Viktor Kirik

Phone: (309) 438 - 2608
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Research

Spatially oriented cell divisions play an important role in cell differentiation, stem cells maintenance and they are critical during organ and tissues formation. How cells define their division plane is a fundamental question in cell and developmental biology. Both animal and plant cells use elaborate mechanisms that control division plane selection. While the mechanisms that determine cell division sites are poorly understood, involvement of microtubule (MT) cytoskeleton has emerged as a common theme.

Alpha/beta-tubulin heterodimers are building blocks of MT protofilaments closed into a hollow tube. MT are intrinsically polar structures with beta-tubulin pointing towards a dynamic plus-end microtubule and alpha-tubulin towards a more stable minus end (see Movie 1).

Our previous data showed the important role of the MT cytoskeleton in cell division and morphogenesis in plants (Kirik et al., 2002a; 2002b; 2007). MTs in plant cells form four distinct MT arrays: interphase cortical array, the preprophase band (PPB), spindle, and phragmoplast. Formation and disassembly of MT arrays are regulated by microtubule associated proteins (MAPs) which bind to MTs and regulate MT dynamic properties and interactions.

 
Movie 1. GFP-labelled cortical microtubules of plant epidermal cells display highly dynamic behavior. Growing MT plus ends are labelled with EB1:mCherry fusion protein.
 
Movie 2. Preprophase band in a dividing plant epidermal cell.
GFP-labelled MTs form a ring or, more precisely, a polygon at the equatorial cell cortex. The Movie is a 3D reconstruction of confocal sections through a plant cell entering mitosis.

 

Our current research is focused on the regulatory mechanisms which organize cortical MTs into intephase and PPB arrays. PPB microtubules form a ring around the equator of a premitotic cell (Movie 2). The position of the PPB faithfully predicts the future plane of cell division and it has a key role in determination of the cell division plane (for review see Smith, 2001). What determines the position of the PPB at the onset of cell division and how the PPB is formed are key questions that have to be answered to understand the mechanism of division plane determination in plants.

We are using a combination of genetic, molecular and cell biological methods to address the role of the MT cytoskleleton in division plane determination and cell morphogenesis.

Kirik V, Mathur J, Grini PE, Klinkhammer I, Adler K, Bechtold N, Herzog M, Bonneville JM, Huelskamp M. (2002a). Functional analysis of the tubulin-folding cofactor C in Arabidopsis thaliana. Curr Biol. 12(17), 1519-23.
Kirik V, Grini PE, Mathur J, Klinkhammer I, Adler K, Bechtold N, Herzog M, Bonneville JM, Huelskamp M. (2002b). The Arabidopsis TUBULIN-FOLDING COFACTOR A gene is involved in the control of the alpha/beta-tubulin monomer balance. Plant Cell 14(9), 2265-2276.
Kirik V, Herrmann U, Parupalli C, Sedbrook J. C, Ehrhardt D. W. and Hulskamp M. (2007). CLASP localizes in two discrete patterns on cortical microtubules and is required for cell morphogenesis and cell division in Arabidopsis. Journal of Cell Science 120, 4416-4425.
Smith, L. G. (2001). Plant cell division: building walls in the right places. Nat Rev Mol Cell Biol 2, 33-39.