Calcium signalling plays a key role in the development of patterning and morphogenesis in early embryos in ascidians, frogs, and zebrafish, but the link underlying calcium signalling and morphogenesis is not known. During this project, we developed a device able to apply localized forces at the shoot apical meristem of plants. We show that such mechanical perturbation is sufficient to induce a calcium wave across the meristem. Moreover we provided a new framework for the function of calcium signals in cellular polarity during organ initiation.
In addition, we designed a specific device able to stretch a single protoplast and measure the applied force under confocal observation. Using this new device, we show for the first time that single plant protoplast responds to stretching and that calcium is released in its cytoplasm at a specific threshold force.
So far, our work on the experimental technique to culture single cells into defined shapes led to new findings on how the cytoskeleton of plant cells reacts to different shapes. We now plan to couple our micro-wells design with a microfluidic device to bring a constant nutrient intake allowing the protoplasts to regenerate their cell wall inside the micro-wells. There is no doubt that the establishment of this new device will be useful for many applications and many walled cell organisms, broadening the impact of this project. We also plan to perform Atomic Force Microscopy (AFM) measurements on regenerating protoplasts inside the wells to quantify the evolution of the cell wall stiffness during this process. By correlating this quantification with microscopic observations we will assess the role of each components of the cell wall in establishing a robust shape.
By the end of the project we should be able to tell whether mechanical stresses directly control cytoskeletal organisation, thus being at the initiation of cell polarisation or whether the cell wall (and which components) is the initiator of the polarisation then creating a specific stress field during growth that influence cytoskeletal organisation.
By adding a cellular level description, these experiments will be the basis of generating models to test differential feedback mechanisms between cell wall, cytoskeleton and physical forces that determine aspects of plant morphogenesis and development.
The original experimental technique that we developed to culture single cells into defined shapes brings technical innovation and could be of use for mechanical studies in others walled cell organisms, which also must respond at the cellular level to mechanical forces, thereby broadening the impact of this project and opening up best career possibilities to the researcher.
By quantifying the role of mechanical stresses in plant cell growth and morphogenesis, we strongly believe that the approach developed in this project will bring new knowledge in plant development. The issues of this research could find numerous applications in developing new agricultural techniques without having to deal with genetically modified organism.
This particular interdisciplinary competence that the researcher will use throughout her future career will have broad scientific and technological benefits for European research with application to a broad range of fields in developmental biology. More precisely, the future research activity of the beneficiary on the role of mechanical signals in plant growth could generate technological innovation in agronomy and agriculture (crop yield, fruits size...) with an impact on the economy of the European society. During her future career, she also plans to work on the role of mechanics in the morphogenesis of other organisms (diatoms, unicellular algae or micro-organisms), which could lay a foundation for biotechnology and biomaterial innovations.
