just as cows have to chew the cud and need a stomach with four compartments to extract enough energy from grass, we need to use energy-intensive mechanical and chemical processing to produce biofuels from straw.

“What we hope to do with this research is to produce varieties of plants where the woody parts yield their energy much more readily – but without compromising the structure of the plant. We think that one way to do this might be to modify the genes that are involved in the formation of a molecule called xylan – a crucial structural component of plants.”

Xylan is an important, highly-abundant component of the tough walls that surround plant cells. It holds the other molecules in place and helps to make a plant robust and rigid. This rigidity is important for the plant, but locks in the energy needed to produce bioenergy efficiently.

Grasses contain a substantially different form of xylan to other plants. The team wanted to find out what was responsible for this difference and so looked for genes turned on much more regularly in grasses than in the model plant Arabidopsis. Once they had identified the gene family in wheat and rice, called GT61, they were able transfer it into Arabidopsis, which in turn developed the grass form of xylan.

“As well as adding the GT61 genes to Arabidopsis, we also turned off the genes in wheat grain,” said Dr Rowan Mitchell of Rothamsted Research. “Both the Arabidopsis plants and the wheat grain appeared normal, despite the changes to xylan. This suggests that we can make modifications to xylan without compromising its ability to hold cell walls together. This is important as it would mean that there is scope to produce plant varieties that strike the right balance of being sturdy enough to grow and thrive, whilst also having other useful properties such as for biofuel production.”

The tough, fibrous parts of plants are also an important component of the diet as fiber. Fiber has a well established role in a healthy diet, for example, by lowering blood cholesterol. The team already showed changing GT61 genes in wheat grain affects the dietary fiber properties so this research also offers the possibility of breeding varieties of cereals for producing foods with enhanced health benefits.

“Recent reports have underlined the important role that bioenergy can play in meeting our future energy needs – but they all emphasize that sustainability must be paramount,” said Duncan Eggar, BBSRC Bioenergy Champion.

“Central to this will be ensuring that we can get energy efficiently from woody sources that need not compete with food supply. This research demonstrates how, by understanding the fundamental biology of plants, we can think about how to produce varieties of crops with useful traits, specifically for use as a source of energy.”



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