Research Interests:

My area of interest is plant cell biology, especially the biosynthesis and secretion of the plant cell wall.

The study of the extracellular matrix in plants presents special challenges for cell biologists due to the tight association of the wall with the plasma membrane and the plants' turgor-driven mode of growth. The cell wall limits the reagents and probes that can be applied to the plant cell and removal of the cell wall requires altering the normal osmotic environment of the cell. For these reasons, I use specialized freezing techniques (cryofixation) such as high pressure freezing, which can immobilize cell water intact and allow detailed electron microscopic examination of the cell.

1. Cytokinesis

In the past, I have studied how dividing plant cells produce the new cell wall following mitosis. Using cryofixation, as well as antibody probes, a new view of the developing cell plate was elucidated in tobacco cells grown in culture. More recently, we have studied this process in the inner bark (secondary vascular cambium) of pine and found the same delicate membrane structures as in tobacco.

TEM of High pressure frozen/Freeze substituted Pine cambium showing new cell wall forming (cell plate).

Rensing et al. (2002).

2. Xylem development and lignification

Recently my research interests have expanded to focus on non-polysaccharide components of the cell wall such as lignin and wax. Lignin is a polymer made up of units called monolignols, which link together to give plant cell walls strength. The monolignols must be exported from the cytoplasm to specific sites in the cell wall. Using developing secondary xylem (wood) of Pinus contorta var. latifolia (Lodgepole Pine) as an experimental system, We are exploring how some of the enzymes of monolignol biosynthesis are arranged in the cell and what is the cellular mechanism of monolignol export.

Typical cell structures observed in developing xylem from Pinus contorta var. latifolia. Cells were prepared by cryofixation and TEM. Both membrane and cytoskeleton structures are preserved in these cells which are actively secreting the thick secondary cell wall.

Unusual Golgi structures are characteristic of differentiating Pinus secondary xylem (wood). Cells were prepared by cryofixation and TEM. We are presently using cryo-fixation and autoradiography to study the distribution of phenylpropanoids in these cells.

3. Epicuticular wax secretion in Arabidopsis

cryoSEM of wax on the surface of an Arabidopsis stem.

Wax is an essential feature of aerial portions of plants, as it limits water loss and protects from environmental and insect stresses. The epidermal cells of the stem synthesize and secrete this hydrophobic product. It is not known if secretion is Golgi-mediated or how the hydrophobic product is targeted to the extracellular environment. In Arabidopsis thaliana, mutants have been identified which are impaired in stem wax productions. Studying these mutants using a combination of cryofixation/electron microscopy, light microscopy, gas chromatography, and freeze fracture, is giving us new insights on the mechanism of wax secretion.

McFarlane, H.E., Shin, J.J., Bird, D.A., and Samuels, A.L. 2010. Arabidopsis ABCG transporters, which are required for export of diverse cuticular lipids, dimerize in different combinations. Plant Cell 22: 3066-3075. [view abstract]

Quilichini, T.D., Friedmann, M.C., Samuels, A.L., and Douglas, C.J. 2010. ATP-binding cassette transporter G26 (ABCG26) is required for male fertility and pollen exine formation in Arabidopsis. Plant Physiology 154: 678-690. [view abstract]

Kaneda, M., Rensing, K., and Samuels, A.L. 2010. Secondary cell wall deposition in developing secondary xylem of poplar. Journal of Integrative Plant Biology 52: 234-243. [view abstract]

Kunst, L. and Samuels, A.L. 2009. Plant cuticles shine: advances in wax biosynthesis and export. Current Opinion in Plant Biology 12: 721-727. [view abstract]

DeBono, A., Yeats, T.H., Rose, J.K.C., Bird, D., Jetter, R., Kunst, L., and Samuels, A.L. 2009. Arabidopsis LTPG is a glycosylphosphatidylinositol-anchored lipid transfer protein required for export of lipids to the plant surface. The Plant Cell 21: 1230-1238. [view abstract] [Faculty of 1000]

M. Kaneda, K.H. Rensing, J.C.T. Wong, B. Banno, S.D. Mansfield, A.L. Samuels. (2008) Tracking Monolignols During Wood Development in Pinus contorta var. latifolia. Plant Physiology First published on June 11, 2008; 10.1104/pp.108.121533.

Robin E. Young, Heather E. McFarlane, Michael G. Hahn, Tamara L. Western, George W. Haughn, A. Lacey Samuels. (2008) Analysis of the Golgi apparatus in Arabidopsis seed coat cells during polarized secretion of pectin-rich mucilage. Plant Cell, First published on June 3, 2008; 10.1105/tpc.108.058842. http://www.plantcell.org/cgi/content/short/tpc.108.058842?keytype=ref&ijkey=Ox7pzryqDr1MRXN

P.J. Verrier, D. Bird, B. Burla, E. Dassa, C. Forestier, M. Geisler, M. Klein, Ü. Kolukisaoglu, Y. Lee, E. Martinoia, A. Murphy, P.A. Rea, L. Samuels, B. Schulz, E.J. Spalding, K. Yazaki and F.L. Theodoulou (2008) Plant ABC proteins – a unified nomenclature and updated inventory. Trends in Plant Science 13: 151-159.

Samuels A.L., L. Kunst, R. Jetter (2008) Sealing plant surfaces: cuticular wax formation by epidermal cells. Annual Review of Plant Biology. Vol. 59: 683-70.
http://arjournals.annualreviews.org/eprint/85MD3UMSPqz2nNXcFuaR/full/10.1146/annurev.arplant.59.103006.093219
This Annual Review is linked to a video starring Botany grad students, Allan DeBono, Patricia Lam and Miao Wen, describing the use of Arabidopsis mutants to study the plant cuticle. JOVE video