Pan-proteome regulation of marine Synechococcus nutrient stress plasticity

Variable phytoplankton resource demands can buffer productivity to climate-driven declines in nutrient supply, but the extent of this buffering depends on limits to cellular elemental plasticity. Elemental plasticity is driven by a combination of genomic adaptation and physiological regulation, but their mechanistic links remain unresolved. Here, we combine continuous culture experiments with global proteomics and elemental analyses to determine how genomic diversity shapes nutrient stress plasticity in the globally distributed cyanobacterium Synechococcus. By maintaining fixed growth rates in chemostats under nitrogen- or phosphorus-limiting conditions, we disentangle lineage-specific resource demands from growth effects. All strains show conserved induction of nutrient acquisition pathways, yet strain identity explains most pan-proteome variance, and variation in non-core protein expression predicts deviations in elemental plasticity. Strains from oligotrophic compared to mesotrophic regions exhibit broader proteomic adjustments and wider C:P and N:P ranges. Our findings show that genomic diversity, expressed through pan-proteome regulation, amplifies physiological plasticity and increases phytoplankton nutrient stress buffering capacity under future climate conditions.