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. The Preprophase Band (PPB) in a dividing plant epidermal cell. mCherry-labelled microtubules 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. Microtubules are shown in the red color; yellow color shows accumulation of the CLASP microtubule-associated protein.

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.