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Tanguy Dufourt
What are the mechanisms underlying position and orientation of cytokinetic plane in brown algae embryos ?
Progress of my phd
During my PhD, I am trying to understand the intracellular mechanisms that explain the position and orientation of the cell division plane during the embryogenesis of brown algae. In brown algae, there are two centrosomes during almost the entire cell cycle. The cell division plane is always perpendicular and centred on the axis connecting the two centrosomes. (Katsaros, 2012).
The candidate mechanisms explaining the position and orientation of the cell division plane are cortical pushing and cortical pulling. (Grill & Hyman, 2005). In cortical pushing, astral microtubules emerging from the centrosomes push until they come into contact with the plasma membrane. The plasma membrane reacts by exerting a force in the opposite direction to the growth of the microtubules, which has the effect of moving the centrosome away from the plasma membrane and thus centring the centrosomes within the cell if it has a simple shape (spherical, cuboid, etc.). In cells with a more complex shape (cylindrical, hemispherical, etc.), cortical pushing alone is not sufficient to centre the centrosomes within the cell. The second mechanism, cortical pulling, then becomes obvious. In cortical pulling, the astral microtubules emerging from the centrosomes will push until they come into contact with the plasma membrane. The microtubule is likely to come into contact with a molecular motor grafted into the cell cortex. To perform pulling, this molecular motor must pull on the microtubule and therefore move towards the minus end of the microtubule: this is the case with dynein.
I checked whether dynein was present in brown algae. Based on data from the PhaeoExplorer project (Denoeud et al., 2024), I observed the presence of all dynein subunits in brown algae. Furthermore, dynein is a highly conserved molecular motor in all organisms that have dynein. What makes dynein specific is its interaction with a cargo adaptor protein. There are 15 proteins known to be cargo adaptors in animals. (Reck-Peterson et al., 2018). Of these 15 proteins, I have identified only one: HOOK. The presence of functional dynein leads me to believe that there are cargo adaptors specific to brown algae that have not yet been discovered.
In animals, dynein can be grafted onto the cell cortex via an LGN-NuMA complex. (Zhong et al., 2022). The LGN-NuMA complex is linked to dynein on one side and filamentous actin on the other. I sought to observe the position of filamentous actin in Sphacelaria rigidula. Given the difficulty of observing such cytosolic elements, I focused more on modelling using Cytosim software. (Nedelec & Foethke, 2007). I had to adapt Cytosim to make it usable with the various forms of my species of brown algae of interest: Saccharina latissima, Fucus serratus and Sphacelaria rigidula. I then implemented cortical pushing and cortical pulling in Cytosim. This led to the creation of a poster presented at the EvoLyon conference on 4 November 2025 at INSA Lyon.
Presentations
- 2025: T. Dufourt, M. Zilliox, B. Billoud, D. Grossman, R. Milstein, B. Charrier. What mechanisms underlie the positioning and orientation of the cell division plane in brown algae? European Plant Cytoskeleton Club, 4-5 september 2025, ENS-Lyon, Lyon, France.
- 2023: B. Charrier, B. Billoud, T. Dufourt, I. Theodorou. Modelling the change in orientation of cell division in brown algae. IRN France-Japan Frontiers in Plant Biology (FJFPB) Symposium, 22-24 october 2023, Kyoto, Japan.
Posters
- 2025: T. Dufourt, B. Billoud, B. Charrier. The central role of dynein in brown algae cell division. Biennial meeting "Evolyon", 4 november 2025, INSA Lyon, Lyon, France.
- 2025: T. Dufourt, B. Billoud, B. Charrier. Mechanisms that explain the position and the orientation of the cell division plane in brown algae. BioSymposium, 27 march 2025, ENS Lyon, Lyon, France.
- 2024: T. Dufourt, B. Billoud, B. Charrier. Modelling of the positioning of the division plane in brown algae. Mechano-Biology and Physics of Life (6ème édition), 25 january 2024, Grenoble, France.
- 2023: T. Dufourt, B. Charrier, B. Billoud. How can Cytosim be useful to predict the position of the cytokinetic plan in brown algal cells: the Alter-eCyto project. 13Ème journées du réseau André Picard, 26-27 march 2023, Paris, France.
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