Fundamental limits to organelle biogenesis control in <i>Saccharomyces cerevisiae</i>

Among the most important processes in the self-assembly of the eukaryotic cell is the synthesis of its organelles, specialized biochemical compartments that house processes crucial to cellular physiology. Two critical properties closely linked with organelle function are their copy numbers and sizes. Numerous molecular factors that regulate the numbers and sizes of a diverse array of organelles, including the Golgi, mitochondria, peroxisomes and lipid droplets among others, have been identified. However, our understanding of the quantitative principles governing organelle number and size control remains incomplete. Here, we combine experimental data from the single-celled eukaryote Saccharomyces cerevisiae and mathematical theory to show that cells tolerate substantial fluctuations in organelle number while robustly controlling fluctuations in organelle sizes. In particular, our framework suggests that organelle size increases in random bursts from a limited pool of building blocks, which in turn imposes an asymmetry in optimal organelle number and size control. Burst like growth is a potentially general mechanism by which the cell efficiently assembles subcellular structures from its finite resources.