Plant cell biology, cellular basis of secretion of plant cell wall components; lignification in xylem development; ABC transporters and cuticle secretion
B.Sc. (1984), McGill Univ.;
Ph.D. Botany (1989) UBC;
Postdoctoral Fellow, (1993-95), Univ. Colorado;
Research Associate, (1996-2000) UBC
The Samuels lab studies how plant cells secrete their cell walls, both the polysaccharides and specialized cell wall components such as lipids and lignin. Our approach is to integrate cell biology with molecular biology and biochemistry to put cell wall biosynthesis and secretion into a cellular context. All plant growth, including agricultural and forestry production, is based on the organized assembly of plant cells into tissues, organs and whole plants. The plant cell wall determines the shape of the cell and connects cells into tissues and higher order structures, thus plant growth depends on cell wall production. In addition, terrestrial plants have evolved specialized regions of cell walls, such as the plant cuticle and lignified cell walls that are essential for water retention and water conduction, respectively. Lignified cell walls, such as those found in vascular tissues like wood, make the wall strong and waterproof. The removal of lignin from the cellulose of the cell wall has been identified as a barrier to enzymatic degradation of cellulose feedstock for biofuels, so there is strong interest in understanding lignified secondary cell walls.
1. Xylem development and lignification
Wood fibers are the cellular basis of paper, cotton, building products, as well as having potential for the production of cellulosic biofuels. We study the cellular events underlying wood formation. Using cryo-fixation methods and transmission electron microscopy, we can follow xylem development from birth in the vascular cambium (Rensing et al., 2002, Trees-Struc&Func), through secondary cell wall secretion (Kaneda et al., 2010, J. Int Plant Biol.) to lignification (Kaneda et al., 2008, Plant Phys) and programmed cell death (Courtois-Moreau et al., 2009, Plant J). One of the biggest challenges in this field is elucidating how lignin precursors, the monolignols, are exported. Lignin precursors, monolignols, in developing xylem during lignification can be tracked using cryofixation/autoradiography. Using inhibitors of protein translation and phenylpropanoid metabolism, we demonstrated that monolignols do not appear in the Golgi secretory pathway, which was the current model, suggesting that unknown transporters must be exporting lignin precursors from the cell (Kaneda et al 2008 Plant Physiol).
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 cryo-fixation and autoradiography to study the distribution of phenylpropanoids in these cells (Kaneda et al.,2008, Plant Physiol).
2. ABC transporters and cuticular lipid export in Arabidopsis
The exterior of a plant has a specialized cell wall that is coated with protective lipids (the cuticle). These lipids are synthesized in epidermal cells and ATP binding cassette (ABC) transporters are required for the export of lipids to the plant surface. The ABCG transporters are monomers encoded as two separate genes and they must dimerize with a partner to form a functional transporter. Based on mutant phenotypes of abcg mutants in Arabidopsis, we hypothesized that ABCG11 and ABCG12 form diverse partnerships which could provide a mechanism for transport of different cuticle components (Bird et al., 2007 Plant J). This hypothesis has been supported by protein-protein interaction and intracellular trafficking data (McFarlane et al., 2010 Plant Cell). The role of ABC transporters in cuticular lipid traffic in epidermal cells is a specific system but it is likely that ABC transporters also play additional roles in lipid traffic in plant cells. Once wax molecules are exported, they must enter the hydrophilic environment of the cell wall and mutant analyses have demonstrated that a GPI-anchored lipid transfer protein at the plasma membrane is required for wax export (DeBono et al., 2010, Plant Cell).
cryoSEM of wax on the surface of an Arabidopsis stem.
BIOL 535 - Teaching and Learning in the Life Sciences
Quilichini, T.D., Samuels, A.L., and Douglas, C.J. ABCG26-Mediated Polyketide Trafficking and Hydroxycinnamoyl Spermidines Contribute to Pollen Wall Exine Formation in Arabidopsis. Plant Cell doi: http://dx.doi.org/10.1105/tpc.114.130484 The Plant Cell November 2014 tpc.114.13048
Schuetz, M., Benske, A., Smith, R.E., Watanabe, Y., Tobimatsu, Y., Ralph, J., Demura, T., Ellis, B., Samuels, A.L. (2014) Laccases direct lignification in the discrete secondary cell wall domains of protoxylem. Plant Physiology. First Published on August 25, 2014; doi: http://dx.doi.org/10.1104/pp.114.245597
McFarlane, H.E., Watanabe, Y., Yang, W., Huang, Y., Ohlrogge, J., and Samuels, A.L. (2014) Golgi- and Trans-Golgi Network-Mediated Vesicle Trafficking Is Required for Wax Secretion from Epidermis. Plant Physiology 164: 1250-1260.
Quilichini T.D., Douglas C.J., and Samuels A.L. (2014) New views of tapetum ultrastructure and pollen exine development in Arabidopsis thaliana. Annals of Botany, doi: 10.1093/aob/mcu042
Smith, R.A., Schuetz, M., Roach, M., Mansfield, S.D., Ellis B.E., Samuels, L. (2013) Neighboring parenchyma cells can contribute to Arabidopsis xylem lignification, while lignification of interfascicular fibers is cell autonomous. Plant Cell 25: 3988-99.
McFarlane, H.E., Watanabe, Y., Carruthers, K., Lesvesque-Tremblay, G., Haughn, G.W., Gendre, D., Bhalerao, R.P., Samuels, A.L. (2013) The echidna mutant demonstrates that pectic polysaccharides and proteins require distinct post-Golgi vesicle traffic machinery. Plant & Cell Physiology 54: 1867-1880.
Boutté, Y., Jonsson, K., McFarlane, H.E., Johnson, E., Gendre, D., Swarup, R., Friml, J., Samuels, L., Robert, S., Bhalerao, R. (2013) ECHIDNA-mediated Secretory Trafficking of Auxin Carriers for Differential Cell Elongation in Arabidopsis Proceedings of the National Academy of Sciences USA, 110:16259-64.
Gendre D., Oh J., Boutté Y., Best J.G., Samuels L., Nilsson R., Uemura T., Marchant A., Bennett M.J., Grebe M. & Bhalerao R.P. (2011) Conserved Arabidopsis ECHIDNA protein mediates trans–Golgi-network trafficking and cell elongation. Proceedings of the National Academy of Sciences 108: 8048-8053.
Kaneda, M. Schuetz, B.S.P. Lin, C. Chanis, B. Hamberger, T.L. Western, J. Ehlting, A.L. Samuels (2011) ABC transporters coordinately expressed during lignification of Arabidopsis stems include a set of ABCB's associated with auxin transport. Journal of Experimental Botany 62: 2063-2077.
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. [view full text]
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