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S. pombe sporulation-specific coiled-coil protein Spo15p is localized to the spindle pole body and essential for its
S Ikemoto1, T Nakamura, M Kubo
1Department of Biology, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan.
Abstract:
Spindle pole bodies in the fission yeast Schizosaccharomyces pombe are required during meiosis, not only for spindle formation but also for the assembly of forespore membranes. The spo15 mutant is defective in the formation of forespore membranes, which develop into spore envelopes. The spo15(+)gene encodes a protein with a predicted molecular mass of 223 kDa, containing potential coiled-coil regions. The spo15 gene disruptant was not lethal, but was defective in spore formation. Northern and western analyses indicated that spo15(+) was expressed not only in meiotic cells but also in vegetative cells. When the spo15-GFP fusion gene was expressed by the authentic spo15 promoter during vegetative growth and sporulation, the fusion protein colocalized with Sad1p, which is a component of spindle pole bodies. Meiotic divisions proceeded in spo15delta cells with kinetics similar to those in wild-type cells. In addition, the morphology of the mitotic and meiotic spindles and the nuclear segregation were normal in spo15delta. Intriguingly, transformation of spindle pole bodies from a punctate to a crescent form prior to forespore membrane formation was not observed in spo15delta cells. We conclude that Spo15p is associated with spindle pole bodies throughout the life cycle and plays an indispensable role in the initiation of spore membrane formation.
Insights
Spo15p is crucial for initiating spore membrane formation in fission yeast, associating with spindle pole bodies throughout the cell cycle. This protein is essential for proper spore development during meiosis.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Spindle pole bodies (SPBs) in Schizosaccharomyces pombe are vital for spindle formation and forespore membrane assembly during meiosis.
- The spo15 mutant exhibits defects in forespore membrane development, which is essential for spore envelope formation.
Purpose of the Study:
- To investigate the function of the spo15(+) gene and its encoded protein, Spo15p, in fission yeast.
- To determine the role of Spo15p in SPB function and spore formation.
Main Methods:
- Gene disruption and analysis of the spo15 null mutant (spo15delta).
- Northern and western blot analyses to assess spo15(+) expression.
- Construction and expression of a spo15-GFP fusion protein.
- Microscopic observation of mitotic and meiotic spindles, nuclear segregation, and SPB morphology.
Main Results:
- The spo15 gene disruptant was viable but defective in spore formation.
- Spo15p is expressed in both meiotic and vegetative cells.
- Spo15-GFP localized to SPBs, colocalizing with Sad1p.
- Meiotic divisions, spindle morphology, and nuclear segregation were normal in spo15delta cells.
- The characteristic transformation of SPB morphology prior to forespore membrane formation was absent in spo15delta cells.
Conclusions:
- Spo15p is associated with spindle pole bodies throughout the fission yeast life cycle.
- Spo15p plays an essential role in initiating the formation of spore membranes during meiosis.