Poster: Cell Walls

Abs # 1274: The cell wall in the microtubule organization mutant mor1-1

Presenter:	Himmelspach, Regina , himmelspach@rsbs.anu.edu.au
Authors	Himmelspach, Regina  (A)   Williamson, Richard E (A)   Collings, David  (A)   Wasteneys, Geoffrey O (A)
Affiliations:	(A): Research School of Biological Sciences, The Australian National University

The mor1-1 mutant of Arabidopsis thaliana has a single amino acid substitution in a 217 kDa microtubule-binding protein, which generates a temperature-sensitive phenotype. At the permissive temperature, 21°C, the mutant plants grow normally, but at 30°C cortical microtubule arrays become disorganized, cells and organs swell, and growth anisotropy is lost. The cell wall is the major load-bearing component of a plant cell. Composition and architecture of the cell wall determine the direction in which a growing cell can expand. Since cells lose the ability to elongate anisotropically after microtubule disruption in mor1-1, we assume that changes in the cell wall must also occur. We show that the production and alignment of cellulose, the major structural polysaccharide of higher plant cell walls, is not affected in mor1-1. Secondary wall thickenings also form properly in mor1-1 inflorescence stems. We are currently testing changes in cell wall composition in mor1-1 at the restrictive temperature with immunocytochemistry. Most interestingly we observe incomplete cell walls, mis-oriented spindles, and unusual phragmoplasts in mor1-1 roots at 30°C. This indicates that the mutation in the microtubule-binding protein might prevent normal cell plate alignment during cell division.