Journal Article

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

Merlini, Laura, Vincenzetti, Vincent, Martin, Sophie G., Dudin, Omaya, Groux, Raphaël, Bendezú, Felipe O.

2017

Overview

In non-motile fungi, sexual reproduction relies on strong morphogenetic changes in response to pheromone signaling. We report here on a systematic screen for morphological abnormalities of the mating process in fission yeast Schizosaccharomyces pombe. We derived a homothallic (self-fertile) collection of viable deletions, which, upon visual screening, revealed a plethora of phenotypes affecting all stages of the mating process, including cell polarization, cell fusion and sporulation. Cell fusion relies on the formation of the fusion focus, an aster-like F-actin structure that is marked by strong local accumulation of the myosin V Myo52, which concentrates secretion at the fusion site. A secondary screen for fusion-defective mutants identified the myosin V Myo51-associated coiled-coil proteins Rng8 and Rng9 as critical for the coalescence of the fusion focus. Indeed, rng8Δ and rng9Δ mutant cells exhibit multiple stable dots at the cell-cell contact site, instead of the single focus observed in wildtype. Rng8 and Rng9 accumulate on the fusion focus, dependent on Myo51 and tropomyosin Cdc8. A tropomyosin mutant allele, which compromises Rng8/9 localization but not actin binding, similarly leads to multiple stable dots instead of a single focus. By contrast, myo51 deletion does not strongly affect fusion focus coalescence. We propose that focusing of the actin filaments in the fusion aster primarily relies on Rng8/9-dependent cross-linking of tropomyosin-actin filaments.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Actin / Actin Cytoskeleton - genetics / Actin Cytoskeleton - metabolism / Actins - genetics / Amino Acid Sequence - genetics / Biology and Life Sciences / Cell adhesion / Cell Cycle Proteins - genetics / Cell division / Cell fusion / Clonal deletion / Coalescing / Cytoskeleton - genetics / Cytoskeleton - metabolism / Filaments / Fungi / Genetic aspects / Localization / Mating / Morphology / Myosin / Myosin Type V - genetics / Myosin Type V - metabolism / Myosins - genetics / Phenotype / Pheromones / Physiological aspects / Polarization / Protein Binding / Reproduction - genetics / Research and Analysis Methods / Schizosaccharomyces - genetics / Schizosaccharomyces pombe Proteins - genetics / Secretion / Sequence Deletion / Sexual reproduction / Signal transduction / Sporulation / Tropomyosin / Visual perception / Yeast / Yeasts (Fungi)