Kalina Haas winner of an ERC Starting Grant with the STORMtheWALL project

Resolving the mechanism of plant cell expansion with high spatio-temporal resolution.

Kalina Haas has recently joined the "Primary Cell Wall" (PAR) team at the IJPB, as a Research Scientist ("Chargée de recherche"). With her background in physics and quantitative biology in neurosciences, she brings in unique and complementary skills in optics, the use of biosensors and computational modeling. Her 5-year ERC Young Investigator Starting Grant entitled “STORMtheWALL” will provide funding for the recruitment of a team and the acquisition of next generation super-resolution microscopy equipment.    

STORMtheWALL Project
How plants grow constitutes a major frontier in plant research.               
Growth is a multi-scale process; at a subcellular scale, it depends on the expansion of the cell walls, which involves changes in the chemistry and architecture of constituent polymer networks. Little is known on the nature and the control of the cell wall changes that are critical for growth, in striking contrast to the, often detailed, knowledge of growth-regulating signaling networks. This is in part due to the lack of appropriate tools to study changes in the complex cell wall polymer assemblies that often occur at fast (~s) and small (<micrometer) scales.

STORMtheWALL firstly aims to breach the spatial limits of the tools by using multi-target optical nanoscopy to visualize cell wall architecture and remodeling, and secondly, to overcome their temporal limits by using light-gated actuators and multiplexed intracellular biosensors to simultaneously perturb and monitor the system dynamics in vivo. In particular, this project will address pectin remodeling, the role of which in plant growth was shown to be critical, but without clearly understanding the mechanism.  

STORMtheWALL will provide an essential framework, not only for understanding plant growth and morphogenesis but also for the study of life beyond the plasma membrane, for instance in relation to immunity, multicellularity, or symbiosis. 

This project will open a new dimension for the nanoscale understanding of the cell wall and unravel a novel pectin-based mechanism of its active reorganization. STORMtheWALL will provide realistic models for plant cell wall architecture. Such models are an essential brick in multiscale models predicting crop growth and yield in changing environments.

Plant cell wall and growth, to know more about it
One of the fascinating aspects of plants is how the remarkable diversity of shapes and       sizes of plant organs is obtained exclusively through the growth and division of pressurized cells that are surrounded and glued together by strong cell walls. In this respect, a central question, which applies to all walled organisms, is how cells can expand while maintaining the mechanical integrity of their cell wall. Answering this simple question is extremely challenging, not only due to the daunting complexity of the cell wall polymer networks but also because it requires integrating processes occurring at multiple spatial (molecule, wall, cell, organ, plant) and temporal (from milliseconds to days) scales. As a result, despite often detailed knowledge of growth-controlling signaling networks, we actually don't know on which critical cell wall-associated physicochemical processes they impinge, simply because we still mostly remain in the dark on what they are. This is a major obstacle to reliably model and predict plant growth responses to changing environments. The walls of growing plant cells mostly consist of carbohydrate polymers, notably cellulose and the matrix polymers hemicelluloses and pectins, with small amounts of glycoproteins. Changes in the polymer composition and architecture are known to occur during cell expansion, but it is often impossible to distinguish cause from consequence because of the presence of feedback mechanisms that monitor cell wall properties and elicit compensatory modifications.  

Kalina Haas mini-CV
2021 - Permanent position at IJPB, INRAE, Versailles, as Research scientist. She developped the topic "From wall nanostructure to signaling and growth in plants"
2020 - INRAE ERC tenure track researcher, IJPB, INRAE, Versailles
2019 - Post-doctoral position, IJPB, INRAE, Versailles
2018 - Post-doctoral position, University Paris Diderot, Paris University today
2013 - Post-doctoral position, on DNA damage repair and developed strategies for multiplexed biosensing, Hutchison Cancer Unit, Cambridge University
2013 - PhD, has studied the molecular organization of synapses using super-resolution microscopy, University of Bordeaux 2010 - Master's degree in physics, University of Warsaw, Poland

Kalina Haas winner of an ERC Starting Grant with the STORMtheWALL project

B: Lobed leaf epidermal anticlinal (normal to the surface) cell wall imaged with 3D dSTORM super-resolution*, with methylated (pink) and fully demethylated (green) pectin homogalacturonan (HG) C: partially methylated (pink) and fully demethylated (green) HG.
* dSTORM is a super-resolution fluorescence microscopy method, based on single molecule localisation

Breakthrough in 2020,
the cell wall is acting to define the cell shape, news 27/01/2020