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The fission yeast Schizosaccharomyces pombe is an important model organism for the study of eukaryotic molecular and cellular biology. Studies of S. pombe, together with studies of its distant cousin, Saccharomyces cerevisiae, have led to the discovery of genes involved in fundamental mechanisms of transcription, translation, DNA replication, cell cycle control, and signal transduction, to name but a few processes. However, since the divergence of the two species approximately 350 million years ago, S. pombe appears to have evolved less rapidly than S. cerevisiae so that it retains more characteristics of the common ancient yeast ancestor, causing it to share more features with metazoan cells. This Primer introduces S. pombe by describing the yeast itself, providing a brief description of the origins of fission yeast research, and illustrating some genetic and bioinformatics tools used to study protein function in fission yeast. In addition, a section on some key differences between S. pombe and S. cerevisiae is included for readers with some familiarity with budding yeast research but who may have an interest in developing research projects using S. pombe.

We identified the phhl ÷ gene that encodes a MAP kinase as the effector of Wisl MAP kinase kinase in fission yeast, which is highly homologous with HOG1 of S. cerevisiae. Heterothalic phhl dsiruptant is phenotypically indistinguishable from wisl deletion mutant, both displaying the same extent of partial sterility and enhanced sensitivity to a variety of stress. In phhl disruptant, nitrogen starvation-induced expression of stell +, a key controller of sexual differentiation, is markedly diminished. Ectopic expression of stell ÷ effectively restores fertility, but not stress resistance, to the phhl disruptant. These data show that stress signal, mediated by a MAP kinase, is required for efficient start of sexual differentiation.

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