Phosphatidylethanolamine Is Required for Normal Cell Morphology and Cytokinesis in the Fission Yeast, Schizosaccharomyces pombe

We describe the characterization of three predicted genes, designated psd1‐3 , in the fission yeast, Schizosaccharomyces pombe , encoding phosphatidylserine decarboxylases (PSDs), which catalyze the conversion of phosphatidylserine to phosphatidylethanolamine (PE). While S. pombe mutants carrying deletions in any one or two psd genes are viable in both rich and minimal media, psd1‐3δ mutants carrying deletions in all three psd genes grow slowly in rich medium and are inviable in minimal medium, indicating that the psd1‐3 gene products share overlapping essential cellular functions. Supplementation of growth media with ethanolamine, which can be converted to PE by the Kennedy pathway, restores growth to psd1‐3δ cells in minimal medium, indicating that PE is essential for S. pombe cell growth. psd1‐3δ cells appear morphologically indistinguishable from wild type S. pombe cells in medium supplemented with ethanolamine but when cultured in non‐supplemented medium produce high frequencies of abnormally shaped cells as well as cells exhibiting severe septation defects, including multiple, mispositioned, deformed, and misoriented septa. Our results demonstrate that PE is essential for cell growth and for normal morphology and cytokinesis in S. pombe and illustrate the usefulness of this model eukaryote for investigating potentially conserved biological and molecular functions of PE.