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Updated: Jul 4, 2026
Microscopy of Fission Yeast Sexual Lifecycle
Published on: March 9, 2016
Live observation of forespore membrane formation in fission yeast
Taro Nakamura1, Haruhiko Asakawa, Yukiko Nakase
1Department of Biology, Graduate School of Science, Osaka City University, Osaka 558-8585, Japan. taronaka@sci.osaka-cu.ac.jp
Abstract:
Sporulation in the fission yeast Schizosaccharomyces pombe is a unique biological process in that the plasma membrane of daughter cells is assembled de novo within the mother cell cytoplasm. A double unit membrane called the forespore membrane (FSM) is constructed dynamically during meiosis. To obtain a dynamic view of FSM formation, we visualized FSM in living cells by using green fluorescent protein fused with Psy1, an FSM-resident protein, together with the nucleus or microtubules. The assembly of FSM initiates in prophase II, and four FSMs in a cell expand in a synchronous manner at the same rate throughout meiosis II. After the meiosis II completes, FSMs continue to expand until closure to form the prespore, a spore precursor. Prespores are initially ellipsoidal, and eventually become spheres. FSM formation was also observed in the sporulation-deficient mutants spo3, spo14, and spo15. In the spo15 mutant, the initiation of FSM formation was completely blocked. In the spo3 mutant, the FSM expanded normally during early meiosis II, but it was severely inhibited during late and postmeiosis, whereas in the spo14 mutant, membrane expansion was more severely inhibited throughout meiosis II. These observations suggest that FSM expansion is composed of two steps, early meiotic FSM expansion and late and post meiotic FSM expansion. Possible regulatory mechanisms of FSM formation in fission yeast are discussed.
Insights
Fission yeast sporulation involves unique de novo forespore membrane (FSM) assembly. This study visualizes FSM dynamics, revealing distinct early and late expansion phases critical for spore formation.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Sporulation in Schizosaccharomyces pombe involves de novo assembly of the forespore membrane (FSM) within the mother cell.
- Understanding FSM formation dynamics is crucial for comprehending yeast sexual reproduction and cell differentiation.
Purpose of the Study:
- To dynamically visualize forespore membrane (FSM) formation during fission yeast sporulation.
- To investigate the temporal regulation and distinct phases of FSM expansion.
- To analyze the roles of specific sporulation mutants (spo3, spo14, spo15) in FSM assembly.
Main Methods:
- Live-cell imaging of FSM formation using green fluorescent protein (GFP) fused to the FSM-resident protein Psy1.
- Simultaneous visualization of the nucleus and microtubules to correlate FSM dynamics with meiotic progression.
- Analysis of FSM formation in wild-type and sporulation-deficient mutants (spo3, spo14, spo15).
Main Results:
- FSM assembly initiates in prophase II, with four FSMs expanding synchronously and at a constant rate throughout meiosis II.
- FSMs continue to expand post-meiosis II until closure, forming ellipsoidal prespores that mature into spheres.
- Mutant analysis revealed distinct defects: spo15 blocked initiation, spo3 inhibited late/post-meiotic expansion, and spo14 showed severe inhibition throughout meiosis II.
Conclusions:
- FSM expansion comprises at least two distinct steps: early meiotic and late/post-meiotic phases.
- Specific genes (SPO3, SPO14, SPO15) play critical, stage-specific roles in regulating FSM expansion.
- The findings provide insights into the complex regulatory mechanisms governing de novo membrane formation during yeast sporulation.
