Cell wall heterogeneity during root growth
Plant Genetics and Genomics
Plant Physiology
Final Report Abstract
The plant cell wall is a highly complex structure, made up mostly of different polysaccharides, the main ones being cellulose, hemicellulose and pectin. In generalized models of plant cell walls, cellulose is depicted as long microfibrils, which act as the load bearing scaffold of the wall. The cellulose microfibrils are interconnected by hemicelluloses (xyloglucans in primary cell walls; xylans in secondary walls), which provide additional stability. The large group of pectic polysaccharides form an amorphous matrix, which embeds the cellulose-hemicellulose structure and seals off the wall. While this model is generally correct, it must also be assumed that cell walls of cells in different developmental stages, or with different specializations, have different structural properties and compositions. In this project we set out to analyse such differences. We subjected plants to different stimuli, which we expected to impact the plant cell wall, such as changes in the plants graviresponse, induced cell wall synthesis in cells lacking a wall, changes to the environment, or a pathogenic attack. We found that the cell’s response to changes in the gravitropic vector includes re-orientation of the cellulose microfibrils and changes in hemicellulosic mannan content, both affecting the walls stiffness and allowing the plant to adjust its growth according to the changes in graviperception. We also identified a master transcriptional regulator triggering the primary cell wall synthesis program, which we used to induce primary cell walls in cell regions that would normally form secondary cell walls. Using this we found that some aspects of cell wall synthesis are guided by such a developmental switch, while others are directed by the cell’s environment. Analysing plant mutants for a putative cell wall integrity sensor, we identified a pathway that adjusts cell growth to changes in environmental pH, by regulating proton-pumps and calcium-influx, thereby neutralizing a pH gradient that formed across the plasma membrane because of the acidification of the environment. Finally, we initiated a project visualizing damages done to the cell wall by a fungal pathogen, as well as the cell’s response to these damages, using custom-built microscopic tools. We believe that the work done in this project will contribute to a more detailed understanding of plant cell wall structure, which will eventually show that plant cell walls are not just a homogenous barrier, but a sensory platform with complex heterogeneities between different cells and cell types.
Publications
- (2018) A short history of Arabidopsis thaliana (L.) Heynh. Columbia-0. PeerJ Prepr.: 1–7
Somssich M.
(See online at https://doi.org/10.7287/peerj.preprints.26931) - (2018) A short history of the CaMV 35S Promoter. PeerJ Prepr.: 1–16
Somssich M.
(See online at https://doi.org/10.7287/peerj.preprints.27096) - (2018). Building a plant cell wall at a glance. J. Cell Sci. 131
Lampugnani, E. R., Khan, G. A., Somssich, M., and Persson, S.
(See online at https://doi.org/10.1242/jcs.207373) - (2018). Complete substitution of a secondary cell wall with a primary cell wall in Arabidopsis. Nature Plants
Sakamoto S., Somssich M., Nakata M.T., Unda F., Atsuzawa K., Kaneko Y., et al.
(See online at https://doi.org/10.1038/s41477-018-0260-4) - (2019) A short history of Plant Transformation. PeerJ Prepr.: 1–28
Somssich M.
(See online at https://doi.org/10.7287/peerj.preprints.27556) - (2019). Brassinosteroids Influence Arabidopsis Hypocotyl Graviresponses Through Changes In Mannans And Cellulose. bioRxiv.: 1-37
Somssich, M., Vandenbussche, F., Ivakov, A., Funke, N., Ruprecht, C., Vissenberg, K., et al.
(See online at https://doi.org/10.1101/557777) - (2020) A short history of Vernalization. Zenodo: 1–28
Somssich M.
(See online at https://doi.org/10.5281/zenodo.3660691) - (2020). Plant Science’s Next Top Models. Annals of Botany
Cesarino, I., Dello Ioio, R., Kirschner, G. K., Ogden, M. S., Picard, K. L., Rast-Somssich, M. I., and Somssich, M.
(See online at https://doi.org/10.1093/aob/mcaa063)
