title: Organelle size scaling of the budding yeast vacuole is tuned by membrane trafficking rates.
abstract: Organelles serve as biochemical reactors in the cell, and often display characteristic scaling trends with cell size, suggesting mechanisms that coordinate their sizes. In this study, we measure the vacuole-cell size scaling trends in budding yeast using optical microscopy and a novel, to our knowledge, image analysis algorithm. Vacuole volume and surface area both show characteristic scaling trends with respect to cell size that are consistent among different strains. Rapamycin treatment was found to increase vacuole-cell size scaling trends for both volume and surface area. Unexpectedly, these increases did not depend on macroautophagy, as similar increases in vacuole size were observed in the autophagy deficient mutants atg1Δ and atg5Δ. Rather, rapamycin appears to act on vacuole size by inhibiting retrograde membrane trafficking, as the atg18Δ mutant, which is defective in retrograde trafficking, shows similar vacuole size scaling to rapamycin-treated cells and is itself insensitive to rapamycin treatment. Disruption of anterograde membrane trafficking in the apl5Δ mutant leads to complementary changes in vacuole size scaling. These quantitative results lead to a simple model for vacuole size scaling based on proportionality between cell growth rates and vacuole growth rates.
authors.affiliation: Center for Systems and Synthetic Biology and Department of Biochemistry and Biophysics, University of California, San Francisco, California. Electronic address: yhmchan@ucsf.edu.
authors.forename: Yee-Hung Mark
authors.initials: YH
authors.lastname: Chan
authors.affiliation: Center for Systems and Synthetic Biology and Department of Biochemistry and Biophysics, University of California, San Francisco, California. Electronic address: wallace.marshall@ucsf.edu.
authors.forename: Wallace F
authors.initials: WF
authors.lastname: Marshall
mesh_terms: D000465:Algorithms; D001343:Autophagy / Q000187:drug effects / Q000235:genetics; D001692:Biological Transport / Q000187:drug effects / Q000235:genetics; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D048429:Cell Size / Q000187:drug effects; D008954:Models, Biological; D009154:Mutation; D053141:Organelle Size / Q000187:drug effects / Q000235:genetics; D004718:Saccharomycetales / Q000166:cytology* / Q000187:drug effects / Q000235:genetics; D020123:Sirolimus / Q000494:pharmacology; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism*
chemical_list: D020123:Sirolimus