Associate Professor of Biology, University of Massachusetts
Ph.D.: Stanford University
Regulation of Plant Morphogenesis During Growth & Development
Plant forms have long delighted artists and naturalists with their variety and beauty. These forms arise through morphogenesis in a process that depends on growth. Cells specify their growth rates in each spatial dimension and these rates are usually different from one another, that is, the growth of plant cells is anisotropic. To build an organ with a defined shape, the plant must control precisely the direction of maximal expansion and the magnitude of expansion anisotropy. Understanding the mechanisms whereby plant cells govern growth anisotropy is the crux of my research.
To unearth these mechanisms I am digging in three types of terrain. The first is to understand how cell division and expansion are regulated coordinately. Cell division supplies the plant with building blocks whereas cell expansion determines the shape of the blocks and hence of the whole structure. These processes must be coordinated precisely for morphogenesis to succeed, but those interested in division have typically ignored expansion, and vice versa . My laboratory is quantifying the spatial profiles of cell expansion and division at high spatio-temporal resolution and studying how these change in different environments or in different genetic backgrounds. As part of this effort, I collaborated with a computer scientist to develop a novel image processing routine allowing growth profiles to be measured algorithmically.
The second terrain is the role of the cytoskeleton in regulating anisotropic expansion. For years, the cytoskeleton has been known to be important for morphogenesis by virtue of the aberrant morphology that results when the cytoskeleton is disrupted by chemical inhibitors. But how does the cytoskeleton act? This question requires more than inhibitors to answer. My laboratory has isolated mutants of arabidopsis in which root morphology is aberrant and we are using those to identify proteins that make up the pathway for the control of organ shape. Additionally, we have designed a novel in vitro assay specifically for cortical microtubules, where there behavior can be studied readily and the function of putative players tested directly.
The third terrain is the cell wall, the ultimate regulator of cell and organ shape. Cells can expand anisotropically only when the cell wall is mechanically anisotropic. The mechanical anisotropy is provided by cellulose microfibrils, long polymers of glucose crystallized into microfibrils with the tensile strength of steel; however, it is not known how cellulose alignment is controlled. In addition to the mutational approach mentioned above, my laboratory uses several approaches to study the ultrastructure of the cell wall, including quantitative polarized-light microscopy, field-emission scanning electron microscopy, and atomic force microscopy. The overall goal here is to uncover how anisotropic wall yielding is conditioned by the structural elements of the cell wall.
Baskin, T.I. , Cork, A., Williamson, R.E., Gorst, J.R. 1995. STUNTED PLANT 1 , a gene required for expansion in rapidly elongating but not in dividing cells, and mediating root growth responses to applied cytokinin. Plant Physiology 107: 233-243.
Baskin, T.I. , Bivens, N.J. 1995. Stimulation of radial expansion in arabidopsis roots by inhibitors of actomyosin and vesicle secretion but not by various inhibitors of metabolism. Planta 197: 514-521.
Liang, B.M., Dennings, A.M., Sharp, R.E., Baskin, T.I. 1996. Consistent handedness of micro-tubule helical arrays in maize and arabidopsis primary roots. Protoplasma 190: 8-15.
Baskin, T.I. , Miller, D.D., Vos, J.W., Wilson, J.E., Hepler, P.K. 1996. Cryofixing single cells and multicellular specimens enhances structure and immunocytochemistry for light microscopy. Journal of Microscopy 182: 149-161.
Baskin, T.I., Wilson, J.E. 1997. Inhibitors of protein kinases and phosphatases alter root morphology and disorganize cortical microtubules. Plant Physiology 113: 493-502.
Liang, B.M., Sharp, R.E., Baskin, T.I. 1997. Regulation of growth anisotropy in well watered and water-stressed maize roots I. Spatial distribution of longitudinal, radial and tangential expansion rates. Plant Physiology 115: 101-111.
Assmann, S.M., Baskin, T.I. 1998. The function of guard cells does not require an intact array of cortical microtubules. Journal of Experimental Botany , 49: 163-170.
Beemster, G.T.S., Baskin, T.I. 1998. Analysis of cell division and elongation underlying the developmental acceleration of root growth in Arabidopsis thaliana . Plant Physiology , 116: 1515-1526.
Baskin, T.I. , Meekes, H.T.H.M., Liang, B.M., Sharp, R.E. 1999. Regulation of growth anisotropy in well watered and water-stressed maize roots. II. Role of cortical microtubules and cellulose microfibrils. Plant Physiology , 119: 681-692.
