A systematic screen for morphological abnormalities during fission yeast sexual reproduction identifies a mechanism of actin aster formation for cell fusion

• DOI: 10.1371/journal.pgen.1006721
• Publication Date: 2017-04-14T17:33:32Z
• Authors: Omaya Dudin; Laura Merlini; Felipe O. Bendezú; Raphaël Groux; Vincent Vincenzetti; Sophie G. Martin
• Keywords: 0301 basic medicine; 2. Zero hunger; 0303 health sciences; Reproduction; Myosin Type V; Cell Cycle Proteins; QH426-470; Myosins; Actins; Actin Cytoskeleton; 03 medical and health sciences; Phenotype; Schizosaccharomyces; Genetics; Amino Acid Sequence; Schizosaccharomyces pombe Proteins; Cytoskeleton; Research Article; Protein Binding; Sequence Deletion

AbstractIn non-motile fungi, sexual reproduction relies on stron morphogenetic changes in response to pheromone signaling. We report here on asystematic screen for morphological abnormalities o the mating process in fission yeastSchizosaccharomyces pombe. We derived a homothallic (self-fertile) collection of viable deletions which, upon visual screening, revealed a plethora of phenotype affecting all stages of the mating process, including cell polarizati cell fusion and sporulation. Cell fusion relies onthe formation of the fusion focus, an aster-like F-actin structure that is marked by stron local accumulation of the myosin V Myo52, which concentrates secretion at the fusion site. A secondaryscreen for fusion-defective mutants identified the myosin V Myo51-associated coiled-coil proteins Rng8 and Rng9 as critical forthe coalescence of the fusion focus Indeed,rng8∆andrng9∆mutant cells exhibitmultiple stable dots a the cell-cell contact site, instead of the single cusfo observed in wildtype. Rng8 and Rng9 accumulate on the fusion focus, depende on Myo51 and tropomyosin Cdc8A. tropomyosin mutant allele, whic compromises Rng8/9 localization but not actin binding, similarly lea to multiple stable dots instead of a single focus.By contrast,myo51deletion does not strongly affect fusion focus coalescenceWe. propose that focusing of the actinfilaments in the fusionaster primarily relies on Rng8/9-dependent cross-linking of tropomyosin-actin filaments.