The neutral lipids steryl ester and triacylglycerol (TAG) are stored in the membrane-bound organelle lipid droplet (LD) in essentially all eukaryotic cells. It is unclear what physiological conditions require the mobilization or storage of these lipids. Here, we study the budding yeast mutant are1Δ are2Δ dga1Δ lro1Δ, which cannot synthesize the neutral lipids and therefore lacks LDs. This quadruple mutant is delayed at cell separation upon release from mitotic arrest. The cells have abnormal septa, unstable septin assembly during cytokinesis, and prolonged exocytosis at the division site at the end of cytokinesis. Lipidomic analysis shows a marked increase of diacylglycerol (DAG) and phosphatidic acid, the precursors for TAG, in the mutant during mitotic exit. The cytokinesis and separation defects are rescued by adding phospholipid precursors or inhibiting fatty acid synthesis, which both reduce DAG levels. Our results suggest that converting excess lipids to neutral lipids for storage during mitotic exit is important for proper execution of cytokinesis and efficient cell separation.
© 2016 Yang et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).