Robust gradient formation in the fission yeast
Fission yeast is a rod-shaped unicellular organism that grows until it reaches about 14 microns and then divides. But wait, how does fission yeast measure it’s own size? We don’t exactly know yet. But one important player seems to be Pom1 a protein that is brought to the two poles of the cell and diffuses along the membrane to the cell center. While diffusing, Pom1 also auto-phosphorylates and detaches from the membrane, resulting in a double Pom1 concentration gradient from the poles to the center. Moreover Pom1 inhibits Cdr2, a protein that triggers the cell division. As an analogy, you can imagine a growing metallic rod which breaks below a certain temperature. If you heat the rod at the two tips, the temperature in the middle of the rod will decrease as the rod grows until it breaks – in the middle, as it is the coolest point, and always at the same size, if the rod receives the same amount of heat at the tips. And that is where our work started, since it was observed that the amount of Pom1 brought to the tips differs greatly across and within cells.
This project was a collaboration with Olivier Hachet from the lab of Sophie Martin at UNIL.