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Pamela S Mow

Botany and Plant Pathology 

  • Administrative Assistant to the Department Head
765.494.4653
765.494.0363
Lilly Hall Room 1-464

Cellulose structure and biosynthesis

With more than 200 trillion tons per year in the natural environment, cellulose is the most abundant biopolymer on Earth. Cellulose microfibrils, the fundamental scaffolding of the plant cell wall, is a para-crystalline array of several dozen (1->4)-b-D-glucan chains synthesized at the plasma membrane surface by large multicomponent complexes of cellulose synthase (CesA) proteins. We discovered that recombinant catalytic domains of CesA are two-domain structures that dimerize using Small-Angle X-ray Scattering (SAXS) experiments to derive 3-D surface contour structures (Olek et al. 2014). The catalytic domains of plant CesAs contain two unique sequences not found in prokaryotic ancestors ­– a Plant-Conserved Region (P-CR) and Class-Specific Region (CSR) of unknown function. Molecular docking experiments with the catalytic core predicted that the CSRs of CesAs are the dimerization domains. We aim to provide the first crystal structure of a plant CesA catalytic domain. Towards that goal, we crystallized a recombinant Plant-Conserved Region (P-CR) and showed that it is primarily a coiled-coil domain positioned near the entrance to the active site of the catalytic core (Rushton et al. 2016). With Wen Jiang (Purdue) we have begun studies to define the assembly of CesAs into complexes at the Golgi membrane as part of a broader effort to characterize the dynamics of the Golgi proteome.  From substrate binding stoichiometry, we know that each CesA protein synthesizes a single (1->4)-b-D-glucan chain of a microfibril (Olek et al. 2014). We developed a modified TEMPO-catalyzed oxidation of glucose to uronosyl residues followed by carboxyl reduced with NaBD4 to provide a novel method for determining proportion of disordered surfaced chains, ordered surface chains in which only one-half of the residues are exposed to water, and completely anhydrous core-crystalline residues for cellulose microfibrils in biomass. Microfibrils of primary or secondary walls from seedlings and lignocellulosic biomass have significantly higher content of their glucan chains in anhydrous domains, indicating cellulose microfibrils into bundles with extensive crystalline continuity.

 

Cell-wall gene discovery

For several decades, my lab focused on determining the fine structure and dynamics of synthesis and degradation of the non-cellulosic polysaccharides of the plant cell wall. This work established that flowering plants synthesize two distinct kinds of primary cell walls – a ‘Type I’ wall made by most dicots and about one-half of monocots, and a ‘Type II’ wall made by grasses and closely related ‘commelinid’ monocots (Carpita and Gibeaut, 1993). This work has had a major impact on fashioning perspectives for how the unique chemical structure of grasses impacts technologies for their conversion to biofuels and bio-based products. Our discovery of unique arabinoxylan and rhamnogalacturonan I structures in seed mucilages not seen in growing cell walls supports a hypothesis that plants make a selected few ubiquitous backbone polymers onto which a broad spectrum of side group substitutions are added to engender many possible functions. We have annotated almost 1500 genes that function in wall biogenesis in Arabidopsis, rice, and maize, a model C4 grass, assembling them into 74 gene families (Penning et al. 2009). We continue to expand annotations of the many gene families of cell-wall related g

Awards & Honors

(2014) Team Award. College of Agriculture.

Selected Publications

Rushton, P. S., Olek, A. T., Makowski, L., Badger, J., Steussy, C. N., Carpita, N. C., & Stauffacher, C. V. (2016). Rice Cellulose SynthaseA8 Plant-Conserved Region Is a Coiled-Coil at the Catalytic Core Entrance. Manuscript in preparation.

Dugard, C. K., Mertz, R. A., Rayon, C., Mercadante, D., Hart, C., Benatti, M. R., . . . Carpita, N. C. (2016). The Cell Wall Arabinose-Deficient Arabidopsis thaliana Mutant murus5 Encodes a Defective Allele of REVERSIBLY GLYCOSYLATED POLYPEPTIDE2. Plant Physiology, 171(3), 1905-20. doi:10.1104/pp.15.01922

McCann, M. C., & Carpita, N. C. (2015). Biomass recalcitrance: a multi-scale, multi-factor, and conversion-specific property. Journal of Experimental Botany, 66(14), 4109-18. doi:10.1093/jxb/erv267

Penning, B. W., Sykes, R. W., Babcock, N. C., Dugard, C. K., Held, M. A., Klimek, J. F., . . . Carpita, N. C. (2014). Genetic Determinants for Enzymatic Digestion of Lignocellulosic Biomass Are Independent of Those for Lignin Abundance in a Maize Recombinant Inbred Population. Plant Physiology, 165(4), 1475-1487. doi:10.1104/pp.114.242446

Olek, A. T., Rayon, C. J., Makowski, L., Kim, H., Ciesielski, P., Badger, J., . . . Carpita, N. C. (2013). Small-angle x-ray scattering reveals the structure of the catalytic domain of a cellulose synthase and its assembly into dimers. Plant Cell, 26, 2966-3009. doi:10.1105/tpc.114.126862

Rayon, C., Olek, A. T., & Carpita, N. C. (2013). Towards redesigning cellulose biosynthesis for improved bioenergy feedstocks. In Plants and Bioenergy (183-193). New York, NY: Springer. doi:10.1007/978-1-4614-9329-7_11

Held, M. A., Penning, B., Brandt, A. S., Kessans, S. A., Yong, W., Scofield, S. R., & Carpita, N. C. (2008). Small-interfering RNAs from natural antisense transcripts derived from a cellulose synthase gene modulate cell wall biosynthesis in barley. Proceedings of the National Academy of Sciences of the United States of America, 105(51), 20534-9. doi:10.1073/pnas.0809408105

Naran, R., Chen, G., & Carpita, N. C. (2008). Novel rhamnogalacturonan I and arabinoxylan polysaccharides of flax seed mucilage. Plant Physiology, 148(1), 132-41. doi:10.1104/pp.108.123513

Urbanowicz, B. R., Rayon, C., & Carpita, N. C. (2004). Topology of the maize mixed linkage (1->3),(1->4)-beta-d-glucan synthase at the Golgi membrane. Plant Physiology, 134(2), 758-68. doi:10.1104/pp.103.032011

Vergara, C. E., & Carpita, N. C. (2001). Beta-D-glycan synthases and the CesA gene family: lessons to be learned from the mixed-linkage (1-->3),(1-->4)beta-D-glucan synthase. Plant Molecular Biology, 47(1-2), 145-60.