|講演者||Olivier Hamant 博士|
|タイトル||Mechano-Devo: Mechanical signals in plant development|
Studies in animal single cells have shown that mechanical cues can affect important cell processes such as cell polarity, cell fate or cell division. Here we take advantage of the simpler plant mechanics to investigate this question in a tissue context. Using confocal live imaging, micromechanics and modeling, we found that mechanical signals control the orientation of cortical microtubules, which guide the deposition of cellulose and thus control the mechanical anisotropy of plant cell walls. This in turn supports multicellular morphogenetic events, such as tissue folding, which further consolidates the stress pattern. Interestingly, and depending on stress magnitude, this mechanical feedback loop may also add robustness to individual cell shapes. We also found that this mechanical feedback loop promotes growth heterogeneity in tissues. We propose that the maintenance of a basal level of growth heterogeneity potentiates organogenesis and in turn fuels a shape-sensing mechanisms to trigger growth arrest. More recently, we started to analyze the contribution of mechanical signals in controlling gene expression patterns and cell fate within the meristem, the plant stem cell niche.
As a PhD student working with Véronique Pautot (INRA, Versailles) and Gerrit Beemster (VIB, Ghent, Belgium), he studied the regulation of meristem function by a set of highly conserved transcription factors in Arabidopsis. He notably showed a role of the gaseous hormone ethylene in regulating the function of homeodomain proteins. He then moved to a completely different field, meiosis in maize, with the group of Zac Cande at UC Berkeley (USA), where he identified and characterized the first plant shugoshin, a protein controlling chromosome segregation. After this, he moved to Lyon (France), where he started his current work on the role of mechanical signals in plant morphogenesis, bridging molecular and cellular biology with modeling and biophysics. He received a number of awards, including “laurier jeune chercheur” from INRA and the Paul Doisteau – Emile Blutet prize from the French science academy. He now holds a research director position at the Plant Reproduction and Development lab (Lyon).
Development relies on a complex network of molecular effectors that ultimately modify the mechanical properties of cells and control shape changes. In turn, mechanical forces can also exert a feedback on the molecular network to channel development. Several mechanosensitive proteins have been identified in animals but their role in multicellular development remains poorly documented. Plants are ideal systems to study mechanotransduction in development because their mechanics are mainly mediated by the cell wall. We have already characterized the response of microtubules to mechanical stress using a set of micromechanical tools (e.g. Hamant et al., 2008 Science, Uyttewaal et al., 2012 Cell) and we are now exploring the many implications of these mechanical feedbacks in the robustness of shape changes in plants. In parallel, we have started to explore how these mechanical signals are transduced molecularly, thus formally integrating the role of mechanotransduction in plant development, with a focus on the shoot apical meristem.
|連絡先||附属社会創造数学研究センター データ数理研究分野 小松﨑民樹|