|Over-expression of the CLE41 gene (right) results in more woody tissue production.
“The United States has set the ambitious goal of generating a third of all liquid fuel from renewable sources by the year 2025. Estimates suggest to reach their goal they would need 1 billion tonnes of biomass, which is a lot,” says professor Simon Turner, one of the University of Manchester researchers whose study, funded by the Biotechnology and Biological Sciences Research Council, study was published in the journal Development on February 10, 2010.
“Our work has identified the two genes that make plants grow outwards. The long, thin cells growing down the length of a plant divide outwards, giving that nice radial pattern of characteristic growth rings in trees. So you get a solid ring of wood in the centre surrounded by growing cells. Now we have identified the process by which the cells know how to grow outwards, we hope to find a way of making that plants grow thicker quicker, giving us the increased wood production that could be used for biofuels or other uses.”
“And there is an added benefit. There are concerns that the growing of biofuel products competes with essential food production. However, the part of the plant we have studied is the stalk, not the grain, so there will be no competition with food production.”
Turner and Dr. Peter Etchells, at the Faculty of Life Sciences, studied the plant Arabidopsis, which does not look like a tree but has a similar vascular system to carry water and sugar throughout the plant. They investigated growth in the vascular bundles and found that the genes PXY and CLE41 directed the amount and direction of cell division. Furthermore, they found that over-expression of CLE41 caused a greater amount of growth in a well-ordered fashion, thus increasing wood production.
“We wanted to know how the cells divided to produce this pattern, how they ‘knew’ which side to divide along, and we found that it was down to the interaction of these two genes,” says Turner.
“Trees are responsive to a lot of things. They stop growing in winter and start again in spring, and this changes according to the amount of light and the day length. It might take a tree 150 years to grow in Finland and only 10 years in Portugal. Now we know what genes are dictating the growth process, we can develop a system of increasing growth so that it is orientated to produce more wood – increasing the essential biomass needed for our future.”
The team is now growing poplar trees in the lab to see if they fit the Arabidopsis model. They will use these results to develop a system of increasing wood production.