An organelle inheritance pathway during polarized cell growth

Abstract

Some organelles cannot be synthesized anew, so they are segregated into daughter cells during cell division. In Saccharomyces cerevisiae, daughter cells bud from mother cells and are populated by organelles inherited from the mothers. To determine whether this organelle inheritance occurs in a stereotyped manner, we tracked organelles using fluorescence microscopy. We describe a program for organelle inheritance in budding yeast. The cortical endoplasmic reticulum (ER) and peroxisomes are inherited concomitant with bud emergence. Next, vacuoles are inherited in small buds, followed closely by mitochondria. Finally, the nucleus and perinuclear ER are inherited when buds have nearly reached their maximal size. Because organelle inheritance timing correlates with bud morphology, which is coupled to the cell cycle, we tested whether organelle inheritance order is controlled by the cell cycle. By arresting cell cycle progression but allowing continued bud growth, we determined that organelle inheritance still occurs without cell cycle progression past S-phase, and that the general inheritance order is maintained. Thus, organelle inheritance follows a preferred order during polarized cell division, but it is not controlled exclusively by cell cycle signaling. Summary statementOrganelles are interconnected by contact sites, but they must be inherited from mother cells into buds during budding yeast mitosis. We report that this process occurs in a preferred sequence.