The research program in my lab is largely directed toward understanding how plant cell wall polysaccharides are synthesized, how the structures relate to the functions of the cell wall, and how the system is regulated. I envision that knowledge of cell wall structure and function will facilitate the development of plants with improved utility as sources of renewable materials and as biofuel feedstocks. Here is a link to a talk The future of Biofuels (in powerpoint format) that I presented at the Carnegie Institution in Washington on May 06, 2006.

A major focus of work in the lab is in understanding how cellulose is made. We have developed plants in which cellulose synthase is modified in various ways that facilitate functional studies. One type of modification is the addition of yellow fluorescent protein to subunits of the complex. This allows imaging of the complexes in live cells. We have used this capability to show that an interaction between cellulose synthase and cortical microtubules controls the orientation of cellulose deposition. We are engaged in understanding what regulates the amount of cellulose and the properties of cellulose microfibrils (eg., length and diameter). We have also developed plants that express cellulose synthases with other modifications that will facilitate structural studies of isolated complexes.

A second line of work in the lab concerns the identification of the genes for enzymes that catalyze synthesis of the major polysaccharides. We have identified a number of mutants with altered polysaccharide composition. In order to facilitate the analysis of such mutants we have been developing new tools for polysaccharide analysis. One class of new tools, developed by postdoc Stefan Bauer in collaboration with Prasanna Vasu (Oklahoma State University), Staffan Persson, and Andrew J. Mort (Oklahoma State University) is the development of a suite of cloned polysaccharide cleaving enzymes that are expressed as secreted HIS-tagged enzymes in Pichia pastoris. These enzymes allow enzymatic fingerprinting of polysaccharides by methods such as capillary electrophoresis and MALDI. A survey of the linkages cleaved by these enzymes is shown in the attached powerpoint presentation. Link to the Enzyme database.

The following photograph shows the members of my lab and Shauna Somerville's lab in the spring of 2005.

Recent publications

Lukowitz, W.L., Roeder, A., Parmenter, D., and Somerville, C.R. (2004) A MAPKK kinase gene regulates extra-embryonic cell-fate in Arabidopsis. Cell 116,109-119.

Vorwerk, S., Somerville, S.C. and Somerville, C.R. (2004) The role of plant cell wall polysaccharide composition in disease resistance. Trends Plant Sci. 9, 203-209

Bergmann, D.C., Lukowitz, W. and Somerville, C.R. (2004) A MAPKK kinase regulates cell fate in the Arabidopsis epidermis. Science 304,1494-1497

Sedbrook, J.S., Ehrhardt, D.W., Fisher, S.E., Scheible, W.R. and Somerville, C.R. (2004) The Arabidopsis SKU6/SPR1 gene encodes a plus-end localized microtubule associated protein involved in directional cell expansion. Plant Cell 16,1506-1520

McCabe, R.A., Kato, T., Lukowitz, W., Sieber, P., Tasaka, M. and Somerville, C.R. (2004) The gravitropism defective 2 (grv2) mutants of Arabidopsis are deficient in a protein implicated in endocytosis. Plant Physiol., 136, 3095-3103

Vogel, J., Raab, T., Somerville, C.R., and Somerville, S.C. (2004) Mutations in PMR5 result in powdery mildew resistance and altered cell wall composition. Plant J 40,968- 978

Assaad, F.F., Qiu, J.L., Youngs, H., Ehrhardt, D., Zimmerli, L., Kalde, M., Wanner, G., Peck, S.C., Edwards, H., Ramonell, K., Somerville, C.R., and Thordal-Christensen, H. (2004) The PEN1 syntaxin defines a novel cellular compartment upon fungal attack and is required for the timely assembly of papilla. Molec. Biol. Cell 15,5118-5129

Falcone, D.L., Ogas, J.P., and Somerville, C.R. (2005) Regulation of membrane fatty acid composition by temperature in mutants of Arabidopsis with alterations in membrane lipid composition. BMC Plant Biology 4:17

Somerville, C., Bauer, S., Brininstool, G., Facette, M., Hamann, T., Milne, J., Osborne, E., Paredez, A., Persson, S., Raab, T., Vorwerk, S., Youngs, H. (2004) Towards a systems approach to understanding plant cell walls. Science 306,2206-2211

Gillmor, C.S., Lukowitz, W., Brininstool, G., Sedbrook, J., Hamman, T., Poindexter, P. and Somerville, C.R. (2004) GPI-anchored proteins are required for cell wall synthesis and morphogenesis, but not cell proliferation, in Arabidopsis. Plant Cell 17,1128-1140.

Persson, S., Wei, H., Milne, J., Page, G.P., Somerville, C.R. (2005) Large-scale coexpression analysis reveals novel genes involved in cellulose biosynthesis. PNAS 102,8633-8638

Cutler, S., Somerville, C.R. (2005) GFP-Nit1 aggregation marks an early step of wound and herbicide induced cell death. BMC Plant Biology 5:4

Bauer, S., Vasu, P., Mort, A.J., Somerville, C.R. (2005) Cloning, expression and characterization of an oligoxyloglucan reducing end-specific xyloglucanobiohydrolase from Aspergillus nidulans. Carb. Res.,340,2590-2597.

Somerville, C.R. (2006) Cellulose synthesis in higher plants. Annu. Rev. Cell Dev. Biol. 22,53-78

Paredez, A., Somerville, C.R., Ehrhardt, D. (2006) Dynamic Visualization of Cellulose Synthase Demonstrates Functional Association with Cortical Microtubules. Science, in press