Scientists at the University of Manchester have identified two genes that cause plants to grow outward and believe the research could be used to increase the biomass of trees used to produce bioenergy and for other purposes.

Professor Simon Turner said the project, funded by the Biotechnology and Biological Sciences Research Council, began in 2003 with the initial intent of discovering how plants control the way in which cells divide. Turner and UM researcher Peter Etchells studied the plant Adrabidopsis, which has a vascular system similar to that of a tree, in order to investigate the growth in its vascular bundles. They found that genes PXY and CLE41 directed the amount and direction of cell division, and by overexpressing CLE41, they saw a greater amount of growth. "We found that overexpressing one gene gives more cells, but they were very disorganized and not useful because the orientation is affected," Turner said. "By understanding how the two genes control both the amount of cell division and the orientation of division that allows us to manipulate it in a useful way."

Turner said it is difficult to quantify how much mass can be increased in Arabidopsis by gene manipulation, because some tissue undergo cell divisions and radial growth that do not normally divide. "In vascular bundles, there are somewhere between two and three times as many cells," he said. The team is now growing poplar trees in a laboratory to determine whether they fit the Arabidopsis model, and hope to use the results to develop a system to increase wood production.

As far as applicability toward other crops goes, Turner said apart from trees, the researchers know the method works in tobacco, and although tobacco is not currently grown as a biomass crop, that fact has instilled confidence in the researchers that it will work in any dicot crop, such as soybeans or alfalfa. Dicots are flowering plants that have two embryonic leaves or cotyledons, while monocots have one embryonic leaf. "What will happen in monocots such as maize or switchgrass is less clear, but we are currently testing this," he said.

The research paper, called "The PXY-CLE41 receptor ligand pair defines a multifunctional pathway that controls the rate and orientation of vascular cell division," was published online Feb. 10 in Development journal.