What's important for sex

Abstract

Sexual reproduction is one of the key features of eukaryotic organisms, essential for survival and evolution of most species. Although the mechanisms of sexual reproduction are largely conserved across all eukaryotes, our understanding of the molecular machinery governing sexual reproduction remains incomplete. This study examines the role of ifs1 in sexual reproduction using fission yeast Schizosaccharomyces pombe as the model system. ifs1 was identified as one of the hits of a genetic screen to identify all the genes contributing to sexual reproduction in fission yeast. I have utilized fluorescence microscopy to study the involvement of ifs1 in different stages of sexual reproduction and found that ifs1 is required for the formation of a functional spore wall. ifs1DEL mutants form spores with an irregular morphology and very low viability. I have used electron microscopy to reveal that the ifs1DEL mutants form a weak spore wall with non-uniform thickness. Spores lacking ifs1 form a bud-like outgrowth on the surface, which enlarges till the spore wall ruptures, allowing the cytoplasmic material to escape. I characterized the composition of the spore wall using FTIR spectroscopy and found that ifs1 is required for b-glucan assembly in the spore wall. In addition, I have engineered single-site mutants of Ifs1 protein to characterize its biochemical activity and have revealed that the highly conserved pyrophosphatase domain of Ifs1 is not required for its role in spore wall formation. Furthermore, my data suggest fission yeast spore walls have three layers, as opposed to the previously hypothesized two-layer model.