Divergence in the physiological and transcriptional response to phosphate starvation between related yeast species

Microorganisms encounter a wide variety of environmental stressors depending on the niche they inhabit, such as: nutrient limitation, climate change, or attacks from the human immune system. To survive in these stressful environments, they must adapt. This study looks at nutrient limitation, specifically phosphate starvation, as phosphate is frequently limited in natural environments such as soil, and it is essential for many cellular processes. I identify differences in how four related yeast species, some pathogenic and some non-pathogenic, respond to the lack of phosphate in their environment by comparing key survival strategies such as growth and the ability to store phosphate internally as polyphosphate. For example, species that have more polyphosphate storage experience a quicker recovery benefit and a reduction in environmental stress response because they can use phosphate from the polyphosphate storage. This is important because large amounts of polyphosphate storage were not observed in all species, suggesting that these species have different physiological mechanisms for handling the same stress.

There are also known genetic differences within the phosphate response pathway between species. I looked at regions of the transcription factor Pho4 in two yeast species: Saccharomyces cerevisiae – a non-pathogen, and Candida glabrata – a pathogen, to identify regions that are important for interactions with another transcription factor, Pho2. This dependence is exhibited by disordered regions in both proteins, but not the same region, indicating yet another way in which these yeast species have diverged in their phosphate starvation response. Together, identifying these differences will help improve the understanding of how species adapt to changes in their environment.