The Reduced Level of Inorganic Polyphosphate Mobilizes Antioxidant and Manganese-Resistance Systems in Saccharomyces cerevisiae.

Inorganic polyphosphate (polyP) is crucial for adaptive reactions and stress response in microorganisms. A convenient model to study the role of polyP in yeast is the Saccharomyces cerevisiae strain CRN/PPN1 that overexpresses polyphosphatase Ppn1 with stably decreased polyphosphate level. In this study, we combined the whole-transcriptome sequencing, fluorescence microscopy, and polyP quantification to characterize the CRN/PPN1 response to manganese and oxidative stresses. CRN/PPN1 exhibits enhanced resistance to manganese and peroxide due to its pre-adaptive state observed in normal conditions. The pre-adaptive state is characterized by up-regulated genes involved in response to an external stimulus, plasma membrane organization, and oxidation/reduction. The transcriptome-wide data allowed the identification of particular genes crucial for overcoming the manganese excess. The key gene responsible for manganese resistance is PHO84 encoding a low-affinity manganese transporter: Strong PHO84 down-regulation in CRN/PPN1 increases manganese resistance by reduced manganese uptake. On the contrary, PHM7, the top up-regulated gene in CRN/PPN1, is also strongly up-regulated in the manganese-adapted parent strain. Phm7 is an unannotated protein, but manganese adaptation is significantly impaired in Δphm7, thus suggesting its essential function in manganese or phosphate transport.