Baskin, T.I. 2000. On the constancy of cell division rate in the root meristem. Plant Molecular Biology , 43: 545-554.
van der Weele, C.M., Spollen, W.G., Sharp, R.E., Baskin, T.I. 2000. Growth of Arabidopsis thaliana seedlings under water deficit studied by control of water potential in nutrient-agar media. Journal of Experimental Botany , 51: 1555-1562.
Beemster, G.T.S., Baskin, T.I. 2000. STUNTED PLANT 1 mediates effects of cytokinin, but not of auxin, on cell division and expansion in the root of Arabidopsis thaliana . Plant Physiology , 124: 1718 - 1727.
Baskin, T.I. 2001. On the alignment of cellulose microfibrils by cortical microtubules: A review and a model. Protoplasma , 215: 150-171.
Schindelman, G., Morikami, A., Jung, J., Baskin, T.I. , Carpita, N.C., Derbyshire, P., McCann, M.C., Benfey, P.N. 2001. COBRA encodes a putative GPI-anchored protein, which is polarly localized and necessary for oriented cell expansion in Arabidopsis . Genes and Development , 15: 1115-1127.
Lane, D.R., Wiedemeier, A., Peng, L., Höfte, H., Hocart, C.H., Birch, R.J., Baskin, T.I. , Burn, J.E., Arioli, T., Betzner, A.S., Williamson, R.E. 2001. Temperature-sensitive alleles of radially swollen2 link the KORRIGAN endo-1,4-ß-glucanase to cellulose synthesis and cytokinesis. Plant Physiology , 126: 278-288.
Wiedemeier, A.M.D., Judy-March, J.E., Hocart, C.H., Wasteneys, G.O., Williamson, R.E., Baskin, T.I. 2002. Mutant alleles of arabidopsis RADIALLY SWOLLEN 4 and RSW7 reduce growth anisotropy without altering the transverse orientation of cortical microtubules or cellulose microfibrils. Development , 129: 4821-4830.
Andème-Onzighi, C., Sivaguru, M., Judy-March, J., Baskin, T.I. , Driouich, A. 2002. The reb1-1 mutation of Arabidopsis alters the morphology of trichoblasts, the expression of arabinogalactan-proteins and the organization of cortical microtubules. Planta , 215: 949-958.
Ma, Z., Baskin, T.I. , Brown, K.M., Lynch, J.P. 2003. Regulation of root elongation under phosphorus stress involves changes in ethylene responsiveness. Plant Physiology , 131: 1381-1390.
van der Weele, C.M., Jiang, H., Palaniappan, K.K., Ivanov, V.B., Palaniappan, K., Baskin, T.I. 2003. A new algorithm for computational image analysis of deformable motion at high spatial and temporal resolution applied to root growth: Roughly uniform elongation in the meristem and also, after an abrupt acceleration, in the elongation zone. Plant Physiology , 132: 1138-1148.
Sivaguru, M., Pike, S., Gassmann, W., Baskin, T.I. 2003. Aluminum rapidly depolymerizes cortical microtubules and depolarizes the plasma membrane: Evidence that these responses are mediated by a glutamate receptor. Plant and Cell Physiology , 44: 667-675.
Tian, G.W., Smith, D., Glück, S., Baskin, T.I. 2004. The higher plant cortical microtubule array analyzed in vitro in the presence of the cell wall. Cell Motility and the Cytoskeleton , 57: 26-36.
Palaniappan, K., Jiang, H., Baskin, T.I. 2004. Non-rigid motion estimation using the robust tensor method", In: IEEE Computer Vision & Pattern Recognition Workshop on Articulated and Nonrigid Motion, , Washington, DC, IEEE Computer Society, pp. 25-33.
Baskin, T.I. , Beemster, G.T.S., Judy-March, J.E., Marga, F. 2004. Disorganization of cortical microtubules stimulates tangential expansion and reduces the uniformity of cellulose microfibril alignment among cells in the root of Arabidopsis thaliana. Plant Physiology , 135: 2279-2290.
Marga, F., Grandbois, M., Cosgrove, D.J., Baskin, T.I. 2005. Cell wall extension results in the coordinate separation of parallel microfibrils: Evidence from scanning electron microscopy and atomic force microscopy. Plant Journal , 43: 181-190.
Baskin, T.I. 2005. Anisotropic expansion of the plant cell wall. Annual Review of Cell and Developmental Biology 21: 203-222.
Murata, T., Sonobe, S., Baskin, T.I. , Hyodo, S., Hasezawa, S., Nagata, T., Horio, T., Hasebe, M. 2005. Microtubule-dependent microtubule nucleation based on recruitment of g-tubulin in higher plants. Nature Cell Biology , 7: 961-968.