Breaking spore dormancy in budding yeast transforms the cytoplasm and the solubility of the proteome
The biophysical properties of the cytoplasm are major determinants of key cellular processes and adaptation. Many yeasts produce dormant spores that can withstand extreme conditions. Plante et al. show that spores of Saccharomyces cerevisiae exhibit extraordinary biophysical properties, including a highly viscous and acidic cytosol. These conditions alter the solubility of more than 100 proteins such as metabolic enzymes that become more soluble as spores transit to active cell proliferation upon nutrient repletion. A key regulator of this transition is the heat shock protein, Hsp42, which shows transient solubilization and phosphorylation, and is essential for the transformation of the cytoplasm during germination. Germinating spores therefore return to growth through the dissolution of protein assemblies, orchestrated in part by Hsp42 activity. The modulation of spores’ molecular properties are likely key adaptive features of their exceptional survival capacities. The image shows the life cycle of a budding yeast ascospore using false-color transmission electron microscopic images. Clockwise from left: the ascus (blue) containing three developing ascospores; a purified ascospore (purple); a hatching ascospore (red); an elongating ascospore (orange); the first budding of an ascospore (yellow-green), and a vegetative yeast cell (dark green).
Image Credit: Samuel Plante