Lignins are complex three-dimensional phenolic polymers that are embedded in the cell walls of specialised plant cells. Lignins function as inter- and intra-molecular glues, rigidifying the plant cell walls in which they are embedded. Lignins are hydrophobic, and render cell walls impermeable to water. The complex nature of lignins makes them difficult to degrade; therefore, lignified cell walls are more resistant to enzymatic hydrolysis. As a consequence of these different properties, lignins play important roles in mechanical support, water transport, and disease resistance in plants. The spatial and temporal control of lignin biosynthesis, known as lignification, is extremely important. Lignification is a metabolically costly process that requires large quantities of carbon skeletons and reducing equivalents. Plants do not possess a mechanism to degrade lignins, so any carbon invested in lignin biosynthesis is not recoverable. Consequently, lignified cells represent a significant, non-recoverable carbon sink. As such, plants must carefully balance the requirement for lignification against the availability of resources to synthesise lignin polymers. Moreover, as lignin restricts the expansion of the cell wall, lignification must occur after a cell has undergone division and expansion growth. Given the metabolic cost of making the lignin polymer, coupled with its persistence and cell rigidifying properties, the timing and localisation of lignification must be tightly regulated. Therefore, mechanisms must be in place to regulate the lignin biosynthetic pathway.

Dr. Campbell and his research group have examined the regulation of lignification using several complementary approaches. In the last decade, Dr. Campbell was involved in instrumental and widely-cited studies that elucidated the roles of key biosynthetic enzymes in the lignin biosynthetic pathway. This work included one of the first instances of the modification of lignification using genetic engineering, and the detailed characterisation of a mutant pine tree harbouring a null mutation for a gene encoding an enzyme in the lignin biosynthetic pathway. Dr. Campbell's group has continued to use both genetic engineering and mutant analysis to characterise the factors involved in the regulation of lignification. Recent work has included transcript profiling of arabidopsis mutants with abnormal patterns of lignin deposition, and the genetic modification of transcription factors implicated in lignin biosynthesis. Several publications reporting the latter work, based largely on a recently completed Ph.D. thesis, have been written.

Personnel:

Dr. Christian Dubos

Publications (personnel supervised by Dr. Campbell are underlined):

Newman LJ, Perazza D, Juda L, Campbell MM (2004) Involvement of the R2R3-MYB, AtMYB61, in the ectopic lignification and dark-photomorphogenic components of the det3 mutant phenotype. The Plant Journal 37:239-250, doi:10.1046/j.1365-313X.2003.01953.x (BBSRC funded)

Rogers L, Dubos C, Mansfield S, Surman C, Willment J, Campbell MM. Mechanisms governing lignin deposition revealed through the comparison of three distinct ectopic lignification mutants. (submitted to The Plant Journal, under review) (BBSRC funded)

Rogers L, Campbell MM. Tansley Review: The genetic control of lignin deposition during plant growth and development. New Phytologist (in press) doi:10.1111/j.1469-8137.2004.01143.x (BBSRC funded)