Download Postdoc project: Mechanogenetics of plant cells

Postdoc project: Mechanogenetics of plant cells
Duration: Two years, from September 2012
Host Lab/Funding: Ecole Normale Supérieure de Lyon, 46 Allée d’Italie, 69007 Lyon, France. Joint
ANR project between the Physics, the Joliot Curie, and Plant Reproduction and Development
laboratories.
Context: Our main goal is to understand the cellular mechanisms behind morphogenesis. As
classically pictured in the French flag model, growth pattern rely in part on the diffusion of
morphogens in tissues. In addition to these biochemical cues, mechanical forces are emerging as key
signals for many developmental processes, like mitotic spindle orientation in HeLa (human) cells
(THERY et al. 2007) and the expression of patterning genes, like TWIST in Drosophila embryos
(DESPRAT et al. 2008). Patterns of mechanical stress have also been shown to drive specific
morphogenetic events, like the formation of functional boundaries in Drosophila imaginal discs
(LANDSBERG et al. 2009) or the left-right asymmetry in mammal embryos (NONAKA et al. 2002).
Mechanosensitive deformable proteins (GRASHOFF et al. 2010; KELLERMAYER et al. 1997;
OBERHAUSER et al. 1998; RIEF et al. 1997; TSKHOVREBOVA et al. 1997; YONEMURA et al. 2010) and
stretch-activated channels (KUMAMOTO 2008) have been identified, providing the first clues on the
transduction of mechanical signals in the cell.
In the past, the consortium has focused on the shoot apical meristem of Arabidopsis thaliana
and has demonstrated a role of mechanical forces in plant development, notably via the control of the
microtubular cytoskeleton organization (HAMANT et al. 2008 Science) and the distribution of the plant
hormone auxin (HEISLER et al. 2010 PLoS Biol.). Regulators of the cell response to stress start to be
analyzed, notably in relation to growth (UYTTEWAAL et al. 2012 Cell) and atomic force microscopy
approaches are currently used to decipher the link between the mechanical properties of the cells and
patterning/identity (MILANI et al. 2011 Plant J).
Project: In this project, the postdoc will identify mechanosensitive genes (i.e. the expression of which
is modulated by mechanical stress) and decipher how mechanical stress is transduced to the nucleus
(i.e. whether it is transduced via major transduction cascades or via the cytoskeleton continuum
between the plasma membrane to the nuclear envelope). To do so, he/she will analyze the response of
plant cells to mechanical perturbation using various micromechanical tools (nanoindenters,
microfluidic confiners, AFM,…) on Arabidopsis cell cultures. Quasi-static and dynamic experiments
of stress-induced cell deformation will be performed to capture short and long term responses.
Transcriptome of mechanically-induced cells will be obtained by RNAseq and the mechanosensitive
genes will be validated by qRT-PCR. The chromatin signature of these genes will be investigated in
collaboration with the other members of the team. If time allows, the localization of the
mechanosensitive loci within the nucleus will be determined in order to check whether position is
correlated with the mechanical strain rate within the nucleus. To understand how the stress is
transduced to the nucleus, the contribution of the cell wall, the cytoskeleton and other effectors of the
cascades will be tested using mutants and drugs.
Profile: We are looking for a highly motivated biologist with strong involvement in her/his research
project, with good background and practical skills in molecular and cellular biology, and ideally with
experience with micromechanical tools and physical data interpretation. Applications should be sent
by email to [email protected], [email protected] or [email protected] with a CV.
References
DESPRAT, N., W. SUPATTO, P. A. POUILLE, E. BEAUREPAIRE and E. FARGE, 2008 Tissue deformation modulates twist expression to determine anterior midgut differentiation in Drosophila embryos. Dev Cell 15: 470-­‐477. GRASHOFF, C., B. D. HOFFMAN, M. D. BRENNER, R. ZHOU, M. PARSONS et al., 2010 Measuring mechanical tension across vinculin reveals regulation of focal adhesion dynamics. Nature 466: 263-­‐
266. HAMANT, O., M. G. HEISLER, H. JONSSON, P. KRUPINSKI, M. UYTTEWAAL et al., 2008 Developmental patterning by mechanical signals in Arabidopsis. Science 322: 1650-­‐1655. HEISLER, M. G., O. HAMANT, P. KRUPINSKI, M. UYTTEWAAL, C. OHNO et al., 2010 Alignment between PIN1 polarity and microtubule orientation in the shoot apical meristem reveals a tight coupling between morphogenesis and auxin transport. PLoS Biol 8: e1000516. KELLERMAYER, M. S., S. B. SMITH, H. L. GRANZIER and C. BUSTAMANTE, 1997 Folding-­‐unfolding transitions in single titin molecules characterized with laser tweezers. Science 276: 1112-­‐1116. KUMAMOTO, C. A., 2008 Molecular mechanisms of mechanosensing and their roles in fungal contact sensing. Nat Rev Microbiol 6: 667-­‐673. LANDSBERG, K. P., R. FARHADIFAR, J. RANFT, D. UMETSU, T. J. WIDMANN et al., 2009 Increased cell bond tension governs cell sorting at the Drosophila anteroposterior compartment boundary. Curr Biol 19: 1950-­‐1955. MILANI, P., M. GHOLAMIRAD, J. TRAAS, A. ARNEODO, A. BOUDAOUD et al., 2011 In vivo analysis of local wall stiffness at the shoot apical meristem in Arabidopsis using atomic force microscopy. Plant J 67: 1116-­‐1123. NONAKA, S., H. SHIRATORI, Y. SAIJOH and H. HAMADA, 2002 Determination of left-­‐right patterning of the mouse embryo by artificial nodal flow. Nature 418: 96-­‐99. OBERHAUSER, A. F., P. E. MARSZALEK, H. P. ERICKSON and J. M. FERNANDEZ, 1998 The molecular elasticity of the extracellular matrix protein tenascin. Nature 393: 181-­‐185. RIEF, M., M. GAUTEL, F. OESTERHELT, J. M. FERNANDEZ and H. E. GAUB, 1997 Reversible unfolding of individual titin immunoglobulin domains by AFM. Science 276: 1109-­‐1112. THERY, M., A. JIMENEZ-­‐DALMARONI, V. RACINE, M. BORNENS and F. JULICHER, 2007 Experimental and theoretical study of mitotic spindle orientation. Nature 447: 493-­‐496. TSKHOVREBOVA, L., J. TRINICK, J. A. SLEEP and R. M. SIMMONS, 1997 Elasticity and unfolding of single molecules of the giant muscle protein titin. Nature 387: 308-­‐312. UYTTEWAAL, M., A. BURIAN, K. ALIM, B. LANDREIN, D. BOROWSKA-­‐WYKRET et al., 2012 Mechanical Stress Acts via Katanin to Amplify Differences in Growth Rate between Adjacent Cells in Arabidopsis. Cell 149: 439-­‐451. YONEMURA, S., Y. WADA, T. WATANABE, A. NAGAFUCHI and M. SHIBATA, 2010 alpha-­‐Catenin as a tension transducer that induces adherens junction development. Nat Cell Biol 12: 533-­‐
542.