Transcriptional response of Emiliania huxleyi under changing nutrient environments in the North Pacific Subtropical Gyre.

The widespread coccolithophore Emiliania huxleyi is an abundant oceanic phytoplankton, impacting the global cycling of carbon through both photosynthesis and calcification. Here, we examined the transcriptional responses of populations of E. huxleyi in the North Pacific Subtropical Gyre to shifts in the nutrient environment. Using a metatranscriptomic approach, nutrient-amended microcosm studies were used to track the global metabolism of E. huxleyi. The addition of nitrate led to significant changes in transcript abundance for gene pathways involved in nitrogen and phosphorus metabolism, with a decrease in the abundance of genes involved in the acquisition of nitrogen (e.g. N-transporters) and an increase in the abundance of genes associated with phosphate acquisition (e.g. phosphatases). Simultaneously, after the addition of nitrate, genes associated with calcification and genes unique to the diploid life stages of E. huxleyi significantly increased. These results suggest that nitrogen is a major driver of the physiological ecology of E. huxleyi in this system and further suggest that the addition of nitrate drives shifts in the dominant life-stage of the population. Together, these results underscore the importance of phenotypic plasticity to the success of E. huxleyi, a characteristic that likely underpins its ability to thrive across a variety of marine environments.