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Accueil du site > Animations Scientifiques > Séminaires 2008 > The mechanics behind plant development : a pluridisciplinary view

The mechanics behind plant development : a pluridisciplinary view

par Webmaster - 6 février 2008

Orateur :

Jan Traas, Laboratoire de Reproduction et Développement des Plantes, ENS-Lyon

Salle :

C023 (RDC LR6 côté CECAM)

Sujet :

We are studying the role of physical forces during plant development. Pioneering work on plants, in particular by Green and colleagues, has suggested that physical stress created by differential tissue expansion patterns is interpreted by the cells in terms of particular growth characteristics and patterns of differentiation. So far, however, it has been impossible to go beyond the general idea that physical forces are important in morphogenesis, and their precise effects on processes such as cell expansion and cell differentiation are unknown. We are currently re-examining this issue exploiting new imaging technologies combined with genetics, micro-mechanical approaches and mathematical modelling. Hereby we are focusing on the shoot apical meristem in higher plants. This is a population of stem cells which continuously initiates aerial organs and, therefore, is a basic determinant of plant architecture. The link between mechanical constraints and a major structural cellular component, the cytoskeleton, receives particular attention. We have analysed the behaviour of an important cytoskeletal filamentous network, the microtubules. This has revealed the presence of highly dynamic but stereotypic microtubule orientations in the meristem. The microtubule arrays are aligned to predicted stress patterns at the meristem surface and react to externally applied constraints in a cell autonomous way. We show, using mathematical modeling, that a cell autonomous reaction to stress patterns would be sufficient to generate the observed behaviour of microtubules.

Interestingly, when microtubules are depolymerized using drug treatments, the cells loose their capacity to grow anisotropically. As a result, the meristematic cells adopt a number of growth properties usually observed in foams and the tissue is no longer able to carry out certain morphogenetic processes such as tissue folding.

We therefore propose that microtubules, by resisting to the physical stress vectors that arise during anisotropic growth, allow specific events such as directional organ outgrowth and tissue folding.

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