Einfluss der pflanzlichen Zellwand auf Zellpolarisierung und Morphogenese in der Stomata Entwicklung.
Zusammenfassung der Projektergebnisse
All life on earth starts as a single cell. Higher forms of life, like animals and plants take a fascinating path to grow from their unicellular beginnings to functioning breathing organisms. Admittedly, there are striking differences between plants and animals. Not so much the breathing part, but rather the path they take during their development. One has to keep in mind, that plants and animals only share unicellular ancestors and had to figure out all steps that involved the arrangement or more than one cell on their own. The field of science that I am most interested in has to do with the breathing of plants. Plants exchange gases with their environment all the time. Tiny pores in the leaf surface called stomata (Greek for mouths) release oxygen and water vapor and take up carbon dioxide needed for photosynthesis. They thus form the basis for all animal life by feeding the production of energy-rich organic matter with carbon dioxide. Stomata are of enormous relevance for the global climate, too. Every six months all the water in our atmosphere and one fifth of the atmosphere’s carbon passes through them. Given their global importance it surprises how little we know about stomatal development. When a new leaf emerges, it does not have any stomata, yet. The leaf surface (epidermis) at that stage consists of cells that soon enter a developmental program called the stomatal lineage. This program involves a plethora of genetic changes, oriented cell divisions, and cell differentiation. By the time the leaf comes to maturity, over 80% of cells in the leaf epidermis will be derived from the stomatal lineage. The stomatal lineage of Arabidopsis (the model plant we chose to use for our experiments) has two products: puzzle-piece-shaped pavement cells, that make for the bulk of leaf surface area and kidney-shaped guard cells that make the stoma. In order to have this two-cell-outcome, a stomatal stem cell called meristemoid undergoes an asymmetric division, leading to two daughter cells, one small, one larger, with different fate. The fate asymmetry is accomplished as the two daughter cells inherit a different set of proteins from the mother cell. Polarized proteins will pick a side before the mother cell divides and the daughter cell that inherits them will soon become a pavement cell, whereas its sister cell will give rise to a pair of guard cells. As described before, plant cells are special in their development. One of their main challenges is that they can’t re-arrange. Due to their cell walls, plant cells keep their position throughout their life. The whole tissue architecture is therefore set at an early developmental stage. This makes communication very important. Meristemoids must know where they are in the tissue, what their neighbors’ identity is, and which direction the whole leaf grows in. At the nexus of all these mechanisms that lead from a few stem cells to a perfectly shaped and functional leaf is the cell wall. The cell wall allows directional growth due to changes in its physical properties like stiffness and rigidity, it transmits diffusible signals from cell to cell and it supports the plant with its load bearing qualities. The DFG supported me in my efforts to investigate the role of the cell wall in stomatal development. During the two years of funding I could make significant contributions to the field: I identified new cell wall associated proteins that are responsible for making new walls in the stomatal lineage. Plants that lack these proteins fail to properly shape and arrange stomata in the leaf surface. I discovered a new role for the cell wall as a signaling compartment in stomatal development. Mechanical forces derived from the constant pushing and pulling between growing cells are conducted through the cell walls and directly influence the deposition of polarized proteins in asymmetric divisions. Through this mechanism tissue wide growth and positional information is communicated to individual cells. I further identified new interaction partners of polarized proteins and hope to use this information to make future contributions to the field of cell polarity and fate.
Projektbezogene Publikationen (Auswahl)
- The Arabidopsis CSLD5 functions in cell plate formation in a cell cycle dependent manner. The Plant Cell Jul 2016, 28 (7) 1722-1737
Fangwei Gu, Martin Bringmann, Jonathon R. Combs, Jiyuan Yang, Dominique C. Bergmann, Erik Nielsen
(Siehe online unter https://doi.org/10.1105/tpc.16.00203)
