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.

中文翻译：

---

密切相关的出芽酵母物种对孢子激活的不同生态信号做出反应

孢子激活是真菌最重要的发育决定之一，因为它启动了从休眠和抗逆细胞向营养细胞的转变。因为在许多物种中，孢子激活和萌发后交配，触发这种发育转变的信号也可能导致物种繁殖障碍。在这里，我们检查了在芽殖酵母、Saccharomyces paradoxus（谱系SpA、SpB、SpC和SpC*）的天然物种复合体中触发孢子活化的生化信号）。我们首先证明我们可以定量监测这些密切相关的谱系中的孢子活化。其次，我们剖析培养基的组成，以确定激活四个谱系中孢子所需和/或足够的成分。我们表明，与预期相反，葡萄糖是必要的，但不足以触发孢子激活。我们还表明，两个北美谱系（SpC和SpC*）与其他北美谱系（SpB）和欧洲谱系（SpA ）不同。) 发芽信号方面的谱系，因为它们的孢子活化需要无机磷酸盐。我们的研究结果表明，芽殖酵母在孢子活化过程中解释环境条件的方式在密切相关和初期物种之间存在差异，这意味着它可能在它们的生态分化和生殖隔离中发挥作用。