Poster: Late and Moved Abstracts
Abs #
960: The arabidopsis mor1 (microtubule organization 1) mutant shows increased sensitivity to microfilament disruption.
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Presenter: |
Collings, David , collings@rsbs.anu.edu.au |
Authors | Collings, David (A) Lill, Adrian (A) Kawamura, Eiko (A) (B) Himmelspach, Regina (A) Wasteneys, Geoff (A) (B) | | Affiliations: |
(A): Australian National University
(B): University of British Columbia
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The MOR1 gene of Arabidopsis thaliana encodes a 217 kDa microtubule-binding protein that is a DIS1-TOGp-XMAP215 homologue. A mutant, mor1-1, has a single point mutation in an N-terminal HEAT repeat potentially involved in protein-protein interactions. This mutant grows normally at 21oC but at 29oC, suffers from disorganised microtubules and a loss of growth anisotropy that leads to reduced cell and root elongation, and root swelling (Whittington et al., 2001 [Nature 411: 610-613]). The mor1 mutant also exhibits irregular cell divisions, especially after 24 or more hours at high temperatures, with mis-oriented spindles and unusual phragmoplasts that generate irregular cross-walls. We have compared the sensitivity of mor1 and wild-type plants to the microtubule-depolymerising drug oryzalin, and the microtubule-stabilising drugs taxol. In mor1 plants grown at the restrictive temperature, both oryzalin and taxol cause root swelling at significantly lower concentrations than required for wild-type plants, or mor1 plants at the permissive temperature. Disruption of the microfilament cytoskeleton with the actin-disrupting drugs latrunculin B and cytochalasin D also cause irregular cell divisions, reduced cell and root elongation, and root swelling. Further, in mor1 plants grown at the restrictive temperature, sensitisation to these drugs also occurs, with root swelling occurring at significantly lower latrunculin and cytochalasin concentrations. This sensitisation of the actin microfilament cytoskeleton by microtubule disruption suggests that some form of interaction occurs between the microtubules and microfilaments during cell elongation and the control of anisotropic growth in arabidopsis roots.
