Yeast Genomic Expression Patterns in Response to Low-Shear Modeled Microgravity

The goal of this study was to assess whether low shear-modeled microgravity (LSMMG) effects yeast genomic expression patterns using the powerful tool of whole genome microarray hybridization. We determined changes in the yeast model organism, Saccharomyces cerevisisae, when grown in LSMMG using the rotating High Aspect Ratio Vessel (HARV). A significant number of genes were up- or down-regulated by at least two fold in cells that were grown for 5 generations or 25 generations in HARVs. We identified genes in cell wall integrity signaling pathways containing MAP kinase cascades that may provide clues to novel physiological responses of eukaryotic cells to the external stress of a low-shear modeled microgravity environment. A comparison of the microgravity response to other environmental stress response (ESR) genes showed that 26% of the genes that respond significantly to LSMMG are involved in a general environmental stress response, while 74% of the genes may represent a unique transcriptional response to microgravity. In addition, we found changes in genes involved in budding, cell polarity establishment, and cell separation that confirm our hypothesis that exposure to LSMMG causes changes in gene transcription resulting in a phenotypic response. The results of the study provide interesting clues to potential mechanisms involved in the response to, adaptation to, and survival of eukaryotic cells in a microgravity environment and our findings may have important health implications for human spaceflight. Keywords: time course, stress response, budding, microgravity Four conditions are compared with three replicates each: yeast grown in low-shear modeled microgravity (HARV bioreactor) for 5 and 25 generations; yeast grown in a horizontal (non-LSMMG) HARV bioreactor for 5 and 25 generations.