Manipulation of Lignin Biosynthesis

One of the main thrusts of modern plant biology is to understand the specific role of different genes in plant development. In many biological systems, mutant organisms have proved to be powerful tools for addressing this question. In plants, a variety of reverse genetic techniques can be employed, via transgenesis, to make mutants with specific changes to plant metabolism or development. We are using some of these techniques to investigate the process of lignification, a specific developmental programme unique to plants. A second strand of our research is to develop new and improved techniques, or enabling technologies, to broaden the possibilities for manipulating plant metabolism by transgenesis.

Lignin is an essential component of the wall of certain cell types in land plants. Although the pathway for lignin biosynthesis was outlined many years ago, important basic features are still poorly understood. The spatial organisation of the pathway, how it is regulated, and even the exact sequence of enzymes involved, are all areas of intensive current research. We have produced a library of transgenic plants with altered lignification by manipulating the expression of particular single genes or combinations of genes. We are currently using these mutants to better understand how the lignin pathway operates in vivo and to investigate the biochemistry, cell biology and molecular biology of lignin synthesis. Our mutants are also revealing roles for the lignin pathway in unexpected areas of plant development.

In addition, as lignin is a major component of wood and has significant commercial importance, our work has application to the improvement of plant materials for industrial and agricultural uses.

Most work to date on the manipulation of plant metabolic pathways has concentrated on modulating the expression of single genes. However full exploitation of reverse genetics as a tool for basic and applied plant research will depend on the ability to co-ordinately manipulate multiple genes. We are developing strategies for one-step over-expression or down-regulation of multiple genes in plants. We are also attempting to develop a system for performing gene targeting, or gene 'knock-outs', in plants. Although this technique has proved extremely useful in animal research, no-one has yet been able to adapt it to plants. We are addressing some of the problems that prevent gene targeting in plants in order to move towards the development of an effective protocol.