Closely related budding yeast species respond to different ecological signals for spore activation

Abstract

Spore activation is one of the most important developmental decisions in fungi as it initiates the transition from dormant and stress‐resistant cells to vegetative cells. Because in many species mating follows spore activation and germination, signals that trigger this developmental transition can also contribute to species reproductive barriers. Here, we examine the biochemical signals triggering spore activation in a natural species complex of budding yeast, Saccharomyces paradoxus (lineages SpA, SpB, SpC and SpC*). We first demonstrate that we can quantitatively monitor spore activation in these closely related lineages. Second, we dissect the composition of culture media to identify components necessary and/or sufficient to activate spores in the four lineages. We show that, contrary to expectation, glucose is necessary but not sufficient to trigger spore activation. We also show that two of the North American lineages (SpC and SpC*) diverge from the other North American (SpB) and European (SpA) lineages in terms of germination signal as their spore activation requires inorganic phosphate. Our results show that the way budding yeast interpret environmental conditions during spore activation diverged among closely related and incipient species, which means that it may play a role in their ecological differentiation and reproductive isolation. Take Away Sensing of multiple compounds allows spore activation in non‐domesticated budding yeast. Spore activation cues differ among Saccharomyces paradoxus lineages. Dextrose and phosphate signal activation in SpC and SpC* spores.

Breaking spore dormancy in budding yeast transforms the cytoplasm and the solubility of the proteome

“…This transition involves multiple changes in cellular state [ 18 ], including the reactivation of multiple metabolic reactions. Although the precise nutrient stimuli that drive germination is dependent on ecological contexts, a carbon source such as glucose is typically an essential signal [ 19 ].…”

Into the wild—Exploring the life cycles of yeasts

“…Depending on the yeast species, such signals include the presence of different carbon sources, temperatures, etc. A paper by Plante and Landry (2020) found that although dextrose is sufficient to trigger spore germination in S. cerevisiae , in certain wild lineages of Saccharomyces paradoxus , dextrose is necessary but not sufficient to trigger spore formation, and inorganic phosphate is also required for the process. These findings highlight the differences in environmental conditions required for two closely related budding yeast species to undergo spore germination.…”