Biophysics and Development

We study morphogenesis in plants, notably at the shoot apex of Arabidopsis. We focus on robustness of morphogenesis, by analyzing cellular variability and exploring mechanisms that enhance or buffer such variability. To do so, we combine approaches from molecular biology, live imaging, biophysics, data analysis, and modeling. We address these questions and use these approaches in four main topics:
- Mechanics of morphogenesis
- Floral Growth Patterns
- Gene Regulatory Networks
- Modelling Plant Morphogenesis

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Mechanics of Morphogenesis

Leader : Arezki Boudaoud

PNG - 23.1 kb Morphogenesis is the remarkable process by which a developing organism acquires its shape. While molecular and genetic studies have been highly successful in explaining the cellular basis of development and the role of biochemical gradients in coordinating cell fate, understanding morphogenesis remains a central challenge for both developmental biology and biophysics. Indeed, shape is imposed by structural elements, so that an investigation of morphogenesis must address how these elements are controlled at the cell level, and how the mechanical properties of these elements lead to specific growth patterns. Using plants as model systems, we tackle the following questions. (i) Does the genetic and molecular identity of a cell correspond to a mechanical identity. (ii) Do the mechanical properties of the different cell domains predict shape changes. (iii) How does the intrinsic stochasticity of cell mechanics and cell growth lead to reproducible shapes?

Floral Growth Patterns

Leader : Pradeep Das

PNG - 31.8 kb The emergence of stereotypical shapes and sizes of tissues and organs requires the coordinated regulation of very specific growth patterns across space and time during development. We seek to gain a clear understanding of how the underlying molecular, genetic and physical events govern growth. The most obvious way to measure and describe growth is at the cellular level. Over the last several years, we have developed a software pipeline to computationally track the growth of Arabidopsis flowers at cell resolution and in 4 dimensions (space and time; Fernandez et al., Nature Methods, 2010). We are now in the process of using segmented time course data to statistically analyse floral growth leading up to the first morphogenetic events. Naturally, these patterns are a result of the genetic and mechanical events occurring during development. To this end, we are also examining the link between growth and patterning, and between patterning and mechanics.

Gene Regulatory Networks

Leader : Françoise Monéger

PNG - 38 kb We also perform modeling on gene regulatory networks and develop approaches aiming at integrating different types of data (expression patterns, direct interactions, genetic interactions) in an integrative coherent model. More recently, we focused on the cell wall and on the enzymes involved in cell wall remodeling in order to understand how molecular networks and transcription factors in particular control flower morphogenesis. Our project aims at identifying among 30 transcription factors expressed in the flower, the target genes encoding protein involved in cell wall and try to understand how the regulation of the expression of these genes leads to the control of the flower shapes.

Modelling Plant Morphogenesis

Leader : Annamaria Kiss

PNG - 17.9 kb In order to be able to model the emergence of an organ’s shape, it is essential to begin with the analysis of data in connection with morphogenesis. Therefore we develop tools for image segmentation (level set, MARS on Openalea) and for data analysis (plugin on MorphoGraphX) and specifically, we carry out the quantitative and statistical analyses of serial images of developing organs, such as leaves, flowers or meristems. In parallel, we are also studying mechanical models of plant tissue. The goal is first to infer mechanical properties from images, and then, using these properties we are seeking to reproduce by modelling the emergence of forms at the tissular level.









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