Cell–cell fusion is central for sexual reproduction, and generally involves gametes of different shapes and sizes. In walled fission yeast Schizosaccharomyces pombe, the fusion of h+ and h− isogametes requires the fusion focus, an actin structure that concentrates glucanase-containing vesicles for cell wall digestion. Here, we present a quantitative correlative light and electron microscopy (CLEM) tomographic dataset of the fusion site, which reveals the fusion focus ultrastructure. Unexpectedly, gametes show marked asymmetries: a taut, convex plasma membrane of h− cells progressively protrudes into a more slack, wavy plasma membrane of h+ cells. Asymmetries are relaxed upon fusion, with observations of ramified fusion pores. h+ cells have a higher exo-/endocytosis ratio than h− cells, and local reduction in exocytosis strongly diminishes membrane waviness. Reciprocally, turgor pressure reduction specifically in h− cells impedes their protrusions into h+ cells and delays cell fusion. We hypothesize that asymmetric membrane conformations, due to differential turgor pressure and exocytosis/endocytosis ratios between mating types, favor cell–cell fusion.
Ultrastructural plasma membrane asymmetries in tension and curvature promote yeast cell fusion
W. Kukulski’s present address is Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.
- Award Id(s): 310030B_176396
- Award Id(s): MC_UP_1201/8
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Olivia Muriel, Laetitia Michon, Wanda Kukulski, Sophie G. Martin; Ultrastructural plasma membrane asymmetries in tension and curvature promote yeast cell fusion. J Cell Biol 4 October 2021; 220 (10): e202103142. doi: https://doi.org/10.1083/jcb.202103142
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