Effect of carbon starvation on vacuole number and size in haploid and diploid fission yeast
By: Emily Conrad
Department: Cellular & Molecular Biology
Faculty Advisor: Dr. Mark Chan
Budding yeast subjected to carbon starvation undergo vacuole fusion in both mother and bud, resulting in increased total vacuole volume and surface area and increased average vacuole volume/cell volume and average vacuole surface area/cell volume ratios. In both mother and bud, these values rapidly return to default after re-exposure to glucose, meaning that a homeostatic mechanism for maintaining vacuole-cell size scaling must exist in both of the asymmetrically dividing cells. It is unknown whether fission yeast, which divide medially and near-symmetrically, also exhibit the ability to maintain vacuole size scaling homeostasis after recovery from carbon starvation. Haploid and diploid strains of fission yeast were dyed with FM-4-64 and subjected to sorbitol-substitute media for periods ranging from 45m-2h. Vacuole center-points were annotated in ImageJ, and vacuole volumes and surface areas were calculated using MATLAB. Under visual inspection, vacuoles in fission yeast also appear to fuse under carbon starvation. While vacuole number does decrease in haploids and diploids, average vacuole volume/cell volume and average vacuole surface area/cell volume ratios decrease in both strains. In haploids, total vacuole volume and surface area decrease under carbon starvation, while in diploids, total vacuole volume and surface area increase. Further experiments will investigate whether vacuoles in fission yeast are able to maintain homeostasis upon release from carbon starvation. If so, the two yeasts could share a mechanism for maintaining vacuole size homeostasis.