Fission yeast metabolome dynamics during phosphate starvation and replenishment

Inorganic phosphate is an essential nutrient acquired by cells from their environment and assimilated into myriad intracellular metabolites and macromolecules. Here, we characterize the metabolic responses of fission yeast to a 24 h interval of phosphate starvation, during which cells enter a state of G0 quiescence. Time-resolved profiling revealed that many key phosphometabolites were progressively depleted, including (i) NTPs, NDPs, and dNTPs; (ii) coenzyme A, NAD⁺, NADP⁺, NADH, and ADP-ribose; (iii) glycolysis pathway intermediates upstream of pyruvate; (iv) pentose phosphate pathway intermediates from 6-phosphogluconate to sedoheptulose-7-phosphate; (v) nucleotide sugars GDP-hexose, UDP-glucose/galactose, and UDP-GalNAc/GlcNAc; and (vi) phospholipid precursors glycerol-3-phosphate, CDP-choline, and glycerophosphocholine. By contrast, early Krebs cycle intermediates accumulated during phosphate starvation. Other metabolic changes included the following: (i) interdiction of de novo pyrimidine synthesis; (ii) depletion of S-adenosylmethionine and S-adenosylhomocysteine; (iii) transient accumulation of polyamine biosynthetic intermediates putrescine and 5-methylthioadenosine; (iv) accumulation of betaine (correlating with an increase in expression of atd1 mRNA encoding aldehyde dehydrogenase); and (v) depletion of aminoadipate pathway intermediates 2-oxoadipate, 2-aminoadipate, and saccharopine. Replenishing phosphate after 24 h of starvation resulted in restoration of the pre-starvation metabolome (over 2 to 12 h) as cells exited quiescence and resumed growth.

Fission yeast Schizosaccharomyces pombe is a valuable model system to study cellular phosphate homeostasis and the adaptive responses to chronic phosphate starvation. Previous analyses focused on changes in the fission yeast transcriptome and proteome during phosphate starvation-induced durable G0 quiescence. Here, we deployed metabolomics to survey the scope and temporal order of metabolite changes during 24 h of phosphate starvation and the kinetics of metabolic recovery after cells starved for 24 h are replenished with phosphate. These results contribute to a multi-omics understanding of how phosphate status impacts cell cycle, gene expression, metabolism, and chronological lifespan.