- Ph.D., University of California, Irvine, 1986
- M.A., San Francisco State University, 1982
- B.A., University of California, Berkeley, 1978
The Plant Cytoskeleton in Growth and Development
In the broadest sense, the Cyr lab is interested in knowing how cellular processes affect plant morphogenesis and plant physiology. Our investigations currently center on the behavior of the plant cytoskeleton and, in particular, on the microtubules involved in cell elongation and cell division.
What are the mechanisms that ensure that cell division occurs in the proper manner? Plant cells are literally stuck to one another throughout life; therefore, the orientation of the cell division plane plays a significant role in morphogenesis. A pre-prophase band (PPB) of microtubules is involved in this process, but at the molecular level little is known about how it carries out its function. Our current studies make extensive use of genetic fusions between several Intrinsically Fluorescent Proteins (IFPs) and various cytoskeletal genes (including tubulin, kinesins, EB-1, and nuclear envelope proteins). We routinely produce transgenic plants and cell lines that stably express these synthetic genes in order to follow the cellular dynamics of their products, using vital imaging with confocal microscopy and wide-field light microscopic techniques. The ability to simultaneously follow multiple gene products in a single cell has opened up new opportunities for learning about the interactions of cytoskeletal proteins in growing and dividing cells.
The cortical microtubule arrays of plant cells become highly organized as cells elongate, but the nature of this organization is unknown. We recently have discovered that the stochastic parameters that describe the dynamicity of this array are deterministically modified by intermicrotubule encounters. Using Monte-Carlo modeling, we have found that these two deterministic parameters were sufficient to affect the local ordering in a simulated population of random microtubules. Our goal is to identify the organizational rules that promote regional and global ordering of this array.
We currently are investigating a number of molecular motors (i.e. kinesins) that affect cell division. In these studies, we employ biochemical techniques to understand the biophysics of these motors. Various gene truncates have been produced to better understand the structure/function relationships between various kinesin family members. The ability to combine techniques from the disciplines of cell biology, genetics, computer science, and biochemistry will continue to allow us to answer the more fundamental questions about the plant cytokskeleton.
Ambrose, J. C. and R. Cyr. 2008. Mitotic spindle organization by the preprophase band. Mol. Plant 1: 950-960.
Quan, L., R. Xiao, W. Li, H. Kong, J. C. Ambrose, J. L. Malcos, R. Cyr, D. Twell, and H. Ma. 2008. Functional divergence of the duplicated AtKIN14b and AtKIN14b genes: critical roles in Arabidopsis meiosis and gametophyte development. Plant J. 53: 1013-26.
Ambrose, J. C. and R. J. Cyr. 2007. The kinesin ATK5 functions in early spindle assembly in Arabidopsis. Plant Cell 19: 226-236.
Dixit, R., E. Chen, and R. J. Cyr. 2006. Establishment of polarity during organization of the acentrosomal plant cortical microtubule array. Mol. Biol. Cell. 17: 1298-305.
Marcus, A., R. Dixit, and R. J. Cyr. 2005. Narrowing of the pre-prophase microtubule band development is not required for cell division plane determination in plants. Protoplasma 226: 169-174.
Ambrose, J. C., W. Li, A. Marcus, H. Ma, and R. J. Cyr. 2005. A minus-end directed kinesin with +TIP activity is involved in spindle morphogenesis. Mol. Biol. Cell 16: 1584-1592.
Patel, S., A. Rose, T. Meulia, R. Dixit, R. Cyr, and I. Meier. 2004. Arabidopsis WPP-Domain proteins are developmentally associated with the nuclear envelope and promote cell division. Plant Cell 16: 3260-3273.
Dixit, R. and R. J. Cyr. 2004. Encounters between dynamic cortical microtubules promote ordering of the cortical array through angle-dependent modifications of microtubule behavior. Plant Cell 16: 3274-3284.
Dixit, R. and R. J. Cyr. 2003.Cell damage and reactive oxygen species induced by fluorescence microscopy: Effect on mitosis and guidelines for non-invasive fluorescence microscopy. Plant J. 36: 280-290.